LT6107 Datasheet by Analog Devices Inc.

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D ANALOG DEVICES LT61 O7
LT6107
1
6107fc
For more information www.linear.com/LT6107
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
High Temperature High Side
Current Sense Amp in SOT-23
The LT
®
6107 is a versatile high side current sense ampli-
fier designed for operation over a wide temperature range.
Design flexibility is provided by the excellent device char-
acteristics: 250µV maximum offset and 40nA maximum
input bias current. Gain for each device is set by two
resistors and allows for accuracy better than 1%.
The LT6107 monitors current via the voltage across an
external sense resistor (shunt resistor). Internal circuitry
converts input voltage to output current, allowing for a
small sense signal on a high common mode voltage to
be translated into a ground referenced signal. The low DC
offset allows for monitoring very small sense voltages. As
a result, a small valued shunt resistor can be used, which
minimizes the power loss in the shunt.
The wide 2.7V to 44V input voltage range, high accuracy
and wide operating temperature range make the LT6107
ideal for automotive, industrial and power management
applications. The very low power supply current of the
LT6107 also makes it suitable for low power and battery
operated applications. For applications not requiring the
wide temperature range, see the LT6106.
n Fully Tested at –55°C (MP), –40°C (H),
25°Cand150°C
n Gain Configurable with Two Resistors
n Low Offset Voltage: 250µV Maximum
n Output Current: 1mA Maximum
n Supply Range: 2.7V to 36V, 44V Absolute Maximum
n Low Input Bias Current: 40nA Maximum
n PSRR: 106dB Minimum
n Low Supply Current: 65µA Typical, V+ = 12V
n Low Profile (1mm) ThinSOT
TM
Package
n Current Shunt Measurement
n Battery Monitoring
n Power Management
n Motor Control
n Lamp Monitoring
n Overcurrent and Fault Detection
LT6107
1k
VOUT
200mV/A
6107 TA01a
100Ω
3V TO 36V
LOAD
0.02Ω
+
V+
V
OUT
–IN+IN
3V to 36V, 5A Current Sense with AV = 10 Measurement Accuracy vs Load Current
LOAD CURRENT (A)
0
–1.2
ACCURACY (% OF FULL SCALE)
–1.0
–0.6
–0.4
–0.2
245
0.6
6107 TA01b
–0.8
1 3
0
0.2
0.4
TYPICAL PART, TA = 25°C
5A FULL SCALE
RSENSE = 0.02
AV = 10
RIN = 100
ROUT = 1k
V+ = 3V
All registered trademarks and trademarks are the property of their respective owners.
LTéI O7 I: :I I: I: :I 55 PACKAGE srLEAD PLASTIC T501723
LT6107
2
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PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS
Supply Voltage (V+ to V) ..........................................44V
Input Voltage (+IN to V) ............................................. V+
(–IN to V) ............................................ V+
Input Current ........................................................10mA
Output Short-Circuit Duration .......................... Indefinite
Operating Temperature Range (Note 2)
LT6107H ............................................ 40°C to 150°C
LT6107MP.......................................... –55°C to 150°C
Specified Temperature Range (Note 2)
LT6107H ............................................ 40°C to 150°C
LT6107MP.......................................... –55°C to 150°C
Storage Temperature Range .................. 65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................... 300°C
(Note 1)
OUT 1
V 2
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
–IN 3
5 V+
4 +IN
TJMAX = 150°C, JA = 250°C/W
ORDER INFORMATION
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V+Supply Voltage Range l2.7 36 V
VOS Input Offset Voltage VSENSE = 5mV
l
150 250
400
µV
µV
∆VOS/∆T Input Offset Voltage Drift VSENSE = 5mV l1µV/°C
IBInput Bias Current (+IN) V+ = 12V, 36V
l
40
65
nA
nA
IOS Input Offset Current V+ = 12V, 36V 1 nA
IOUT Maximum Output Current (Note 3) l1 mA
PSRR Power Supply Rejection Ratio V+ = 2.7V to 36V, VSENSE = 5mV l106 dB
VSENSE(MAX) Input Sense Voltage Full Scale RIN = 500Ω (Notes 3, 7) l0.5 V
AV Error Gain Error (Note 4) VSENSE = 500mV, RIN = 500Ω, ROUT = 10k, V+ = 12.5V l–0.65 –0.25 0 %
VSENSE = 500mV, RIN = 500Ω, ROUT = 10k, V+ = 36V l–0.45 –0.14 0.1 %
The l denotes the specifications which apply over the full specified
operating temperature range, otherwise specifications are at TA = 25°C. V+ = 12V, V+ = VSENSE+, RIN = 100Ω, ROUT = 10k, Gain = 100
unless otherwise noted. (Note 6)
Lead Free Finish
TAPE AND REEL (MINI) TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT6107HS5#TRMPBF LT6107HS5#TRPBF LTDGZ 5-Lead Plastic TSOT-23 –40°C to 150°C
LT6107MPS5#TRMPBF LT6107MPS5#TRPBF LTDGZ 5-Lead Plastic TSOT-23 –55°C to 150°C
Lead Based Finish
TAPE AND REEL (MINI) TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT6107MPS5#TRM LT6107MPS5#TR LTDGZ 5-Lead Plastic TSOT-23 –55°C to 150°C
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
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/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
http://www.linear.com/product/LT6107#orderinfo
LT6107
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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. In addition to the Absolute Maximum Ratings, the
output current of the LT6107 must be limited to insure that the power
dissipation in the LT6107 does not allow the die temperature to exceed
150°C. See the applications information section “Power Dissipation
Considerations” for further information.
Note 2: Junction temperatures greater than 125°C will promote
accelerated aging. The LT6107 has demonstrated typical life beyond 1000
hours at 150°C. LT6107H is guaranteed to meet specified performance
from –40°C to 150°C. LT6107MP is guaranteed to meet specified
performance from –55°C to 150°C.
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full specified
operating temperature range, otherwise specifications are at TA = 25°C. V+ = 12V, V+ = VSENSE+, RIN = 100Ω, ROUT = 10k, Gain = 100
unless otherwise noted. (Note 6)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VOUT(HIGH) Output Swing High
(Referred to V+)
VSENSE = 120mV
l
1.2
1.4
V
V
Minimum Output Voltage
(Note 5)
VSENSE = 0mV, RIN = 100Ω, ROUT = 10k
l
12 45
85
mV
mV
VSENSE = 0mV, RIN = 500Ω, ROUT = 10k, V+ = 12V, 36V
l
7 16
40
mV
mV
BW Signal Bandwidth (–3dB) IOUT = 1mA, RIN = 100Ω, ROUT = 5k 200 kHz
trInput Step Response (to 50% of
Output Step)
∆VSENSE = 100mV Step, RIN = 100Ω, ROUT = 5k,
Rising Edge
3.5 µs
ISSupply Current V+ = 2.7V, IOUT = 0µA, (VSENSE = –5mV)
l
60 85
120
µA
V+ = 12V, IOUT = 0µA, (VSENSE = –5mV)
l
65 95
125
µA
V+ = 36V, IOUT = 0µA, (VSENSE = –5mV)
l
70 100
135
µA
Note 3: Guaranteed by the gain error test.
Note 4: Gain error refers to the contribution of the LT6107 internal circuitry
and does not include errors in the external gain setting resistors.
Note 5: The LT6107 output is an open collector current source. The
minimum output voltage scales directly with the ratio ROUT/10k.
Note 6: VSENSE+ is the voltage at the high side of the sense resistor,
RSENSE. See Figure 1.
Note 7: VSENSE(MAX) is the maximum sense voltage for which the Electrical
Characteristics will apply. Higher voltages can affect performance but will
not damage the part provided that the output current of the LT6107 does
not exceed the allowable power dissipation as described in Note 1.
TYPICAL PERFORMANCE CHARACTERISTICS
Input Offset Voltage vs
Temperature
INPUT OFFSET VOLTAGE (µV)
–200
PERCENT OF UNITS (%)
10
12
16
120
6107 G23
4
8
14
6
2
0–120 –40 0 40 200
V
+
= 12V
VSENSE = 5mV
RIN = 100Ω
ROUT = 10k
1068 UNITS
VOS Distribution
SUPPLY VOLTAGE (V)
0
CHANGE IN INPUT OFFSET VOLTAGE (µV)
10
40
50
40
6107 G02
0
–10
–70 10 20 30
515 25 35
–30
70
60
30
20
–20
–40
–50
–60
VSENSE = 5mV
RIN = 100Ω
ROUT = 10k
TYPICAL UNITS
Input Offset Voltage vs
Supply Voltage
TEMPERATURE (°C)
–55 –35 –15 525 45 65 85 105 125 145 165
–300
–400
INPUT OFFSET VOLTAGE (µV)
–200
0
100
200
600
6107 G03
–100
300
400
500
VSENSE = 5mV
V+ = 12V
RIN = 100Ω
ROUT = 10k
AV = 100
TYPICAL UNITS
LT6107
LT6107
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TYPICAL PERFORMANCE CHARACTERISTICS
Gain vs Frequency
Step Response 0mV to 10mV
(RIN = 100Ω)
Step Response 10mV to 20mV
(RIN = 100Ω)
Gain vs Frequency
Input Bias Current vs Supply
Voltage
Power Supply Rejection Ratio
vs Frequency
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
SUPPLY VOLTAGE (V)
0
INPUT BIAS CURRENT (nA)
40
6107 G05
105 2015 30 35 45
25 50
VSENSE = 5mV
RIN = 100Ω
TA = –55°C
TA = –40°C
TA = 25°C
TA = 70°C
TA = 125°C
TA = 150°C
TA = 175°C
FREQUENCY (Hz)
20
40
60
80
100
100 10k 100k
6107 G06
0
1k
10
30
50
70
90
110
VOUT = 2.5V
VOUT = 5V
VOUT = 10V
V+ = 12.5V
AV = 20
RIN = 500Ω
ROUT = 10k
Power Supply Rejection Ratio
vs Frequency
FREQUENCY (Hz)
20
POWER SUPPLY REJECTION RATIO (dB)
40
60
80
100
100 10k 100k
1M
6107 G08
0
1k
120
10
30
50
70
90
110
VOUT = 0.5V
VOUT = 1V
VOUT = 2V
V+ = 12.5V
AV = 20
RIN = 100Ω
ROUT = 2k
FREQUENCY (Hz)
10
GAIN (dB)
40
45
5
0
35
20
30
25
15
1k 100k 1M 10M
6107 G09
–30
–25
–20
–15
–10
–5
10k
V+ = 12.5V
AV = 100
RIN = 100Ω
ROUT = 10k
VOUT = 10V
VOUT = 2.5V
VSENSE
20mV/DIV
VOUT
500mV/DIV
0V
5µs/DIVAV = 100
VOUT = 0V TO 1V
ROUT = 10k
V
+
= 12V
6107 G10
VSENSE
20mV/DIV
VOUT
500mV/DIV
0V
5µs/DIVAV = 100
VOUT = 1V TO 2V
ROUT = 10k
V
+
= 12V
6107 G11
FREQUENCY (Hz)
10
GAIN (dB)
40
45
5
0
35
20
30
25
15
1k 100k 1M 10M
6107 G14
–30
–25
–20
–15
–10
–5
10k
V+ = 12.5V
AV = 20
RIN = 500Ω
ROUT = 10k
VOUT = 10V
VOUT = 2.5V
Gain Error vs Temperature
Gain Error Distribution
GAIN ERROR (%)
–0.60
0
PERCENT OF UNITS (%)
4
2
8
6
10
24
20
–0.48 –0.36
22
18
16
14
12
–0.24 –0.12
0
6107 G24
V+ = 12.5V
VSENSE = 500mV
RIN = 500Ω
ROUT = 10k
11,072 UNITS
TA = 25°C
TEMPERATURE (°C)
60
GAIN ERROR (%)
–0.20
–0.10
120 140 180160
6107 G04
–0.30
–0.40
–0.45 0 40 80
40 20 20 60 100
0.00
–0.25
–0.15
–0.35
–0.05
VOUT = 1V
IOUT = 1mA
ROUT = 1k
V+ = 36V
V+ = 12V
V+ = 5V
V+ = 2.7V
LT6107 saw. mm nuns Sun x. on m: v- an new null" s»-
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Output Voltage Swing vs
Temperature
Step Response 0mV to 100mV
(RIN = 100Ω)
TYPICAL PERFORMANCE CHARACTERISTICS
Step Response 0mV to 50mV
(RIN = 500Ω)
Step Response 50mV to 500mV
(RIN = 500Ω)
Output Voltage vs Input Sense
Voltage (0mV ≤ VSENSE ≤ 10mV)
Step Response 10mV to 100mV
(RIN = 100Ω)
Step Response 50mV to 100mV
(RIN = 500Ω)
–60 –20 0 40 80 160 180140–40 20 60 120100
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
11.00
11.05
11.15
11.10
6107 G07
10.95
10.90
10.85
10.80
V+ = 12V
AV = 100
RIN = 100Ω
ROUT = 10k
VSENSE = 120mV
VSENSE
200mV/DIV
VOUT
2V/DIV
0V
5µs/DIVAV = 100
VOUT = 0V TO 10V
ROUT = 10k
V
+
= 12V
6107 G12
VSENSE
200mV/DIV
VOUT
2V/DIV
0V
5µs/DIVAV = 100
VOUT = 1V TO 10V
ROUT = 10k
V
+
= 12V
6107 G13
VSENSE
100mV/DIV
VOUT
500mV/DIV
0V
5µs/DIVAV = 20
VOUT = 1V TO 2V
ROUT = 10k
V
+
= 12V
6107 G15
VSENSE
100mV/DIV
VOUT
500mV/DIV
0V
5µs/DIVAV = 20
VOUT = 0V TO 1V
ROUT = 10k
V
+
= 12V
6107 G16
VSENSE
1V/DIV
VOUT
2V/DIV
0V
5µs/DIVAV = 20
VOUT = 1V TO 10V
ROUT = 10k
V
+
= 12V
6107 G17
Step Response 0mV to 500mV
(RIN = 500Ω)
VSENSE
1V/DIV
VOUT
2V/DIV
0V
5µs/DIVAV = 20
VOUT = 0V TO 10V
ROUT = 10k
V
+
= 12V
6107 G18
VSENSE (mV)
0
VOUT (mV)
600
800
1100
1000
8 9
6107 G19
400
200
500
700
900
300
100
0246
135710
V+ = 12V
AV = 100
RIN = 100Ω
ROUT = 10k
Output Voltage vs Input Sense
Voltage (0mV ≤ VSENSE ≤ 10mV)
VSENSE (mV)
0
VOUT (mV)
120
160
220
200
8 9
6107 G20
80
40
100
140
180
60
20
0246
135710
V+ = 12V
AV = 20
RIN = 500Ω
ROUT = 10k
LT6107
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BLOCK DIAGRAM
PIN FUNCTIONS
OUT (Pin 1):
Current Output. OUT will source a current
that is proportional to the sense voltage into an external
resistor.
V (Pin 2):
Normally Connected to Ground.
IN (Pin 3):
The internal sense amplifier will drive –IN to
the same potential as +IN. A resistor (RIN) tied from V+
to –IN
sets the output current IOUT
= VSENSE/RIN. VSENSE
is the voltage developed across RSENSE.
+IN (Pin 4):
Must be tied to the system load end of the
sense resistor, either directly or through a resistor.
V+ (Pin 5):
Positive Supply Pin. The V+ pin should be con-
nected directly to either side of the sense resistor, RSENSE.
Supply current is drawn through this pin. The circuit may
be configured so that the LT6107 supply current is or
is not monitored along with the system load current. To
monitor only the system load current, connect
V+
to the
more positive side of the sense resistor. To monitor the
total current, including that of the LT6107, connect
V+
to
the more negative side of the sense resistor.
+
V+
VOUT
6107 F01
VBATTERY
IOUT
VSENSE
RSENSE
ILOAD
ROUT
+
L
O
A
D
VOUT = VSENSE ROUT
RIN
14k
14k
–IN
+IN
5
2
1
3
4
RIN
Figure 1. LT6107 Block Diagram and Typical Connection
TYPICAL PERFORMANCE CHARACTERISTICS
VSENSE (mV)
0
V
OUT
(V)
4
8
12
2
6
10
40 80 120 160
6107 G21
200200 60 100 140 180
V+ = 12V
AV = 100
RIN = 100Ω
ROUT = 10k
VSENSE (mV)
0
V
OUT
(V)
4
8
12
2
6
10
200 400 600 800
6107 G22
10001000 300 500 700 900
V+ = 12V
AV = 20
RIN = 500Ω
ROUT = 10k
Supply Current vs Supply Voltage
SUPPLY VOLTAGE (V)
0
0
SUPPLY CURRENT (µA)
20
60
80
100
10 20 25 45
6107 G01
40
5 15 30 35 40
120
TA = –55°C
TA = –40°C
TA = 25°C
TA = 70°C
TA = 125°C
TA = 150°C
TA = 175°C
Output Voltage vs Input Sense
Voltage (0mV ≤ VSENSE ≤ 1V)
Output Voltage vs Input Sense
Voltage (0mV ≤ VSENSE ≤ 200mV)
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APPLICATIONS INFORMATION
Introduction
The LT6107 high side current sense amplifier (Figure 1) pro-
vides accurate monitoring of current through a user-selected
sense resistor. The sense voltage is amplified by a user-
selected gain and level shifted from the positive power sup-
ply to a ground-referred output. The output signal is analog
and may be used as is, or processed with an output filter.
Theory of Operation
An internal sense amplifier loop forces –IN to have the
same potential as +IN. Connecting an external resistor,
RIN, between IN and V+ forces a potential across RIN
that is the same as the sense voltage across RSENSE. A
corresponding current, V
SENSE
/R
IN
, will flow through R
IN
.
The high impedance inputs of the sense amplifier will not
conduct this current, so it will flow through an internal
PNP to the output pin as IOUT.
The output current can be transformed into a voltage by
adding a resistor from OUT to V. The output voltage is
then VO = V
+ IOUT • ROUT.
Table 1. Useful Gain Configurations
GAIN RIN ROUT VSENSE at VOUT = 5V IOUT at VOUT = 5V
20 499Ω 10k 250mV 500µA
50 200Ω 10k 100mV 500µA
100 100Ω 10k 50mV 500µA
GAIN RIN ROUT VSENSE at VOUT = 2.5V IOUT at VOUT = 2.5V
20 249Ω 5k 125mV 500µA
50 100Ω 5k 50mV 500µA
100 50Ω 5k 25mV 500µA
Selection of External Current Sense Resistor
The external sense resistor, RSENSE, has a significant
effect on the function of a current sensing system and
must be chosen with care.
First, the power dissipation in the resistor should be con-
sidered. The system load current will cause both heat and
voltage loss in RSENSE. As a result, the sense resistor
should be as small as possible while still providing the
input dynamic range required by the measurement. Note
that input dynamic range is the difference between the
maximum input signal and the minimum accurately mea-
sured signal, and is limited primarily by input DC offset of
the internal amplifier of the LT6107. In addition, RSENSE
must be small enough that VSENSE does not exceed the
maximum input voltage specified by the LT6107, even
under peak load conditions. As an example, an application
may require that the maximum sense voltage be 100mV.
If this application is expected to draw 2A at peak load,
RSENSE should be no more than 50mΩ.
Once the maximum RSENSE value is determined, the min-
imum sense resistor value will be set by the resolution or
dynamic range required. The minimum signal that can be
accurately represented by this sense amplifier is limited
by the input offset. As an example, the LT6107 has a typi-
cal input offset of 150µV. If the minimum current is 20mA,
a sense resistor of 7.5mΩ will set VSENSE to 150µV. This
is the same value as the input offset. A larger sense resis-
tor will reduce the error due to offset by increasing the
sense voltage for a given load current. Choosing a 50mΩ
RSENSE will maximize the dynamic range and provide a
system that has 100mV across the sense resistor at peak
load (2A), while input offset causes an error equivalent
to only 3mA of load current. Peak dissipation is 200mW.
If a 5mΩ sense resistor is employed, then the effective
current error is 30mA, while the peak sense voltage is
reduced to 10mV at 2A, dissipating only 20mW.
The low offset and corresponding large dynamic range
of the LT6107 make it more flexible than other solutions
in this respect. The 150µV typical offset gives 60dB
of dynamic range for a sense voltage that is limited to
150mV maximum, and over 70dB of dynamic range if the
rated input maximum of 0.5V is allowed.
Sense Resistor Connection
Kelvin connection of the –IN and +IN inputs to the sense
resistor should be used in all but the lowest power appli-
cations. Solder connections and PC board interconnec-
tions that carry high current can cause significant error
in measurement due to their relatively large resistances.
One 10mm × 10mm square trace of one-ounce copper
is approximately 0.5mΩ. A 1mV error can be caused by
as little as 2A flowing through this small interconnect.
This will cause a 1% error in a 100mV signal. A 10A load
current in the same interconnect will cause a 5% error
for the same 100mV signal. By isolating the sense traces
from the high current paths, this error can be reduced
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APPLICATIONS INFORMATION
by orders of magnitude. A sense resistor with integrated
Kelvin sense terminals will give the best results. Figure 2
illustrates the recommended method.
This approach can be helpful in cases where occasional
bursts of high currents can be ignored.
Care should be taken when designing the board layout for
RIN, especially for small RIN values. All trace and inter-
connect resistances will increase the effective RIN value,
causing a gain error.
Selection of External Output Resistor, ROUT
The output resistor, ROUT, determines how the output cur-
rent is converted to voltage. VOUT is simply IOUT • ROUT.
In choosing an output resistor, the maximum output
voltage must first be considered. If the following circuit
is a buffer or ADC with limited input range, then R
OUT
must be chosen so that IOUT(MAX) ROUT is less than the
allowed maximum input range of this circuit.
In addition, the output impedance is determined by R
OUT
. If
the circuit to be driven has high enough input impedance,
then almost any useful output impedance will be accept-
able. However, if the driven circuit has relatively low input
impedance, or draws spikes of current such as an ADC
might do, then a lower R
OUT
value may be required in order
to preserve the accuracy of the output. As an example, if
the input impedance of the driven circuit is 100 times R
OUT
,
then the accuracy of VOUT will be reduced by 1% since:
VOUT IOUT ROUT • RIN(DRIVEN)
ROUT RIN(DRIVEN)
IOUT • ROUT 100
101 0.99 • IOUT • ROUT
Error Sources
The current sense system uses an amplifier and resistors
to apply gain and level shift the result. The output is then
dependent on the characteristics of the amplifier, such as
gain and input offset, as well as resistor matching.
Ideally, the circuit output is:
VOUT VSENSE ROUT
R
IN
; VSENSE RSENSE • ISENSE
In this case, the only error is due to resistor mismatch,
which provides an error in gain only. However, offset
voltage and bias current cause additional errors.
Figure 3. Shunt Diode Limits Maximum Input Voltage to Allow
Better Low Input Resolution Without Overranging
Figure 2. Kelvin Input Connection Preserves Accuracy with
Large Load Currents
Selection of External Input Resistor, RIN
R
IN
should be chosen to allow the required resolution
while limiting the output current to 1mA. In addition, the
maximum value for RIN is 500Ω. By setting RIN such that
the largest expected sense voltage gives I
OUT
= 1mA, then
the maximum output dynamic range is available. Output
dynamic range is limited by both the maximum allowed
output current and the maximum allowed output voltage,
as well as the minimum practical output signal. If less
dynamic range is required, then RIN can be increased
accordingly, reducing the maximum output current and
power dissipation. If low sense currents must be resolved
accurately in a system that has a very wide dynamic range,
a smaller RIN than the maximum current spec allows may
be used if the maximum current is limited in another way,
such as with a Schottky diode across RSENSE (Figure 3).
This will reduce the high current measurement accuracy
by limiting the result, while increasing the low current
measurement resolution.
LT6107
ROUT
VOUT
6107 F02
RIN
V+
LOAD
RSENSE
+
V+
V
OUT
–IN+IN
V
+
LOAD
DSENSE
6107 F03
RSENSE
LT6107 M w I I SENSE
LT6107
9
6107fc
For more information www.linear.com/LT6107
APPLICATIONS INFORMATION
Output Error Due to the Amplifier DC Offset
Voltage, VOS
EOUT(VOS) VOS ROUT
R
IN
The DC offset voltage of the amplifier adds directly to the
value of the sense voltage, VSENSE. This is the dominant
error of the system and it limits the low end of the dynamic
range. The paragraph Selection of External Current Sense
Resistor” provides details.
Output Error Due to the Bias Currents, IB+ and IB
The bias current IB+ flows into the positive input of the
internal op amp. IB flows into the negative input.
EOUT(IBIAS) ROUT IBRSENSE
RIN
– IB
Assuming IB+ IB = IBIAS, and RSENSE << RIN then:
EOUT(IBIAS)
–ROUT • IBIAS
It is convenient to refer the error to the input:
EIN(IBIAS)
–RIN • IBIAS
For instance if IBIAS is 60nA and RIN is 1k, the input referred
error is 60µV. Note that in applications where RSENSE
RIN, IB+ causes a voltage offset in RSENSE that cancels the
error due to IB and EOUT(IBIAS)
0mV. In most applica-
tions, RSENSE << RIN, the bias current error can be similarly
reduced if an external resistor R
IN+
= (R
IN
R
SENSE
) is
connected as shown in Figure 4. Under both conditions:
EIN(IBIAS)
= ±RIN • IOS; where IOS
= IB+ – IB
If the offset current, IOS, of the LT6107 amplifier is 6nA,
the 60µV error above is reduced to 6µV.
Adding RIN+
as described will maximize the dynamic
range of the circuit. For less sensitive designs, R
IN+
is
not necessary.
Output Error Due to Gain Error
The LT6107 exhibits a typical gain error of –0.25% at 1mA
output current. The primary source of gain error is due to
the finite gain to the PNP output transistor, which results
in a small percentage of the current in RIN not appearing in
the output load ROUT.
Minimum Output Voltage
The curves of the Output Voltage vs Input Sense Voltage
show the behavior of the LT6107 with low input sense
voltages. When VSENSE = 0V, the output voltage will always
be slightly positive, the result of input offset voltages and
of a small amount of quiescent current (0.7µA to 1.2µA)
flowing through the output device. The minimum output
voltage in the Electrical Characteristics table include both
these effects.
Power Dissipation Considerations
The power dissipated by the LT6107 will cause a small
increase in the die temperature. This rise in junction tem-
perature can be calculated if the output current and the
supply current are known.
The power dissipated in the LT6107 due to the output
signal is:
POUT = (V–IN – VOUT) • IOUT
Since V–IN V+, POUT (V+ – VOUT) • IOUT
The power dissipated due to the quiescent supply current is:
PQ = IS • (V+ – V)
The total power dissipated is the output dissipation plus
the quiescent dissipation:
PTOTAL = POUT + PQ
The junction temperature is given by:
TJ = TA + JA • PTOTAL
At the maximum operating supply voltage of 36V and the
maximum guaranteed output current of 1mA, the total
Figure 4. Second Input R Minimizes Error Due to Input Bias Current
LT6107
ROUT
VOUT
6107 F04
RIN
RIN+
V
+
LOAD
RSENSE
+
V+
V
OUT
RIN+ = RIN – RSENSE
–IN+IN
LT6107 V0 UT OUT OUT SENSE OUT VOUT OUT ‘IO
LT6107
10
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For more information www.linear.com/LT6107
APPLICATIONS INFORMATION
power dissipation is 41mW. This amount of power dis-
sipation will result in a 10°C rise in junction temperature
above the ambient temperature.
It is important to note that the LT6107 has been designed
to provide at least 1mA to the output when required, and
can deliver more depending on the conditions. Care must
be taken to limit the maximum output current by proper
choice of sense resistor and RIN and, if input fault con-
ditions exist, external clamps.
Output Filtering
The output voltage, VOUT, is simply IOUT ZOUT. This
makes filtering straightforward. Any circuit may be used
which generates the required ZOUT to get the desired filter
response. For example, a capacitor in parallel with ROUT
will give a lowpass response. This will reduce unwanted
noise from the output, and may also be useful as a charge
reservoir to keep the output steady while driving a switch-
ing circuit such as a MUX or ADC. This output capacitor
in parallel with an output resistor will create a pole in the
output response at:
f3dB 1
2 • • R
OUT
• C
OUT
Useful Equations
Input Voltage: VSENSE
ISENSE • RSENSE
Voltage Gain: VOUT
V
SENSE
ROUT
R
IN
Current Gain: IOUT
ISENSE
RSENSE
RIN
Transconductance: IOUT
VSENSE
1
RIN
Transimpedance: VOUT
I
SENSE
RSENSE ROUT
RIN
Power Supply Connection
For normal operation, the V+ pin should be connected to
either side of the sense resistor. Either connection will
meet the constraint that +IN ≤ V+ and –IN V+. During
normal operation, VSENSE should not exceed 500mV (see
VSENSE(MAX) under Electrical Characteristics). This addi-
tional constraint can be stated as V+ (+IN) 500mV.
Referring to Figure 5, feedback will force the voltages
at the inputs –IN and +IN to be equal to (VS VSENSE).
Connecting V
+
to the load side of the shunt results in equal
voltages at +IN, –IN and V+. Connecting V+ to the supply
end of the shunt results in the voltages at +IN and –IN to
be VSENSE below V+.
If the V+ pin is connected to the supply side of the shunt
resistor, the supply current drawn by the LT6107 is not
included in the monitored current. If the V+ pin is con-
nected to the load side of the shunt resistor (Figure 5),
the supply current drawn by the LT6107 is included in
the monitored current. It should be noted that in either
configuration, the output current of the LT6107 will not
be monitored since it is drawn through the RIN resistor
connected to the positive side of the shunt. Contact the
factory for operation of the LT6107 with a V+ outside of
the recommended operating range.
Figure 5. LT6107 Supply Current Monitored with the Load
Reverse Supply Protection
Some applications may be tested with reverse-polarity
supplies due to an expectation of the type of fault during
operation. The LT6107 is not protected internally from
external reversal of supply polarity. To prevent damage
that may occur during this condition, a Schottky diode
should be added in series with V (Figure 6). This will
limit the reverse current through the LT6107. Note that
this diode will limit the low voltage performance of the
LT6107 by effectively reducing the supply voltage to the
part by VD.
LT6107
ROUT
VOUT
6107 F05
RIN
VS
LOAD
RSENSE
+
V+
V
OUT
–IN+IN
LT6107 ‘I‘I
LT6107
11
6107fc
For more information www.linear.com/LT6107
APPLICATIONS INFORMATION
In addition, if the output of the LT6107 is wired to a
device that will effectively short it to high voltage (such
as through an ESD protection clamp) during a reverse
supply condition, the LT6107s output should be con-
nected through a resistor or Schottky diode (Figure 7).
Demo Board
Demo board DC1240 is available for evaluation of the
LT6107.
Response Time
The photos in the Typical Performance Characteristics
show the response of the LT6107 to a variety of input
conditions and values of RIN. The photos show that if the
output current is very low or zero and an input transient
occurs, there will be an increased delay before the output
voltage begins changing while internal nodes are being
charged.
Figure 6. Schottky Diode Prevents Damage During Supply Reversal Figure 7. Additional Resistor R3 Protects Output
During Supply Reversal
6107 F06
LT6107
R2
4.99k
D1
VBATT
R
SENSE
L
O
A
D
V+
V
OUT
–IN+IN
+
R1
100Ω
6107 F07
LT6107
R2
4.99k
D1
VBATT
R3
1k
R
SENSE
L
O
A
D
V+
V
OUT
–IN+IN
ADC
R1
100Ω
+
LT6107 12 suusARE vmusviu»nm\s 5 ans m EXELUSWE ur mum n s NULDMSHSHALLuunxciivuzsw so muss nmmcs s mum :5 Package
LT6107
12
6107fc
For more information www.linear.com/LT6107
PACKAGE DESCRIPTION
1.50 – 1.75
(NOTE 4)
2.80 BSC
0.30 – 0.45 TYP
5 PLCS (NOTE 3)
DATUM ‘A’
0.09 – 0.20
(NOTE 3) S5 TSOT-23 0302
PIN ONE
2.90 BSC
(NOTE 4)
0.95 BSC
1.90 BSC
0.80 0.90
1.00 MAX
0.01 – 0.10
0.20 BSC
0.30 – 0.50 REF
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
3.85 MAX
0.62
MAX
0.95
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
1.4 MIN
2.62 REF
1.22 REF
S5 Package
5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
Please refer to http://www.linear.com/product/LT6107#packaging for the most recent package drawings.
LT6107 13
LT6107
13
6107fc
For more information www.linear.com/LT6107
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER
C 02/18 Addition of H-Temperature Option for –40°C to 150°C Operation
Web links added
1-3
All
(Revision history begins at Rev C)
LT6107 1 4 I} SEGLé’ES
LT6107
14
6107fc
For more information www.linear.com/LT6107
LT 0218 REV C • PRINTED IN USA
www.linear.com/LT6107
ANALOG DEVICES, INC. 2008
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1787 Precision Bidirectional, High Side Current Sense Amplifier 75µV VOS, 60V, 60µA Operation
LT6100 Gain-Selectable High Side Current Sense Amplifier 4.1V to 48V, Pin-Selectable Gain: 10, 12.5, 20, 25, 40, 50V/V
LT C
®
6101/LTC6101HV High Voltage, High Side, Precision Current Sense Amplifiers 4V to 60V/5V to 100V, Gain Configurable, SOT-23
LTC6102/LTC6102HV Zero Drift High Side Current Sense Amplifier 4V to 60V/5V to 100V Operation, 10µV Offset, 1µs Step
Response, MSOP8/DFN
LTC6103 Dual High Side, Precision Current Sense Amplifier 4V to 60V, Gain Configurable 8-Pin MSOP
LTC6104 Bidirectional High Side, Precision Current Sense Amplifier 4V to 60V, Gain Configurable 8-Pin MSOP
LT6105 Rail-to-Rail Input Precision High Side Current Sense Amplifier –0.3V to 44V Input Common Mode Range, 300µV Offset,
1% Gain Accuracy, Gain Configurable
LT6106 Low Cost, High Side Precision Current Sense Amplifier 2.7V to 36V, Gain Configurable, SOT-23
TYPICAL APPLICATION
Simple 400V Current Monitor
6107 TA02
LT6107
RIN
100Ω
VOUT
ROUT
4.99k
L
O
A
D
+
VOUT = • VSENSE = 49.9 VSENSE
ROUT
RIN
M1 AND M2 ARE FQD3P50
M1
2M
12V
CMPZ12L
M2
400V
BAT46
VSENSE
RSENSE
ISENSE
+ –
DANGER! Lethal Potentials Present — Use Caution
DANGER!!
HIGH VOLTAGE!!
V+
V
OUT
–IN+IN

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