LT1999-10,20,50 Datasheet

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Datasheet

LT1999-10/LT1999-20/
LT1999-50
1
1999fd
For more information www.linear.com/LT1999
Typical applicaTion
FeaTures DescripTion
High Voltage, Bidirectional
Current Sense Amplifier
The LT
®
1999 is a high speed precision current sense am-
plifier, designed to monitor bidirectional currents over a
wide common mode range. The LT1999 is offered in three
gain options: 10V/V, 20V/V, and 50V/V.
The LT1999 senses current via an external resistive shunt
and generates an output voltage, indicating both magnitude
and direction of the sensed current. The output voltage is
referenced halfway between the supply voltage and ground,
or an external voltage can be used to set the reference
level. With a 2MHz bandwidth and a common mode input
range of –5V to 80V, the LT1999 is suitable for monitor-
ing currents in H-Bridge motor controls, switching power
supplies, solenoid currents, and battery charge currents
from full charge to depletion.
The LT1999 operates from an independent 5V supply
and draws 1.55mA. A shutdown mode is provided for
minimizing power consumption.
The LT1999 is available in an 8-lead SOP, an 8-lead MSOP
(original pinout), or an 8-lead pinout option engineered
for FMEA.
L, LT, LT C , LTM , Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
applicaTions
n Buffered Output with 3 Gain Options:
10V/V, 20V/V, 50V/V
n Gain Accuracy: 0.5% Max
n Input Common Mode Voltage Range: –5V to 80V
n AC CMRR > 80dB at 100kHz
n Input Offset Voltage: 1.5mV Max
n –3dB Bandwidth: 2MHz
n Smooth, Continuous Operation Over Entire Common
Mode Range
n 4kV HBM Tolerant and 1kV CDM Tolerant
n Low Power Shutdown <10µA
n –55°C to 150°C Operating Temperature Range
n 8-Lead MSOP and 8-Lead SO (Narrow) Packages
n 8-Lead MSOP Pinout Option Engineered for FMEA
n High Side or Low Side Current Sensing
n H-Bridge Motor Control
n Solenoid Current Sense
n High Voltage Data Acquisition
n PWM Control Loops
n Fuse/MOSFET Monitoring
Full Bridge Armature Current Monitor
TIME (10µs/DIV)
2.5V
V
OUT
(2V/DIV)
V+IN (20V/DIV)
1999 TA01b
VOUT
V+IN
LT1999
4k
0.8k
160k
160k
2µA
0.8k
4k
SHDN
5V
V+
V+
V+
5V
RS
1999 TA01a
+
+
VS
81
2
3
4
7
6
5
0.1µF
0.1µF
VOUT
RG
V+IN
V–IN
VREF
VSHDN
V+
V+
LT1999-10/LT1999-20/
LT1999-50
2
1999fd
For more information www.linear.com/LT1999
absoluTe MaxiMuM raTings
Differential Input Voltage
+IN toIN (Notes 1, 3) ................................. ±60V, 10ms
+IN to GND, –IN to GND (Note 2) ............. 5.25V to 88V
Total Supply Voltage (V+ to GND) ................................ 6V
Input Voltage Pins 6 and 8 ................... V+ + 0.3V,0.3V
Output Short-Circuit Duration (Note 4) ............ Indefinite
Operating Ambient Temperature (Note 5)
LT1999C ..............................................4C to 85°C
LT1999I ................................................40°C to 8C
LT1999H ............................................ 40°C to 125°C
LT1999MP ......................................... 5C to 150°C
(Note 1)
ORIGINAL MSOP PINOUT
1
2
3
4
V+
+IN
–IN
V+
8
7
6
5
SHDN
OUT
REF
GND
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 150°C, ΘJA = 300°C/W
MSOP PINOUT ENGINEERED FOR FMEA
1
2
3
4
+IN
–IN
NC
V+
8
7
6
5
SHDN
OUT
REF
GND
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 150°C, ΘJA = 300°C/W
1
2
3
4
8
7
6
5
TOP VIEW
SHDN
OUT
REF
GND
V+
+IN
–IN
V+
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 150°C, ΘJA = 190°C/W
pin conFiguraTion
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE
LT1999CMS8-10#PBF LT1999CMS8-10#TRPBF LTFPB 8-Lead Plastic MSOP 0°C to 70°C
LT1999IMS8-10#PBF LT1999IMS8-10#TRPBF LTFPB 8-Lead Plastic MSOP –40°C to 85°C
LT1999HMS8-10#PBF LT1999HMS8-10#TRPBF LTFPB 8-Lead Plastic MSOP –40°C to 125°C
LT1999MPMS8-10#PBF LT1999MPMS8-10#TRPBF LTFQP 8-Lead Plastic MSOP –55°C to 150°C
LT1999CMS8-10F#PBF LT1999CMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout 0°C to 70°C
LT1999IMS8-10F#PBF LT1999IMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout –40°C to 85°C
LT1999HMS8-10F#PBF LT1999HMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout –40°C to 125°C
LT1999MPMS8-10F#PBF LT1999MPMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout –55°C to 150°C
LT1999CS8-10#PBF LT1999CS8-10#TRPBF 199910 8-Lead Plastic SO 0°C to 70°C
LT1999IS8-10#PBF LT1999IS8-10#TRPBF 199910 8-Lead Plastic SO –40°C to 85°C
LT1999HS8-10#PBF LT1999HS8-10#TRPBF 199910 8-Lead Plastic SO –40°C to 125°C
LT1999MPS8-10#PBF LT1999MPS8-10#TRPBF 99MP10 8-Lead Plastic SO –55°C to 150°C
LT1999CMS8-20#PBF LT1999CMS8-20#TRPBF LTFNZ 8-Lead Plastic MSOP 0°C to 70°C
LT1999IMS8-20#PBF LT1999IMS8-20#TRPBF LTFNZ 8-Lead Plastic MSOP –40°C to 85°C
LT1999HMS8-20#PBF LT1999HMS8-20#TRPBF LTFNZ 8-Lead Plastic MSOP –40°C to 125°C
LT1999MPMS8-20#PBF LT1999MPMS8-20#TRPBF LTFQQ 8-Lead Plastic MSOP –55°C to 150°C
Specified Temperature Range (Note 6)
LT1999C .................................................. C to 70°C
LT1999I ................................................40°C to 8C
LT1999H ............................................ 40°C to 125°C
LT1999MP ......................................... 5C to 150°C
Junction Temperature ........................................... 150°C
Storage Temperature Range .................. 6C to 150°C
LT1999-10/LT1999-20/
LT1999-50
3
1999fd
For more information www.linear.com/LT1999
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, 0°C < TA < 70°C for C-grade parts, –40°C < TA < 85°C for I-grade parts, and –40°C < TA < 125°C for H-grade parts, otherwise
specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V, VREF = floating, VSHDN = floating, unless otherwise specified. See Figure 2.
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE
LT1999CMS8-20F#PBF LT1999CMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout 0°C to 70°C
LT1999IMS8-20F#PBF LT1999IMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout –40°C to 85°C
LT1999HMS8-20F#PBF LT1999HMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout –40°C to 125°C
LT1999MPMS8-20F#PBF LT1999MPMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout –55°C to 150°C
LT1999CS8-20#PBF LT1999CS8-20#TRPBF 199920 8-Lead Plastic SO 0°C to 70°C
LT1999IS8-20#PBF LT1999IS8-20#TRPBF 199920 8-Lead Plastic SO –40°C to 85°C
LT1999HS8-20#PBF LT1999HS8-20#TRPBF 199920 8-Lead Plastic SO –40°C to 125°C
LT1999MPS8-20#PBF LT1999MPS8-20#TRPBF 99MP20 8-Lead Plastic SO –55°C to 150°C
LT1999CMS8-50#PBF LT1999CMS8-50#TRPBF LTFPC 8-Lead Plastic MSOP 0°C to 70°C
LT1999IMS8-50#PBF LT1999IMS8-50#TRPBF LTFPC 8-Lead Plastic MSOP –40°C to 85°C
LT1999HMS8-50#PBF LT1999HMS8-50#TRPBF LTFPC 8-Lead Plastic MSOP –40°C to 125°C
LT1999MPMS8-50#PBF LT1999MPMS8-50#TRPBF LTFQR 8-Lead Plastic MSOP –55°C to 150°C
LT1999CMS8-50F#PBF LT1999CMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout 0°C to 70°C
LT1999IMS8-50F#PBF LT1999IMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout –40°C to 85°C
LT1999HMS8-50F#PBF LT1999HMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout –40°C to 125°C
LT1999MPMS8-50F#PBF LT1999MPMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout –55°C to 150°C
LT1999CS8-50#PBF LT1999CS8-50#TRPBF 199950 8-Lead Plastic SO 0°C to 70°C
LT1999IS8-50#PBF LT1999IS8-50#TRPBF 199950 8-Lead Plastic SO –40°C to 85°C
LT1999HS8-50#PBF LT1999HS8-50#TRPBF 199950 8-Lead Plastic SO –40°C to 125°C
LT1999MPS8-50#PBF LT1999MPS8-50#TRPBF 99MP50 8-Lead Plastic SO –55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
orDer inForMaTion
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VSENSE Full-Scale Input Sense Voltage (Note 7)
VSENSE = V+IN – V–IN
LT1999-10
LT1999-20
LT1999-50
l
l
l
–0.35
–0.2
–0.08
0.35
0.2
0.08
V
V
V
VCM CM Input Voltage Range l–5 80 V
RIN(DIFF) Differential Input Impedance ΔVINDIFF = ±2V/Gain l6.4 8 9.6
RINCM CM Input Impedance ΔVCM = 5.5V to 80V
ΔVCM = –5V to 4.5V
l
l
5
3.6
20
4.8
6
VOSI Input Referred Voltage Offset
l
–750
–1500
±500 750
1500
μV
μV
ΔVOSI /ΔT Input Referred Voltage Offset Drift 5 μV/°C
AVGain LT1999-10
LT1999-20
LT1999-50
l
l
l
9.95
19.9
49.75
10
20
50
10.05
20.1
50.25
V/V
V/V
V/V
AV Error Gain Error ΔVOUT = ±2V l–0.5 ±0.2 0.5 %
LT1999-10/LT1999-20/
LT1999-50
4
1999fd
For more information www.linear.com/LT1999
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, 0°C < TA < 70°C for C-grade parts, –40°C < TA < 85°C for I-grade parts, and –40°C < TA < 125°C for H-grade parts, otherwise
specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V, VREF = floating, VSHDN = floating, unless otherwise specified. See Figure 2.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
IBInput Bias Current
I(+IN) = I(–IN)
(Note 8)
VCM > 5.5V
VCM = –5V
VSHDN = 0.5V, 0V < VCM < 80V
l
l
l
100
–2.35
137.5
–1.95
0.001
175
–1.5
2.5
μA
mA
μA
IOS Input Offset Current
IOS = I(+IN) – I(–IN)
(Note 8)
VCM > 5.5V
VCM = –5V
VSHDN = 0.5V, 0V < VCM < 80V
l
l
l
–1
–10
–2.5
1
10
2.5
μA
μA
μA
PSRR Supply Rejection Ratio V+ = 4.5V to 5.5V l68 77 dB
CMRR Sense Input Common Mode Rejection VCM = –5V to 80V
VCM = –5V to 5.5V
VCM = 12V, 7VP-P, f = 100kHz,
VCM = 0V, 7VP-P, f = 100kHz
l
l
l
l
96
96
75
80
105
120
90
100
dB
dB
dB
dB
enDifferential Input Referred Noise Voltage Density f = 10kHz
f = 0.1Hz to 10Hz
97
8
nV/√Hz
μVP-P
REFRR REF Pin Rejection, V+ = 5.5V
ΔVREF = 3.0V
ΔVREF = 3.25V
ΔVREF = 3.25V
LT1999-10
LT1999-20
LT1999-50
l
l
l
62
62
62
70
70
70
dB
dB
dB
RREF REF Pin Input Impedance
VSHDN = 0.5V
l
l
60
0.15
80
0.4
100
0.65
VREF Open Circuit Voltage
VSHDN = 0.5V
l
l
2.45
1
2.5
2.5
2.55
2.75
V
V
VREFR REF Pin Input Range (Note 9) LT1999-10
LT1999-20
LT1999-50
l
l
l
1.25
1.125
1.125
V+ – 1.25
V+ – 1.125
V+ – 1.125
V
V
V
ISHDN Pin Pull-Up Current V+ = 5.5V, VSHDN = 0V l–6 –2 μA
VIH SHDN Pin Input High lV+ – 0.5 V
VIL SHDN Pin Input Low l0.5 V
f3dB Small Signal Bandwidth LT1999-10
LT1999-20
LT1999-50
2
2
1.2
MHz
MHz
MHz
SR Slew Rate 3 V/μs
tsSettling Time due to Input Step, ΔVOUT = ±2V 0.5% Settling 2.5 μs
trCommon Mode Step Recovery Time
ΔVCM = ±50V, 20ns
(Note 10)
LT1999-10
LT1999-20
LT1999-50
0.8
1
1.3
μs
μs
μs
VSSupply Voltage (Note 11) l4.5 5 5.5 V
ISSupply Current VCM > 5.5V
VCM = –5V
V+ = 5.5V, VSHDN = 0.5V, VCM > 0V
l
l
l
1.55
5.8
3
1.9
7.1
10
mA
mA
μA
ROOutput Impedance ΔIO = ±2mA 0.15 Ω
ISRC Sourcing Output Current RLOAD = 50Ω to GND l6 31 40 mA
ISNK Sinking Output Current RLOAD = 50Ω to V+l15 26 40 mA
VOUT Swing Output High (with Respect to V+) RLOAD = 1kΩ to Mid-Supply
RLOAD = Open
l
l
125
5
250
125
mV
mV
Swing Output Low (with Respect to V) RLOAD = 1kΩ to Mid-Supply
RLOAD = Open
l
l
250
150
400
225
mV
mV
tON Turn-On Time VSHDN = 0V to 5V 1 μs
tOFF Turn-Off Time VSHDN = 5V to 0V 1 μs
LT1999-10/LT1999-20/
LT1999-50
5
1999fd
For more information www.linear.com/LT1999
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, –55°C < TA < 150°C for MP-grade parts, otherwise specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V,
VREF = floating, VSHDN = floating, unless otherwise specified. See Figure 2.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VSENSE Full-Scale Input Sense Voltage (Note 7)
VSENSE = V+IN – V–IN
LT1999-10
LT1999-20
LT1999-50
l
l
l
–0.35
–0.2
–0.08
0.35
0.2
0.08
V
V
V
VCM CM Input Voltage Range l–5 80 V
RIN(DIFF) Differential Input Impedance ΔVINDIFF = ±2V/GAIN l6.4 8 9.6
RINCM CM Input Impedance ΔVCM = 5.5V to 80V
ΔVCM = –5V to 4.5V
l
l
5
3.6
20
4.8
6
VOSI Input Referred Voltage Offset
l
–750
–2000
±500 750
2000
μV
μV
ΔVOSI/ΔT Input Referred Voltage Offset Drift 8 μV/°C
AVGain LT1999-10
LT1999-20
LT1999-50
l
l
l
9.95
19.9
49.75
10
20
50
10.05
20.1
50.25
V/V
V/V
V/V
AV Error Gain Error ΔVOUT = ±2V l–0.5 ±0.2 0.5 %
IBInput Bias Current
I(+IN) = I(–IN)
(Note 8)
VCM > 5.5V
VCM = –5V
VSHDN = 0.5V, 0V < VCM < 80V
l
l
l
100
–2.35
137.5
–1.95
0.001
180
–1.5
10
μA
mA
μA
IOS Input Offset Current
IOS = I(+IN) – I(–IN)
(Note 8)
VCM > 5.5V
VCM = –5V
VSHDN = 0.5V, 0V < VCM < 80V
l
l
l
–1
–10
–10
1
10
10
μA
μA
μA
PSRR Supply Rejection Ratio V+ = 4.5V to 5.5V l68 77 dB
CMRR Sense Input Common Mode Rejection VCM = –5V to 80V
VCM = –5V to 5.5V
VCM = 12V, 7VP-P, f = 100kHz,
VCM = 0V, 7VP-P, f = 100kHz
l
l
l
l
96
96
75
80
105
120
90
100
dB
dB
dB
dB
enDifferential Input Referred Noise Voltage Density f= 10kHz
f = 0.1Hz to 10Hz
97
8
nV/√Hz
μVP-P
REFRR REF Pin Rejection, V+ = 5.5V
ΔVREF = 2.75V
ΔVREF = 3.25V
ΔVREF = 3.25V
LT1999-10
LT1999-20
LT1999-50
l
l
l
62
62
62
70
70
70
dB
dB
dB
RREF REF Pin Input Impedance
VSHDN = 0.5V
l
l
60
0.15
80
0.4
100
0.65
VREF Open Circuit Voltage
VSHDN = 0.5V
l
l
2.45
0.25
2.5
2.5
2.55
2.75
V
V
VREFR REF Pin Input Range (Note 9) LT1999-10
LT1999-20
LT1999-50
l
l
l
1.5
1.125
1.125
V+ – 1.25
V+ – 1.125
V+ – 1.125
V
V
V
ISHDN Pin Pull-Up Current V+ = 5.5V, VSHDN = 0V l–6 –2 μA
VIH SHDN Pin Input High lV+ – 0.5 V
VIL SHDN Pin Input Low l0.5 V
f3dB Small Signal Bandwidth LT1999-10
LT1999-20
LT1999-50
2
2
1.2
MHz
MHz
MHz
SR Slew Rate 3 V/μs
tSSettling Time Due to Input Step, ΔVOUT = ±2V 0.5% Settling 2.5 μs
LT1999-10/LT1999-20/
LT1999-50
6
1999fd
For more information www.linear.com/LT1999
elecTrical characTerisTics
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: Pin 2 (+IN) and Pin 3 (–IN) are protected by ESD voltage clamps
which have asymmetric bidirectional breakdown characteristics with respect
to the GND pin (Pin 5). These pins can safely support common mode
voltages which vary from –5.25V to 88V without triggering an ESD clamp.
Note 3: Exposure to differential sense voltages exceeding the normal
operating range for extended periods of time may degrade part
performance. A heat sink may be required to keep the junction temperature
below the Absolute Maximum Rating when the inputs are stressed
differentially. The amount of power dissipated in the LT1999 due to input
overdrive can be approximated by:
P
DISS =V+IN VIN
( )
2
8kΩ
Note 4: A heat sink may be required to keep the junction temperature
below the absolute maximum rating.
Note 5: The LT1999C/LT1999I are guaranteed functional over the operating
temperature range –40°C to 85°C. The LT1999H is guaranteed functional
over the operating temperature range –40°C to 125°C. The LT1999MP is
guaranteed functional over the operating temperature range –55°C to 150°C.
Junction temperatures greater than 125°C will promote accelerated aging.
The LT1999 has a demonstrated typical life beyond 1000 hours at 150°C.
Note 6: The LT1999C is guaranteed to meet specified performance from
0°C to 70°C. The LT1999C is designed, characterized, and expected to
meet specified performance from –40°C to 85°C but is not tested or
QA sampled at these temperatures. The LT1999I is guaranteed to meet
specified performance from –40°C to 85°C. The LT1999H is guaranteed
to meet specified performance from –40°C to 125°C. The LT1999MP is
guaranteed to meet specified performance from –55°C to 150°C.
Note 7: Full-scale sense (VSENSE) gives indication of the maximum
differential input that can be applied with better than 0.5% gain accuracy.
Gain accuracy is degraded when the output saturates against either power
supply rail. VSENSE is verified with V+ = 5.5V, VCM = 12V, with the REF pin
set to it’s voltage range limits. The maximum VSENSE is verified with the
REF pin set to it’s minimum specified limit, verifying the gain error is less
than 0.5% at the output. The minimum VSENSE is verified with the REF pin
set to its maximum specified limit, verifying the gain error at the output is
less than 0.5%. See Note 9 for more information.
Note 8: IB is defined as the average of the input bias currents to the +IN
and –IN pins (Pins 2 and 3). A positive current indicates current flowing
into the pin. IOS is defined as the difference of the input bias currents.
IOS = I(+IN) – I(–IN)
Note 9: The REF pin voltage range is the minimum and maximum limits
that ensures the input referred voltage offset does not exceed ±3mV over
the I, C, and H temperature ranges, and ±3.5mV over the MP temperature
range.
Note 10: Common mode recovery time is defined as the time it takes the
output of the LT1999 to recover from a 50V, 20ns input common mode
voltage transition, and settle to within the DC amplifier specifications.
Note 11: Operating the LT1999 with V+ < 4.5V is possible, although the
LT1999 is not tested or specified in this condition. See the Applications
Information section.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
trCommon Mode Step Recovery Time
ΔVCM = ±50V, 20ns
(Note 10)
LT1999-10
LT1999-20
LT1999-50
0.8
1
1.3
μs
μs
μs
VSSupply Voltage (Note 11) l4.5 5 5.5 V
ISSupply Current VCM > 5.5V
VCM = –5V
V+ = 5.5V, VSHDN = 0.5V, VCM > 0V
l
l
l
1.55
5.8
3
1.9
7.1
25
mA
mA
μA
ROOutput Impedance ΔIO = ±2mA 0.15 Ω
ISRC Sourcing Output Current RLOAD = 50Ω to GND l3 31 40 mA
ISNK Sinking Output Current RLOAD = 50Ω to V+l10 26 40 mA
VOUT Swing Output High (with Respect to V+) RLOAD = 1kΩ to Mid-Supply
RLOAD = Open
l
l
125
5
250
125
mV
mV
Swing Output Low (with Respect to V) RLOAD = 1kΩ to Mid-Supply
RLOAD = Open
l
l
250
150
400
225
mV
mV
tON Turn-On Time VSHDN = 0V to 5V 1 μs
tOFF Turn-Off Time VSHDN = 5V to 0V 1 μs
The l denotes the specifications which apply over the full operating
temperature range, –55°C < TA < 150°C for MP-grade parts, otherwise specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V,
VREF = floating, VSHDN = floating, unless otherwise specified. See Figure 2.
LT1999-10/LT1999-20/
LT1999-50
7
1999fd
For more information www.linear.com/LT1999
Typical perForMance characTerisTics
Input Bias Current
vs Input Common Mode Input Bias Current vs Temperature
Input Impedance
vs Input Common Mode Voltage
VCM (V)
–5
IB (mA)
0.5
0
–1.0
–1.5
–0.5
–2.0 4525 65
1999 G07
75 8035155 55
V+ = 5V
TEMPERATURE (°C)
–55
IB (µA)
144
140
134
136
138
142
132 70
20 120
1999 G08
14545–5–30 95
VCM = 80V
VCM = 5.5V
VSHDN = OPEN
VINDIFF = 0V
V+ = 5V
VCM (V)
–5
IMPEDANCE (kΩ)
100000
10000
100
10
1000
14525 65
1999 G09
7535155 55
COMMON MODE INPUT
IMPEDANCE
DIFFERENTIAL INPUT IMPEDANCE
Supply Current
vs SHDN Pin Voltage
Shutdown Supply Current
vs Temperature
Shutdown Input Bias Current
vs Input Common Mode
Supply Current
vs Input Common Mode Supply Current vs Temperature Supply Current vs Supply Voltage
VCM (V)
–5
IS (mA)
7
6
4
2
5
3
1
04525 65
1999 G01
75 8035155 55
V+ = 5V
TEMPERATURE (°C)
–55
IS (mA)
1.8
1.7
1.5
1.6
1.4 7020 120
1999 G02
14545–5–30 95
V+ = 5.5V
V+ = 4.5V
VSHDN = OPEN
VINDIFF = 0V
VCM = 12V
SUPPLY VOLTAGE (V)
0
I
S
(mA)
4.0
3.0
1.0
2.0
3.5
1.5
2.5
0
0.5
2 4
1999 G03
51 3
VCM = 12V
150°C
130°C
90°C
25°C
–45°C
–55°C
VSHDN (V)
0
IS (mA)
10
0.1
1
0.001
0.01
2 4
1999 G04
51 3
TA = 25°C
TA = 150°C
TA = –55°C
V+ = 5V
VCM = 12V
TEMPERATURE (°C)
–55
IS (µA)
10
8
4
2
6
07020 120
1999 G05
14545–5–30 95
V+ = 5.5V
V+ = 4.5V
VSHDN = 0V
VINDIFF = 0V
VCM = 12V
VCM (V)
0
I
B
(nA)
1000
10
100
140 80
1999 G06
10020 60
V+ = 5V
VSHDN = 0V
VSENSE = 0V
TA = 70°C
TA = 90°C
TA = 150°C
TA =110°C
TA =130°C
LT1999-10/LT1999-20/
LT1999-50
8
1999fd
For more information www.linear.com/LT1999
Typical perForMance characTerisTics
LT1999-10 Small Signal
Frequency Response
Gain Error vs Temperature
Gain Error
vs Input Common Mode Voltage
Input Referred Voltage Offset
vs Temperature and Gain Option
Input Referred Voltage Offset
vs Input Common Mode Voltage
TEMPERATURE (°C)
–55
VOSI (µV)
1500
1000
–500
–1000
500
0
–1500 7020 120
1999 G10
14545–5–30 95
LT1999-10
LT1999-20
LT1999-50
VCM = 12V
12 UNITS PLOTTED
VCM (V)
–5
VOSI (µV)
1500
1000
–500
–1000
500
0
–1500 4525 65
1999 G11
7535155 55
V+ = 5V
TA = 25°C
12 UNITS PLOTTED
LT1999-10
LT1999-20
LT1999-50
TEMPERATURE (°C)
–55
GAIN ERROR (%)
0.50
0.25
–0.25
0
–0.50 7020 120
1999 G15
14545–5–30 95
VCM = 12V
12 UNITS PLOTTED
LT1999-10
LT1999-20
LT1999-50
VCM (V)
–5
GAIN ERROR (%)
0.50
0.25
–0.25
0
–0.50 4525 65
1999 G16
7535155 55
V+ = 5V
TA = 25°C
12 UNITS PLOTTED
LT1999-10
LT1999-20
LT1999-50
FREQUENCY (kHz)
1
GAIN (dB)
PHASE (DEG)
30
15
0
–5
10
25
20
5
–10
180
45
–90
–135
0
135
90
–45
–180
10 1000
1999 G12
10000100
VOUT = 0.5VP-P AT 1kHz
GAIN
PHASE
LT1999-50 Small Signal
Frequency Response
LT1999-20 Small Signal
Frequency Response
FREQUENCY (kHz)
1
GAIN (dB)
PHASE (DEG)
35
20
5
0
15
30
25
10
–5
180
45
–90
–135
0
135
90
–45
GAIN
–180
10 1000
1999 G13
10000100
VOUT = 0.5VP-P AT 1kHz
PHASE
FREQUENCY (kHz)
1
GAIN (dB)
PHASE (DEG)
40
25
10
5
20
35
30
15
0
180
45
–90
–135
0
135
90
–45
GAIN
PHASE
–180
10 1000
1999 G14
10000100
VOUT = 0.5VP-P AT 1kHz
LT1999-10/LT1999-20/
LT1999-50
9
1999fd
For more information www.linear.com/LT1999
Typical perForMance characTerisTics
CMRR vs FrequencyCMRR vs Frequency
FREQUENCY (kHz)
1
CMRR (dB)
120
100
80
20
40
60
01000
1999 G23
1000010010
VCM = 12V
V+ = 5V
TA = 25°C
6 UNITS PLOTTED
LT1999-10
LT1999-20
LT1999-50
LT1999-50 2V Step Response
Settling Time
LT1999-10 2V Step Response
Settling Time
LT1999-20 2V Step Response
Settling Time
LT1999-50 Pulse Response
TIME (2µs/DIV)
V
SENSE
(0.1V/DIV)
V
OUT
(1V/DIV)
1999 G19
VOUT
VSENSE
VOUT
TIME (1µs/DIV)
VOUT (V)
OUTPUT ERROR (V)
4.5
3.5
1.5
2.5
0.5
4.0
2.0
3.0
1.0
0.100
0.050
–0.050
0
–0.100
0.075
–0.025
0.025
–0.075
1999 G20
OUTPUT ERROR
VOUT
VOUT (V)
OUTPUT ERROR (V)
4.5
3.5
1.5
2.5
0.5
4.0
2.0
3.0
1.0
0.20
0.10
–0.01
0
–0.20
0.15
–0.05
0.05
–0.15
OUTPUT ERROR
TIME (1µs/DIV)
–1 42 6
1999 G21
7310 5 9 108
VOUT (V)
OUTPUT ERROR (V)
4.5
3.5
1.5
2.5
0.5
4.0
2.0
3.0
1.0
0.500
0.250
–0.250
0
–0.500
0.375
–0.125
0.125
–0.375
TIME (1µs/DIV) 1999 G22
VOUT
OUTPUT ERROR
LT1999-10 Pulse Response LT1999-20 Pulse Response
TIME (2µs/DIV)
VSENSE (0.5V/DIV)
V
OUT
(1V/DIV)
1999 G17
VOUT
VSENSE
TIME (2µs/DIV)
VSENSE (0.2V/DIV)
V
OUT
(1V/DIV)
1999 G18
VOUT
VSENSE
FREQUENCY (kHz)
1
CMRR (dB)
120
100
80
20
40
60
01000100
1999 G24
1000010
VCM = 0V
V+ = 5V
TA = 25°C
6 UNITS PLOTTED
LT1999-10
LT1999-20
LT1999-50
LT1999-10/LT1999-20/
LT1999-50
10
1999fd
For more information www.linear.com/LT1999
LT1999-10 Common Mode Rising
Edge Step Response
VOUT (0.5V/DIV)
VCM (25V/DIV)
TIME (0.5µs/DIV) 1999 G25
VCM, tRISE ≈ 20ns
VOUT
LT1999-10 Common Mode Falling
Edge Step Response
VOUT (0.5V/DIV)
VCM (25V/DIV)
TIME (0.5µs/DIV) 1999 G26
VCM, tFALL ≈ 20ns
VOUT
VOUT (0.5V/DIV)
V
CM
(25V/DIV)
TIME (0.5µs/DIV) 1999 G27
VCM, tRISE ≈ 20ns
VOUT
LT1999-20 Common Mode Rising
Edge Step Response
LT1999-20 Common Mode Falling
Edge Step Response
V
OUT
(0.5V/DIV)
VCM (25V/DIV)
TIME (0.5µs/DIV) 1999 G28
VCM, tFALL ≈ 20ns
VOUT
Typical perForMance characTerisTics
LT1999-50 Common Mode Rising
Edge Step Response
LT1999-50 Common Mode Falling
Edge Step Response
VOUT (0.5V/DIV)
VCM (25V/DIV)
TIME (0.5µs/DIV) 1999 G29
LT1999-50 Common Mode Rising Edge
Step Response
TIME (0.5 s / div)
VOUT (0.5 V / div)
VCM (25V / div)
VCM
tRISE20ns
VCM, tRISE ≈ 20ns
VOUT
VOUT (0.5V/DIV)
VCM (25V/DIV)
TIME (0.5µs/DIV) 1999 G30
VCM, tFALL ≈ 20ns
VOUT
LT1999-10/LT1999-20/
LT1999-50
11
1999fd
For more information www.linear.com/LT1999
Typical perForMance characTerisTics
LT1999 Input Referred Noise
Density vs Frequency
FREQUENCY (kHz)
0.001 0.01 0.1
NOISE DENSITY (nV/√Hz)
1000
100
10 1000
1999 G31
10000101
TEMPERATURE (°C)
–55
ISC (mA)
40
20
30
10
–20
0
–40
–10
–30
7020 120
1999 G32
14545–5–30 95
SINKING
SOURCING
TEMPERATURE (°C)
–55
REF PIN VOLTAGE (V)
3.0
2.5
1.0
2.0
0
1.5
0.5
7020 120
1999 G33
14545–5–30 95
SHDN MODE
ACTIVE MODE
V+ = 5V
Short-Circuit Current
vs Temperature
REF Open Circuit Voltage
vs Temperature
SHDN Pin Current vs SHDN Pin
Voltage and Temperature
Turn-On/Turn-Off Time
vs SHDN Voltage
VOUT vs VSENSE
IS (1mA/DIV)
SHDN PIN VOLTAGE (5V/DIV)
TIME (1µs/DIV) 1999 G35
VSHDN
IS
SHUTDOWN
VCM = 12V
VSENSE (V)
–0.25
VOUT (V)
6
4
5
1
2
3
–1 –0.05 0.15
1999 G36
0.25–0.15 0.05
VREF = 2.5V
LT1999-10
LT1999-20
LT1999-50
0
VSHDN (V)
0
I
SHDN
(µA)
–2
–4
–1
0
–3
2 4 5
1999 G34
1 3
TA = 150°C
TA = 25°C
TA = –55°C
V+ = 5V
VCM = 12V
VOUT vs VSENSE Over the Sense
ABSMAX Range
VSENSE (V)
–60
VOUT (V)
6
4
5
1
2
3
–1 –30 30
1999 G37
600
0
VOUT PHASE REVERSAL FOR VSENSE < –25V
VREF = 2.5V
LT1999-10
LT1999-20
LT1999-50
LT1999-10/LT1999-20/
LT1999-50
12
1999fd
For more information www.linear.com/LT1999
pin FuncTions
V+ (Pins 1, 4/Pin 4): Power Supply Voltage. Pins 1 and 4
are tied internally together. The specified range of opera-
tion is 4.5V to 5.5V, but lower supply voltages (down to
approximately 4V) is possible although the LT1999 is not
tested or characterized below 4.5V. See the Applications
Information section.
+IN (Pin 2/Pin 1): Positive Sense Input Pin.
–IN (Pin 3/Pin 2): Negative Sense Input Pin.
NC (NA/Pin 3)
GND (Pin 5/Pin 5): Ground Pin.
REF (Pin 6/Pin 6): Reference Pin Input. The REF pin sets
the output common mode level and is set halfway between
V+ and GND using a divider made of two 160k resistors. The
default open circuit potential of the REF pin is mid-supply.
It can be overdriven by an external voltage source cable
of driving 80k to a mid-supply potential (see the Electrical
Characteristics table for its specified input voltage range).
OUT (Pin 7/Pin 7): Voltage Output. VOUT = AV(VSENSE ±
VOSI), where AV is the gain, and VOSI is the input referred
offset voltage. The output amplifier has a low impedance
output and is designed to drive up to 200pF capacitive
loads directly. Capacitive loads exceeding 200pF should
be decoupled with an external resistor of at least 100Ω.
SHDN (Pin 8/Pin 8): Shutdown Pin. When pulled to within
0.5V of GND (Pin 5), will place the LT1999 into low power
shutdown. If the pin is left floating, an internalA pull-
up current source will place the LT1999 into the active
(amplifying) state.
(LT1999-XX/LT1999-XXF)
LT1999-10/LT1999-20/
LT1999-50
13
1999fd
For more information www.linear.com/LT1999
SHDN
V+
V+
V+
V+
160k
160k
1999 BD
2µA
LT1999-XXF
+
+
RG
0.8k
4k
0.8k
8
7
2
1
3
4
6
5
4k
NC
SHDN
V+
V+
V+
V+
V+
160k
160k
1999 BD
2µA
LT1999
+
+
RG
0.8k
4k
0.8k
8
7
2
1
3
4
6
5
4k
block DiagraM
Figure 1. Simplified Block Diagram
TesT circuiT
5V
1999 F02
0.1µF
VOUT
VIN(DIFF)
+
VCM
VREF
VSHDN
+
+
+
LT1999F
4k
0.8k
160k
160k
2µA
0.8k
4k
NC
SHDN
V+
V+
+
+
8
1
2
3
4
7
6
5
RG
0.1µF
V+
V+
5V
5V
1999 F02
0.1µF
VOUT
VIN(DIFF)
+
VCM VREF
VSHDN
+
+
+
LT1999
4k
0.8k
160k
160k
2µA
0.8k
4k
SHDN
V+
V+
V+
+
+
8
2
1
3
4
7
6
5
RG
0.1µF
V+
V+
Figure 2. Test Circuit
LT1999-10/LT1999-20/
LT1999-50
14
1999fd
For more information www.linear.com/LT1999
The LT1999 current sense amplifier provides accurate
bidirectional monitoring of current through a user-selected
sense resistor. The voltage generated by the current flowing
in the sense resistor is amplified by a fixed gain of 10V/V,
20V/V or 50V/V (LT1999-10, LT1999-20, or LT1999-50
respectively) and is level shifted to the OUT pin. The volt-
age difference and polarity of the OUT pin with respect
to REF (Pin 6) indicates magnitude and direction of the
current in the sense resistor.
THEORY OF OPERATION
Refer to the Block Diagram (Figure 1).
Case 1: V+ < VCM < 80V
For input common mode voltages exceeding the power
supply, one can assume D1 of Figure 1 is completely off.
The sensed voltage (VSENSE) is applied across Pin 2 (+IN)
and Pin 3 (–IN) to matched resistors R+IN and RIN (nomi-
nally 4k each). The opposite ends of R+IN and RIN are
forced to equal potentials by transconductor GIN, which
convert the differentially sensed voltage into a sensed
current. The sensed current in R+IN and RIN is combined,
level-shifted, and converted back into a voltage by trans-
resistance amplifier AO and resistor RG. Amplifier AO pro-
vides high open loop gain to accurately convert the sensed
current back into a voltage and to drive external loads. The
theoretical output voltage is determined by the sensed
voltage (VSENSE), and the ratio of two on-chip resistors:
VOUT VREF =VSENSE
R
G
R
IN
where
RIN =
R
+IN
+R
IN
2
nominally 4k
For the LT1999-10, RG is nominally 40k. For the LT1999-20,
RG is nominally 80k, and for the LT1999-50, RG is nomi-
nally 200k.
applicaTions inForMaTion
The voltage difference between the OUT pin and the REF
pin represent both polarity and magnitude of the sensed
voltage. The noninverting input of amplifier AO is biased
by a resistive 160k to 160k divider tied between V+ and
GND to set the default REF pin bias to mid-supply.
Case 2: –5V < VCM < V+
For common mode inputs which transition or are set below
the supply voltage, diode D1 will turn on and will provide a
source of current through R+S and RS to bias the inputs
of transconductance amplifier GIN at least 2.25V above
GND. The transition is smooth and continuous; there are
negligible changes to either gain or amplifier voltage off-
set. The only difference in amplifier operation is the bias
currents provided by D1 through R+S and RS are steered
through the input pins, otherwise amplifier operation is
identical. The inputs to transconductance amplifier GIN are
still forced to equal potentials forcing any differential volt-
ages appearing at the +IN andIN pins into a differential
current. This differential current is combined, level-shifted,
and converted back into a voltage by trans-resistance
amplifier AO and Resistor RG. Resistors R+S and RS are
trimmed to match R+IN and RIN respectively, to prevent
common mode to differential conversion from occurring
(to the extent of the matched trim) when the input com-
mon mode transitions below V+.
As described in case 1, the output is determined by the
sense voltage and the ratio of two on-chip resistors:
VOUT VREF =VSENSE
R
G
R
IN
where
RIN =
R
+IN
+R
IN
2
LT1999-10/LT1999-20/
LT1999-50
15
1999fd
For more information www.linear.com/LT1999
applicaTions inForMaTion
Input Common Mode Range
The LT1999 was optimized for high common mode re-
jection. Its input stage is balanced and fully differential,
designed to amplify differential signals and reject common
mode signals. There is negligible crossover distortion due
to sense voltage reversals. The amplifier is most linear in
the zero-sense region.
With the V+ supply configured within the specified and
tested range (4.5V < V+ < 5.5V), the LT1999’s common
mode range extends from –5V to 80V. Pushing +IN and
–IN beyond the limits specified in the Absolute Maximum
table can turn on the voltage clamps designed to protect
the +IN and –IN pins during ESD events.
It is possible to operate the LT1999 on power supplies
as low as 4V (although it is not tested or specified below
4.5V). Operating the LT1999 on supplies below 4V will
produce erratic behavior. When operating the LT1999
with supplies as low as 4V, the common mode range for
inputs which extend below GND is reduced. Refer to the
Block Diagram (Figure 1). For inputs driven below V+,
diode D1 conducts. For proper operation, the input to the
transconductor V(G+IN) must be biased at approximately
2.25V above the GND pin. V(G+IN) sits on the centertap
of a voltage divider comprised of R+S and R+IN V(GIN)
likewise sits in the middle of the voltage divider comprised
of RS , and RIN). The voltage on V(G+IN) input is given
by the following equation:
V(G+IN)=V+IN
R
+S
R
+S
+R
+IN
+V+VD1
( )
R
+IN
R
+S
+R
+IN
Setting V(G+IN) = 2.25V, the ratio (R+IN/R+S) to 5, and VD1
equal to 0.8V (cold temperatures), a plot of the lower input
common mode range plotted against supply is shown in
Figure 3.
Output Common Mode Range
The LT1999’s output common mode level is set by the
voltage on the REF pin. The REF pin sits in the middle of
a 160k to 160k voltage divider connected between V+ and
GND which sets the default open circuit potential of the
REF pin to mid-supply. It can be overdriven by an external
voltage source capable of driving 80k tied to a mid-supply
potential. See the Electrical Characteristics table for the
REF pin’s specified input voltage range.
Differential sampling of the OUT pin with respect the REF
pin provides the best noise immunity. Measurements of
the output voltage made differentially with respect to the
REF pin will provide the highest power supply and com-
mon mode rejection. Otherwise, power supply or GND pin
disturbances are divided by the REF pin’s voltage divider
and appear directly at the noninverting input of the trans-
resistance amplifier AO and are not rejected.
If not driven by a low impedance (<100Ω), the REF pin
should be filtered with at least 1nF of capacitance to a
low impedance, low noise ground plane. This external
capacitance will also provide a charge reservoir during
high frequency sampling of the REF pin by ADC inputs
attached to this pin.
Figure 3. Lower Input Common Mode vs Supply Voltage
SUPPLY VOLTAGE (V)
4
V
CM(LOWER LIMIT)
(V)
–2.0
–2.5
–3.0
–4.0
–5.0
–3.5
–4.5
–5.5
–6.0 4.754.25 5.25
1999 F03
5.54.5 5
BELOW GROUND INPUT
COMMON MODE RANGE
LIMITED BY V+
SUPPLY VOLTAGE
BELOW GROUND INPUT
COMMON MODE RANGE
LIMITED BY ESD CLAMPS
TYPICAL ESD CLAMP VOLTAGE
LT1999-10/LT1999-20/
LT1999-50
16
1999fd
For more information www.linear.com/LT1999
applicaTions inForMaTion
Shutdown Capability
If SHDN (Pin 8) is driven to within 0.5V of GND, the LT1999
is placed into a low power shutdown state in which the
part will draw aboutA from the V+ supply. The input
pins (+IN andIN) will draw approximately 1nA if biased
within the range of 0V to 80V (with no differential voltage
applied). If the input pins are pulled below the GND pin,
each input appears as a diode tied to GND in series with
approximately 4k of resistance. The REF pin appears as
approximately 0.4tied to a mid-supply potential. The
output appears as reverse biased diodes tied between the
output to either V+ or GND pins.
EMI Filtering and Layout Practices
An internal 1st order differential lowpass noise/EMI
suppression filter with a –3dB bandwidth of 10MHz (ap-
proximately 5× the LT1999’s –3dB bandwidth) is included
to help improve the LT1999’s EMI susceptibility and to
assist with the rejection of high frequency signals beyond
the bandwidth of the LT1999 that may introduce errors.
The pole is set by the following equation:
ffilt = 1/(π•(R+IN + RIN)•CF) ≈ 10MHz
Both the resistors and capacitors have a ±15% variation
so the pole can vary by approximately ±30% over manu-
facturing process and temperature variations.
The layout for lowest EMI/noise susceptibility is achieved
by keeping short direct connections and minimizing loop
areas (see Figure 4). If the user-supplied sense resistor
cannot be placed in close proximity to the LT1999, the
surface area of the loop comprising connections of +IN
to RSENSE and back toIN should be minimized. This
requires routing PCB traces connecting +IN to RSENSE
andIN to RSENSE adjacent with one another with minimal
separation. The metal traces connecting +IN to the sense
resistor andIN to the sense resistor should match and
use the same trace width.
Bypassing the V+ pin to the GND pin with a 0.1µF capacitor
with short wiring connection is recommended.
Figure 4. Recommended Layout
SUPPLY BYPASS
CAPACITOR
* KEEP LOOP AREA COMPRISING RSENSE, +IN AND –IN PINS
AS SMALL AS POSSIBLE.
** REF BYPASS TIED TO A LOW NOISE, LOW IMPEDANCE
SIGNAL GROUND PLANE.
OPTIONAL 10pF CAPACITOR TO PREVENT dV/dt EDGES
ON INPUT COUPLING TO FLOATING SHDN PIN.
**
*
FROM DC SOURCE
TO LOAD
RSENSE DIFFERENTIAL
ANALOG OUT
1999 F03
1
2
3
4
8
7
6
5
SHDN
OUT
REF
GND
V+
+IN
–IN
V+
LT1999-10/LT1999-20/
LT1999-50
17
1999fd
For more information www.linear.com/LT1999
applicaTions inForMaTion
The REF pin should be either driven by a low source im-
pedance (<100Ω) or should be bypassed with at least 1nF
to a low impedance, low noise, signal ground plane (see
Figure 4). Larger bypass capacitors on both V+ pins, and
the REF pin, will extend enhanced AC CMRR, and PSRR
performance to lower frequencies. Bypassing the REF pin
to a quiet ground plane filters the V+ pin or GND pin noise
that is sensed by the REF pin voltage divider and applied
to the noninverting input of output amplifier AO. Any com-
mon IR drops generated by pulsating ground currents in
common with the REF pin filter capacitor can compromise
the filtering performance and should be avoided.
If the SHDN pin is not driven and is left floating, routing
a PCB trace connecting Pins 1 and 8 under the part will
act as a shield, and will help limit edge coupling from the
inputs (Pins 2 and 3) to the SHDN pin. Periodic pulses on
the inputs with fast edges may glitch the high impedance
SHDN pin, periodically putting the part into low power
shutdown. Additional precaution against this may be taken
by adding an optional small (~10pF) capacitor may be tied
between V+ (Pin 1) and Pin 8.
Finally, when connecting the LT1999 inputs to the sense
resistor, it is important to use good Kelvin sensing prac-
tices (sensing the resistor in a way that excludes PCB trace
IR voltage drops). For sense resistors less than 1Ω, one
might consider using a 4-wire sense resistor to sense the
resistive element accurately.
Selection of the Current Sense Resistor
The external sense resistor selection presents a delicate
trade-off between power dissipation in the resistor and
current measurement accuracy.
In high current applications, the user may want to minimize
the power dissipated in the sense resistor. The sense re-
sistor current will create heat and voltage loss, degrading
efficiency. As a result, the sense resistor should be as
small as possible while still providing adequate dynamic
range required by the measurement. The dynamic range is
the ratio between the maximum accurately produced signal
generated by the voltage across the sense resistor, and
the minimum accurately reproduced signal. The minimum
accurately reproduced signal is primarily dictated by the
voltage offset of the LT1999. The maximum accurately
reproduced signal is dictated by the output swing of the
LT1999.
Thus the dynamic range for the LT1999 can be thought of
the maximum sense voltage divided by the input referred
voltage offset or:
Dynamic Range =
ΔV
OUT(MAX)
GAINV
OSI
The above equation tells us that the dynamic range is
inversely proportional to the gain of the LT1999. Thus,
if accuracy is of greater importance than efficiency or
power loss, the LT1999-10 used with the highest valued
sense resistor possible is recommended. If efficiency,
heat generated, and power loss in the resistive shunt is
the primary concern, the LT1999-50 and the lowest value
sense resistor possible is recommended. The LT1999-20
is available for applications somewhere in between these
two extremes.
LT1999-10/LT1999-20/
LT1999-50
18
1999fd
For more information www.linear.com/LT1999
applicaTions inForMaTion
Pinout Option Engineered for FMEA (Failure Mode and
Effects Analysis)
The LT1999 family of ICs is available with an 8-lead
MSOP pinout option engineered for FMEA (Failure Mode
and Effects Analysis): (LT1999-10F, LT1999-20F and the
LT1999-50F). See Figure 5 below.
The LT1999-XXF is designed to meet the most stringent
automotive requirements and to satisfactorily survive single
faults due to the most common PCB defects: 1) open pins
due to cold solder joints and 2) adjacent pin short circuits
due to adjacent pin solder bridging. The No-Connect Pin
(Pin 3) has been inserted between the input pin (–IN)
and the V+ supply pin to isolate the input voltages which
may range from –5V to 80V from solder bridging to the
V+ supply (typically 5V). Pin 3 is not connected internally
to the die and should be left unconnected.
The purpose of the FMEA is to emulate single faults and
determine whether or not they are destructive and/or
lead to conditions which could damage surrounding
components. The LT1999-XXF is configured as shown
in Figure2, with an input common mode of either 12V
or 0V. Each pin is systematically shorted to its adjacent
pin (emulating solder bridging) and the resulting effects
recorded. Each pin is then opened (emulating a cold solder
joint) with the resulting effects recorded.
In all instances, the LT1999-XXF recovers when these
fault conditions are removed. Furthermore, the output pin
(OUT) has been verified to never exceed the pin’s nominal
output range of 0V to 5V during fault testing.
Table 1 lists the behavior which results from shorting
adjacent pins and Table 2 details the behavior from open-
ing any pin.
SHDN
NC
V+
V+
V+
V+
2k
R+IN
R–IN
300Ω
CF
4pF
0.8k
0.8k
160k
160k
1999 F05a
2µA
OUT
REF
+IN
–IN
GND
+
+
G
RG
2k
2k
4.5k
2k
8
7
2
1
3
4
6
5
Figure 5. Simplified Block Diagram of the LT1999-XXF
LT1999-10/LT1999-20/
LT1999-50
19
1999fd
For more information www.linear.com/LT1999
applicaTions inForMaTion
Table 1: Behavior due to Adjacent Pin-to-Pin Shorts for the LT1999-10F, LT1999-20F, or the LT1999-50F
Adjacent Pin Short Test: (V+ = 5V, Tested at VCM = 0V, VCM = 12V, VCM = 80V)
PIN #
Adjacent Pins
Shorted
Recovery when
Fault is removed BEHAVIOR
1 – 2 +IN – –IN YES VOUT approaches the voltage on pin VREF.
2 – 3 –IN – NC YES The circuit behaves normally.
3 – 4 NC – V+ YES The circuit behaves normally.
5 – 6 GND – REF YES VOUT follows the voltage on Pin 6 or 0V.
6 – 7 REF – OUT YES VOUT approaches 5.0V
7 – 8 OUT – SHDN YES Supply Current drops by 5%.
Table 2: Behavior due to open pins for the LT1999-10F, LT1999-20F, or the LT1999-50F
Open Pin Test (V+ = 5V, Tested at VCM = 0V, VCM = 12V, VCM = 80V)
PIN # Pin Opened
Recovery when
Fault is removed BEHAVIOR
1 +IN YES VOUT may go to either V+ or GND, depending on the voltage applied to –IN. Generally, for –5V< –IN< 4V,
OUT will be near 5V. For –IN > 5V, OUT will be near 0V. In the range of 4V < –IN < 5V, OUT may go to either
V+ or GND, depending on the voltage applied to –IN. The open input (+IN) is biased internal to the IC to one
diode below V+.
2 –IN YES VOUT may go to either V+ or GND, depending on the voltage applied to +IN. Generally, for –5V < +IN < 4V,
OUT will be near 0V. For +IN > 5V, OUT will be at 5V. In the range of 4V < –IN < 5V, OUT may go to either
V+ or GND, depending on the voltage applied to +IN. The open input (–IN) is biased internal to the IC to one
diode below V+.
3 NC YES The circuit behaves normally.
4 V+YES The circuit will behave as if powered off.
5 GND YES OUT, REF will float up towards 3.9V.
6 REF YES The circuit behaves normally with more broadband noise on OUT.
7 OUT YES No VOUT signal.
8SHDN YES The low power shutdown feature will not function, otherwise the circuit behaves normally in the active state.
FMEA information in this document (not limited to, but including the description of behavior under specific pin-connection conditions) is provided for
convenience only. Ultimately, the end-user is responsible for verifying proper and reliable operation in each actual application. Linear Technology assumes
no liability whatsoever with providing this information.
LT1999-10/LT1999-20/
LT1999-50
20
1999fd
For more information www.linear.com/LT1999
applicaTions inForMaTion
VOUT
VREF
VSHDN
LT1999
4k
0.8k
160k
160k
2µA
0.8k
4k
SHDN
V+
V+
V+
+
+
8
1
2
3
4
7
6
5
RG
V+
V+
VS
5V
1999 F05
0.1µF
0.1µF
FUSE
STEERING
DIODE
LOAD
ILOAD
RSENSE
OFFON
5V
VOUT
V+IN
V–IN VREF
VSHDN
Figure 6. Using the LT1999 to Monitor a Fuse
Fuse Monitor
The inputs can be overdriven without fear of damaging
the LT1999. This makes the LT1999 ideal for monitoring
fuses if either +IN orIN are shorted to ground while the
other is at the full common mode supply voltage (see
Figure6). If the fuse in Figure6 opens with the +IN tied
to the positive supply, the load will pullIN to GND. The
output will be forced to the positive V+ supply rail. If it is
desired that the output be near ground if the fuse opens,
it is a simple matter of swapping the inputs. Precautions
should be followed: First, when the inputs are stressed
differentially due to the fuse blowing open, a large voltage
drop will be placed across the +IN toIN pins, dissipating
power in the precision on-chip input resistors. Precaution
should be taken to prevent junction temperatures from
exceeding the Absolute Maximum ratings (see Note 3 in the
Electrical Characteristics section). Secondly, if the load is
inductive, and the fuse blows open without a clamp diode,
energy stored in the inductive load will be dissipated in
the LT1999, which could cause damage. A simple steering
diode as shown in Figure6 will prevent this from happen-
ing, and will protect the LT1999 from damage.
Finally, the user should be aware that in fuse monitoring
applications with the sense voltage (VSENSE = V+INVIN)
being driven in excess of –25V, the output of the LT1999
will undergo phase reversal (see Figure7).
Figure 7. A Plot of the LT1999’s Output Voltage vs VSENSE (VSENSE = V+IN – VIN).
In Applications Where the Sense Voltage Is Driven in Excess of –25V, the
Output of the LT1999 Will Undergo Phase Reversal
VSENSE (V)
–60
VOUT (1V/DIV)
–30–45 –15 30
1999 F06
6015 450
VOUT PHASE REVERSAL FOR VSENSE < –25V
VREF = 2.5V
LT1999-10/LT1999-20/
LT1999-50
21
1999fd
For more information www.linear.com/LT1999
Typical applicaTions
Solenoid Current Monitor
The solenoid of Figure 8 consists of a coil of wire in an
iron case with permeable plunger that acts as a movable
element. When the MOSFET turns on, the diode is reversed
biased off, and current flows through RSENSE to actuate
the solenoid. If the MOSFET is turned off, the current
in the MOSFET is interrupted, but the energy stored in
the solenoid causes the diode to turn on and current to
freewheel in the loop consisting of the diode, RSENSE and
the solenoid.
Figure 8 shows the LT1999 monitoring currents in a
ground referenced solenoid used when the coil is hard
tied to the case, and is tied to ground. Figure 9 shows a
supply referenced solenoid whose coil is insulated from
the case. The LT1999 will interface equally well to either
of these two configurations.
Bidirectional PWM Motor Monitor
Pulse width modulation is commonly used to efficiently
vary the average voltage applied across a DC motor. The
H-bridge topology of Figure 10 allows full 4-quadrant
control: clockwise control, counter-clockwise control,
clockwise regeneration, and counter-clockwise regen-
eration. The LT1999 in conjunction with a non-inductive
current shunt is used to monitor currents in the rotor.
The LT1999 can be used to detect stuck rotors, provide
detection of overcurrent conditions in general, or provide
current mode feedback control.
Figure 11 shows a plot of the output voltage of the LT1999.
Figure 8. Solenoid Current Monitor for Ground Tied Solenoid. The Common Mode
Inputs to the LT1999 Switch Between VS and One Diode Drop Below Ground
LT1999
4k
0.8k
160k
160k
2µA
0.8k
4k
SHDN
V+
V+
V+
+
+
8
1
2
3
4
7
6
5
RG
V+
V+
TIME (50ms/DIV)
VOUT (0.5V/DIV)
V+IN (10V/DIV)
5V
VS
5V
1999 F07a
1999 F07b
0.1µF
0.1µF
SOLENOID
RSENSE
V+IN
VSHDN
VOUT
VREF
V–IN
ON
OFF
VOUT
V+IN
SOLENOID PLUNGER PULLS IN
SOLENOID RELEASES
2.5V
LT1999-10/LT1999-20/
LT1999-50
22
1999fd
For more information www.linear.com/LT1999
Figure 9. Solenoid Current Monitor for Non-Grounded Solenoids. This Circuit Performs the
Same Function as Figure 7 Except One End of the Solenoid Is Tied to VS. The Common Mode
Voltage of Inputs of the LT1999 Switch Between Ground and One Diode Drop Above VS
Typical applicaTions
LT1999
4k
0.8k
160k
160k
2µA
0.8k
4k
SHDN
V+
+
+
8
2
3
7
6
5
RG
V+
V+
5V
VS
5V
1999 F08a
1
40.1µF
2.5V
0.1µF
SOLENOID
RSENSE
VOUT
VREF
VSHDN
ON
OFF V+
V+
V+IN
V–IN
TIME (50ms/DIV)
VOUT (0.5V/DIV)
V+IN (10V/DIV)
VOUT
V+IN
SOLENOID PLUNGER PULLS IN
SOLENOID RELEASES
1999 F08b
LT1999-10/LT1999-20/
LT1999-50
23
1999fd
For more information www.linear.com/LT1999
Typical applicaTions
Figure 10. Armature Current Monitor for DC Motor Applications
Figure 11. LT1999 Output Waveforms for the Circuit of Figure 10
1999 F09
VBRIDGE
V+IN
V–IN
RSENSE
0.025
10µF
PWM INPUT
DIRECTION
BRAKE INPUT
24V
5V
5V
GND
5V
PWM IN OUTA
OUTB
C4
1000µF
24V MOTOR
H-BRIDGE
LT1999-20
4k
0.8k
160k
160k
2µA
0.8k
4k
SHDN
+
+
80k
V+
V+
V+
V+0.1µF
0.1µF
8
7
6
VSHDN
VOUT
VREF
2
3
1
4
V+
5
TIME (20µs/DIV)
VOUT (2V/DIV)
V+IN (20V/DIV)
1999 F10
VOUT
V+IN
2.5V
LT1999-10/LT1999-20/
LT1999-50
24
1999fd
For more information www.linear.com/LT1999
package DescripTion
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MSOP (MS8) 0213 REV G
0.53 ±0.152
(.021 ±.006)
SEATING
PLANE
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.18
(.007)
0.254
(.010)
1.10
(.043)
MAX
0.22 – 0.38
(.009 – .015)
TYP
0.1016 ±0.0508
(.004 ±.002)
0.86
(.034)
REF
0.65
(.0256)
BSC
0° – 6° TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
1 2 34
4.90 ±0.152
(.193 ±.006)
8765
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
0.52
(.0205)
REF
5.10
(.201)
MIN
3.20 – 3.45
(.126 – .136)
0.889 ±0.127
(.035 ±.005)
RECOMMENDED SOLDER PAD LAYOUT
0.42 ± 0.038
(.0165 ±.0015)
TYP
0.65
(.0256)
BSC
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660 Rev G)
.016 – .050
(0.406 – 1.270)
.010 – .020
(0.254 – 0.508)× 45°
0°– 8° TYP
.008 – .010
(0.203 – 0.254)
SO8 REV G 0212
.053 – .069
(1.346 1.752)
.014 – .019
(0.355 – 0.483)
TYP
.004 – .010
(0.101 0.254)
.050
(1.270)
BSC
1234
.150 – .157
(3.810 – 3.988)
NOTE 3
8765
.189 – .197
(4.801 – 5.004)
NOTE 3
.228 – .244
(5.791 – 6.197)
.245
MIN .160 ±.005
RECOMMENDED SOLDER PAD LAYOUT
.045 ±.005
.050 BSC
.030 ±.005
TYP
INCHES
(MILLIMETERS)
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610 Rev G)
LT1999-10/LT1999-20/
LT1999-50
25
1999fd
For more information www.linear.com/LT1999
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
revision hisTory
REV DATE DESCRIPTION PAGE NUMBER
A 5/11 Revised +IN and –IN pin descriptions in Pin Functions section 12
B 3/12 Revised Voltage Output Swing Low specification (VOUT) under a loaded condition of 1kΩ to mid-supply.
Updated Figure 4 to multicolor.
4, 6
16
C 2/15 Addition of MSOP Pinout Option Engineered for FMEA
Correction to AV Specification for LT1999-50 from 48.75 to 49.75
Update to Pin Functions to include Pinout Option Engineered for FMEA
Addition of New Application Information "Pinout Option Engineered for FMEA"
Addition of Figure 5 and Renumbering of Figures 6 to 11
Addition of Table 1 and Table 2
All
5
12
18, 19
18 to 23
19
D 6/15 LT1999F added to Figure 1 (Simplified Block Diagram)
LT1999F added to Figure 2 (Test Circuit)
Additional test condition (VCM = 80) added to table 1 and table 2
Note added regarding the use of FMEA information
13
14
19
19
LT1999-10/LT1999-20/
LT1999-50
26
1999fd
For more information www.linear.com/LT1999
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 l FAX: (408) 434-0507 l www.linear.com
LINEAR TECHNOLOGY CORPORATION 2010
LT 0615 REV D • PRINTED IN USA
Typical applicaTion
PART NUMBER DESCRIPTION COMMENTS
LT1787/
LT1787HV
Precision, Bidirectional High Side Current Sense Amplifier 2.7V to 60V Operation, 75μV Offset, 60μA Current Draw
LT6100 Gain-Selectable High Side Current Sense Amplifier 4.1V to 48V Operation, Pin-Selectable Gain:
10V/V, 12.5V/V, 20V/V, 25V/V, 40V/V, 50V/V
LTC6101/
LTC6101HV
High Voltage High Side Current Sense Amplifier 4V to 60V/5V to 100V Operation, External Resistor Set Gain, SOT23
LTC6102/
LTC6102HV
Zero Drift High Side Current Sense Amplifier 4V to 60V/5V to 100V Operation, ±10μV Offset, 1μs Step Response,
MSOP8/DFN Packages
LTC6103 Dual High Side Precision Current Sense Amplifier 4V to 60V, Gain Configurable, 8-Pin MSOP Package
LTC6104 Bidirectional, High Side Current Sense 4V to 60V, Gain Configurable, 8-Pin MSOP Package
LT6106 Low Cost, High Side Precision Current Sense Amplifier 2.7V to 36V, Gain Configurable, SOT23 Package
LT6105 Precision, Extended Input Range Current Sense Amplifier –0.3 to 44V, Gain Configurable, 8-Pin MSOP Package
LTC4150 Coulomb Counter/Battery Gas Gauge Indicates Charge Quantity and Polarity
LT1990 Precision, 100μA Gain Selectable Amplifier 2.7V to 36V Operation, CMRR > 70dB, Input Voltage = ±250V
LT1991 ±250V Input Range Difference Amplifier 2.7V to 36V Operation, 50μV Offset, CMRR > 75B, Input Voltage = ±60V
LT1637/LT1638 1.1/1.2MHz, 0.4V/μs Over-The-Top, Rail-to-Rail Input and
Output Amplifier
0.4V/μs Slew Rate, 230μA per Amplifier
relaTeD parTs
1999 TA02
5V 0.1µF
LT1999-10
4k
0.8k
160k
160k
2µA
0.8k
4k
V+
+
SHDN
+
VOUT
40k
VREF
VSHDN
V+
V+
V+
V+
4
0.1µF
5V
CHARGER
LOAD
0.025Ω
BAT
42V
VCC VREF
0.1µF
+IN
10µF
CS
SCK
SDO
LTC2433-1VOUT
+
5V
–IN
0.1µF
2
3
1
5
7
6
8
V+IN
V–IN
Battery Charge Current and Load Current Monitor
VOUT = 0.25V/A, Maximum Measured Current ±9.5A
(408) 432-1900 l FAX: (408) 434-0507 l www.linear.com/LT1999

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