LTC2906, LTC2907 Datasheet by Analog Devices Inc.

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LTC2906/LTC2907 L7 "ILEICIJNOLOGY L7
LTC2906/LTC2907
1
29067f
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
Monitors Two Inputs Simultaneously
Three Threshold Selections for 5V, 3.3V or 2.5V
Supplies
Low Voltage Adjustable Input (0.5V)
Three Supply Tolerances (5%, 7.5%, 10%)
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage Over Temperature
Internal V
CC
Auto Select
Power Supply Glitch Immunity
200ms Reset Time Delay (LTC2906 Only)
Adjustable Reset Time Delay (LTC2907 Only)
Open Drain RST Output
Guaranteed RST for V1 1V or V
CC
1V
Low Profile (1mm) SOT-23 (ThinSOT
TM
) and
Plastic (3mm × 2mm) DFN Packages
Desktop and Notebook Computers
Handheld Devices
Network Servers
Core, I/O Monitor
Precision Dual Supply Monitors
with One Pin-Selectable Threshold
and One Adjustable Input
The LTC
®
2906/LTC2907 are dual supply monitors in-
tended for systems with multiple supply voltages. The
dual supply monitors have a common reset output with
delay (200ms for the LTC2906 and adjustable using an
external capacitor for the LTC2907). These products pro-
vide a precise, space-conscious and micropower solution
for supply monitoring.
The LTC2906/LTC2907 feature a tight 1.5% threshold
accuracy over the whole operating temperature range
and glitch immunity to ensure reliable reset operation
without false triggering. The open drain RST output state
is guaranteed to be in the correct state for V1 and/or V
CC
down to 1V.
The LTC2906/LTC2907 also feature one adjustable input
with a nominal threshold level at 0.5V, another input with
three possible input threshold levels, and three supply
tolerances for possible margining. These features provide
versatility for any kind of system requiring dual supply
monitors. Two three-state input pins program the thresh-
old and tolerance level without requiring any external
components.
, LTC and LT are registered trademarks of Linear Technology Corporation.
V1
V
CC
S1
TOL
V
ADJ
TMR
GND
RST
LTC2907
22nF
0.1µF
0.1µF
DC/DC
CONVERTER SYSTEM
LOGIC
29067 TA01
0.8V
2.5V
TOLERANCE = 10%
49.9k
100k
Dual Supply Monitor with Adjustable Tolerance (2.5V, 0.8V) Supply Selection Programming
V1 S1
5.0 V1
3.3 OPEN
2.5 GND
Tolerance Programming
TOLERANCE TOL
5% V1
7.5% OPEN
10% GND
“““““““
LTC2906/LTC2907
2
29067f
TOP VIEW
DDB8 PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
5
6
7
8
4
3
2
1
DDB8 PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
EXPOSED PAD IS GND (PIN 9),
MUST BE SOLDERED TO PCB
*RST FOR LTC2906
TMR FOR LTC2907
9
GND
RST
RST/TMR*
VCC
TOL
S1
VADJ
V1
Terminal Voltages
V1, V
CC
........................................................0.3V to 7V
S1, V
ADJ
, TOL ............................0.3V to (V
MAX
+ 0.3V)
RST .............................................................0.3V to 7V
RST (LTC2906)............................................0.3V to 7V
TMR (LTC2907)...........................................0.3V to 7V
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Notes 1, 2)
ELECTRICAL CHARACTERISTICS
The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = V1 = 2.5V, VADJ = 0.55V, S1 = TOL = 0V, unless otherwise noted.
(Notes 2, 3, 4)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT50
5V, 5% Reset Threshold V1 Input Threshold 4.600 4.675 4.750 V
5V, 7.5% Reset Threshold 4.475 4.550 4.625 V
5V, 10% Reset Threshold 4.350 4.425 4.500 V
V
RT33
3.3V, 5% Reset Threshold V1 Input Threshold 3.036 3.086 3.135 V
3.3V, 7.5% Reset Threshold 2.954 3.003 3.053 V
3.3V, 10% Reset Threshold 2.871 2.921 2.970 V
V
RT25
2.5V, 5% Reset Threshold V1 Input Threshold 2.300 2.338 2.375 V
2.5V, 7.5% Reset Threshold 2.238 2.275 2.313 V
2.5V, 10% Reset Threshold 2.175 2.213 2.250 V
V
RTADJ
ADJ, 5% Reset Threshold V
ADJ
Input Threshold 0.492 0.500 0.508 V
ADJ, 7.5% Reset Threshold 0.479 0.487 0.495 V
ADJ, 10% Reset Threshold 0.465 0.473 0.481 V
V
MAX(MIN)
Minimum V
MAX
Operating Voltage (Note 2) RST, RST in Correct Logic State 1V
I
VCC
V
CC
Input Current V
CC
> V1 54 100 µA
V1 > V
CC
±1µA
I
V1
V1 Input Current V
CC
> V1 13 µA
V1 > V
CC
55 100 µA
I
VADJ
V
ADJ
Input Current ±15 nA
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ORDER PART
NUMBER
DDB8 PART MARKING
T
JMAX
= 125°C, θ
JA
= 250°C/W
LBDC
LBDD
LBDF
LBDG
ORDER PART
NUMBER
TS8 PART MARKING
T
JMAX
= 125°C, θ
JA
= 250°C/W
LTC2906CDDB
LTC2906IDDB
LTC2907CDDB
LTC2907IDDB
LTC2906CTS8
LTC2906ITS8
LTC2907CTS8
LTC2907ITS8
Operating Temperature Range
LTC2906C/LTC2907C .............................. 0°C to 70°C
LTC2906I/LTC2907I ............................40°C to 85°C
Storage Temperature Range ..................65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
VCC 1
RST/TMR* 2
RST 3
GND 4
8 V1
7 VADJ
6 S1
5 TOL
TOP VIEW
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
*RST FOR LTC2906
TMR FOR LTC2907
LTBCM
LTBCN
LTBCP
LTBCQ
LTC2906/LTC2907
3
29067f
The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = V1 = 2.5V, VADJ = 0.55V, S1 = TOL = 0V, unless otherwise noted.
(Notes 2, 3, 4)
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The greater of V1, V
CC
is the internal supply voltage (V
MAX
).
Note 3: All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 4: For reset thresholds test conditions refer to the voltage threshold
programming table in the Applications Information section.
Note 5: The output pins RST and RST have an internal pull-up to V
MAX
of
typically –6µA. However, an external pull-up resistor may be used when
faster rise time is required or for V
OH
voltages greater than V
MAX
.
Note 6: The input current to the three-state input pins are the pull-up and
the pull-down current when the pins are either set to V1 or GND
respectively. In the open state, the maximum leakage current to V1 or GND
permissible is 10µA.
5V Threshold Voltage vs
Temperature 3.3V Threshold Voltage vs
Temperature 2.5V Threshold Voltage vs
Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
UW
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
TMR(UP)
TMR Pull-Up Current (LTC2907) V
TMR
= 0V 1.5 –2.1 –2.7 µA
I
TMR(DOWN)
TMR Pull-Down Current (LTC2907) V
TMR
= 1.4V 1.5 2.1 2.7 µA
t
RST
Reset Time-Out Period (LTC2906) 140 200 260 ms
t
RST
Reset Time-Out Period (LTC2907) C
TMR
= 22nF 140 200 260 ms
t
UV
V
X
Undervoltage Detect to V
X
Less Than Reset Threshold V
RTX
150 µs
RST or RST by More than 1%
V
OL
Output Voltage Low RST, RST I = 2.5mA 0.15 0.4 V
I = 100µA; V1 and/or V
CC
= 1V (RST Only) 0.05 0.3 V
V
OH
Output Voltage High RST, RST I = –1µA V
MAX
– 1 V
(Notes 2, 5)
Three-State Inputs S1, TOL
V
IL
Low Level Input Voltage 0.4 V
V
IH
High Level Input Voltage 1.4 V
V
Z
Pin Voltage when Left in Hi-Z State I = –10µA0.7 V
I = 0µA 0.9 V
I = 10µA1.1 V
I
VPG
Programming Input Current (Note 6) ±25 µA
Specifications are at TA = 25°C unless otherwise noted.
TEMPERATURE (°C)
THRESHOLD VOLTAGE, V
RT50
(V)
29067 G01
TEMPERATURE (°C) TEMPERATURE (°C)
THRESHOLD VOLTAGE, V
RT33
(V)
3.12
3.07
3.02
2.97
2.92
2.87
29067 G02
THRESHOLD VOLTAGE, V
RT25
(V)
29067 G03
2.375
2.325
2.275
2.225
2.175
4.75
4.70
4.65
4.60
4.55
4.50
4.45
4.40
4.35
–50 100
25 75
–25 050 –50 100
25 75
–25 050 –50 100
25 75
–25 050
5%
7.5%
10%
5%
7.5%
10%
5%
7.5%
10%
L7 WW
LTC2906/LTC2907
4
29067f
COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX)
0.1
TYPICAL TRANSIENT DURATION (µs)
700
600
500
400
300
200
100
01 10 100
29067 G07
RESET OCCURS
ABOVE CURVE
CTMR (FARAD)
10p 100p 1n 10n 100n 1µ
RESET TIME OUT PERIOD, tRST (ms)
29067 G08
10000
1000
100
10
1
0.1
TEMPERATURE (°C)
RESET TIME OUT PERIOD, tRST (ms)
29067 G09
235
230
225
220
215
210
205
200
195
THRESHOLD VOLTAGE, VRTADJ (V)
0.505
0.500
0.495
0.490
0.485
0.480
0.475
0.470
IV1 (µA)
19.5
19.0
18.5
18.0
17.5
17.0
IVCC (µA)
15.8
15.6
15.4
15.2
15.0
14.8
14.6
14.4
14.2
14.0
29067 G06
TEMPERATURE (°C)
29067 G0529067 G04
29067 G12
29067 G1129067 G10
TEMPERATURE (°C)
5%
7.5%
V1 (V)
0
RST OUTPUT VOLTAGE (V)
5
4
3
2
1
0
–1 12345
S1 = TOL = VCC = V1
VADJ = 0.55V
10k PULL-UP RESISTOR
V1 (V)
0
RST OUTPUT VOLTAGE (V)
5
4
3
2
1
0
–1 12345
V1 (V)
0
RST OUTPUT VOLTAGE (V)
5
4
3
2
1
0
–1 12345
10%
–50 100
25
TEMPERATURE (°C)
75
–25 050 –50 100
25 75
–25 050
V1 = 5V
VCC = 3.3V
VADJ =0.55V
S1 =TOL = 1.4V
–50 100
25 75
–25 050
–50 100
25 75
–25 050
V1 = 2.5V
VCC = 3.3V
VADJ =0.55V
S1 =TOL = 1.4V
S1 = TOL = VCC = V1
VADJ = 0.55V
10k PULL-UP RESISTOR
S1 = TOL = VCC = V1
VADJ = 0.55V
10pF CAPACITOR AT RST
CRT = 22nF
(FILM)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
ADJ Threshold Voltage vs
Temperature IV1 vs Temperature IVCC vs Temperature
Typical Transient Duration vs
Comparator Overdrive (V1, VADJ)Reset Time Out Period (tRST)
vs Capacitance (CTMR)
Reset Time Out Period (tRST)
vs Temperature
RST Output Voltage vs V1 RST Output Voltage vs V1
RST Output Voltage vs V1
Specifications are at TA = 25°C unless otherwise noted.
RST AT ‘somv / / / /R/ ST AT sumv i \\ we / / w ”1 I
LTC2906/LTC2907
5
29067f
29067 G13 29067 G14
29067G17
29067 G21
29067G15
V
MAX
(V)
0
RST PULL-DOWN CURRENT, I
RST
(mA)
5
4
3
2
1
04123 5
RST AT 150mV
RST AT 50mV
RST PULL-DOWN CURRENT, I
RST
(mA)
0
RST OUTPUT VOLTAGE LOW, V
OL
(V)
20
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
29067 G18
10 50 604030
25°C
85°C
–40°C
29067 G19
TEMPERATURE (°C)
I
S1
, I
TOL
(µA)
20
19
18
17
16
15
14
13
12
11
10
V
MAX
(V)
0
RST PULL-DOWN CURRENT, I
RST
(mA)
5
4
3
2
1
04123 5
RST AT 150mV
RST AT 50mV
V
CC
= V1
S1 = TOL = GND
V
ADJ
= 0.55V
NO PULL-UP R
V1 = V
CC
= 5V
V
ADJ
= 0.45V
S1 = TOL = V1
NO PULL-UP R
S1 = TOL = V
CC
= V1
V
ADJ
= 0.55V
NO PULL-UP R
RST PULL-DOWN CURRENT, I
RST
(mA)
0
RST OUTPUT VOLTAGE LOW, V
OL
(V)
20
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
29067 G16
10 50 604030
25°C
85°C
–40°C
V
MAX
(V)
2.0 4.0
3.0 5.02.5 4.5
3.5
RST PULL-UP CURRENT, I
RST
(µA)
–16
–14
–12
–10
–8
–6
–4
–2
0
TOL = V1
V
RT25
V
RT33
V
RT50
V
MAX
(V)
2.0
RST PULL-UP CURRENT, I
RST
(µA)
4.0
–18
–16
–14
–12
–10
–8
–6
–4
–2
03.0 5.02.5 4.5
3.5
V
RT25
V
RT33
V
RT50
TOL = GND
OUTPUT SOURCE CURRENT, I
RST
(µA)
–12
RST OUTPUT VOLTAGE HIGH, V
OH
(V)
3.0
2.5
2.0
1.5
1.0
0.5 –10 –8 –6 –4 –2 0
25°C
85°C
–40°C
OUTPUT SOURCE CURRENT, I
RST
(µA)
–7
RST OUTPUT VOLTAGE HIGH, V
OH
(V)
3.5
3.0
2.5
2.0
1.5
1.0
0.5 –1
–8 –6 3–4–5
290467 G20
–2 0
TOL = V1 = 3.3V
V
ADJ
= 0.45V
S1 = OPEN
NO PULL-UP R
TOL = V1 = 3.3V
V
ADJ
= 0.55V
S1 = OPEN
NO PULL-UP R
25°C
85°C
40°C
V1 = V
CC
= 5V
V
ADJ
= 0.55V
S1 = TOL = V1
NO PULL-UP R
–50 100
25 75
–25 050
S1 = TOL = V1 = 3.3V
TYPICAL PERFOR A CE CHARACTERISTICS
UW
RST Pull-Down Current (IRST)
vs VMAX
RST Pull-Up Current (IRST)
vs VMAX
RST Output Voltage Low (VOL)
vs RST Pull-Down Current (IRST)
RST Pull-Down Current (IRST)
vs VMAX
RST Output Voltage Low (VOL)
vs RST Pull-Down Current (IRST)RST Pull-Up Current (IRST)
vs VMAX
RST Output Voltage High (VOH)
vs RST Output Source Current (IRST)RST Output Voltage High (VOH) vs
RST Output Source Current (IRST)I
S1, ITOL vs Temperature
Specifications are at TA = 25°C unless otherwise noted.
LTC2906/LTC2907
6
29067f
UU
U
PI FU CTIO S
V
CC
(Pin 1/Pin 4): Optional Power Supply Pin. V
CC
powers
and maintains the correct operation of the RST and RST
pins in the complete absence of V1. If V1 is present, the
greater of V
CC
or V1 (V
MAX
) powers the internal circuitry
and the reset outputs. Bypass this pin to ground with a
0.1µF (or greater) capacitor. Tie to V1 when no optional
power is available.
RST (Pin 2/Pin 3): (LTC2906 Only) Reset Logic Output.
When all voltage inputs are above the reset threshold for
at least the programmed delay time, this pin pulls low. This
pin has a weak pull up to V
MAX
and may be pulled above
V
MAX
using an external pull-up.
TMR (Pin 2/Pin 3): (LTC2907 Only) Reset Delay Time
Programming Pin. Attach an external capacitor (C
TMR
) to
GND to set a reset delay time of 9ms/nF. Leaving the pin
open generates a minimum delay of approximately 200µs.
A 22nF capacitor will generate a 200ms reset delay time.
RST (Pin 3/Pin 2): Inverted Reset Logic Output. Pulls low
when either V1 or V
ADJ
is below the reset threshold and
holds low for programmed delay time after all voltage
inputs are above threshold. This pin has a weak pull up to
V
MAX
and may be pulled above V
MAX
using an external
pull-up.
GND (Pin 4/Pin 1 and Pin 9): Ground.
TOL (Pin 5/Pin 8): Three-State Input for Supply Tolerance
Selection (5%, 7.5% or 10%). Refer to Applications Infor-
mation for tolerance selection chart (Table 3).
S1 (Pin 6/Pin 7): The Voltage Threshold Select Three-
State Input. Connect to V1, GND or leave unconnected in
open state to select one of three possible input threshold
levels (refer to Table 1).
V
ADJ
(Pin 7/Pin 6): Adjustable Voltage Input. Bypass this
pin to ground with a 0.1µF (or greater) capacitor in a noisy
environment.
V1 (Pin 8/Pin 1): Voltage Input 1. Select from 5V, 3.3V or
2.5V. Refer to Table 1 for details. The greater of (V1, V
CC
)
is also the internal V
CC
(V
MAX
). Bypass this pin to ground
with a 0.1µF (or greater) capacitor.
(TS8 Package/DDB8 Package)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
TEMPERATURE (°C)
I
S1
, I
TOL
(µA)
–20
–19
–18
–17
–16
–15
–14
–13
–12
–11
–10
29067 G22
–50 100
25 75
–25 050
S1 = TOL = GND
V1 = 3.3V
IS1, ITOL vs Temperature
Specifications are at TA = 25°C unless otherwise noted.
IPA—4L TD 9 fl » » a .|_
LTC2906/LTC2907
7
29067f
BLOCK DIAGRA
W
+
+
200ms
RESET PULSE
GENERATOR
THREE-STATE DECODER
RESISTOR
NETWORK
POWER
DETECT
BAND GAP
REFERENCE
V
MAX
V
MAX
LTC2906
2906 BD
S1 TOL
RST
RST
V
MAX
GND
V1
V
ADJ
V
CC
6µA
6µA
+
+
200ms
RESET PULSE
GENERATOR
THREE-STATE DECODER
RESISTOR
NETWORK
POWER
DETECT
BAND GAP
REFERENCE
V
MAX
V
MAX
LTC2907
2907 BD
S1 TOL
TMR
RST
GND
V1
V
CC
V
ADJ
6µA
L7L'F1EN2
LTC2906/LTC2907
8
29067f
APPLICATIO S I FOR ATIO
WUUU
Supply Monitoring
The LTC2906/LTC2907 are low power, high accuracy dual
supply monitoring circuits with an adjustable input and
another input with selectable threshold. Reset delay is set
to a nominal of 200ms for LTC2906 and is adjustable using
an external capacitor for LTC2907.
The three-state input pin (S1) selects one of three possible
threshold voltage levels for V1. Another three-state input
pin sets the supply tolerance (5%, 7.5% or 10%). Both
input voltages (V1 and V
ADJ
) must be above predeter-
mined thresholds for the reset not to be invoked. The
LTC2906/LTC2907 assert the reset outputs during power-
up, power-down and brownout conditions on any one of
the voltage inputs.
Power-Up
The greater of V1, V
CC
is the internal supply voltage
(V
MAX
). V
MAX
powers the drive circuits for the RST pin.
Therefore, as soon as V1 or V
CC
reaches 1V during power
up, the RST output asserts low.
V
MAX
also powers the drive circuits for the RST pin in the
LTC2906. Therefore, RST weakly pulls high when either
V1 or V
CC
reaches at least 1V.
Threshold programming is complete, when V1 reaches at
least 2.17V. After programming, if any one of the Vx inputs
TI I G DIAGRA
UWW
V
X
RST
RST
t
UV
t
RST
1V
1V
V
RTX
29067 TD
Vx Monitor Timing
falls below its programmed threshold, RST asserts low
(RST weakly pulls high) as long as V
MAX
is at least 1V.
Once both V1 and V
ADJ
inputs rise above their thresholds,
an internal timer is started. After the programmed delay
time, RST weakly pulls high (RST asserts low).
Power-Down
On power-down, once either V1 or V
ADJ
drops below its
threshold, RST asserts logic low and RST weakly pulls
high. V
MAX
of at least 1V guarantees a logic low of 0.4V
at RST.
Auxiliary Power
If an auxiliary power is available it can be connected to the
V
CC
pin. Since the internal supply voltage (V
MAX
) is the
greater of V1, V
CC
; a V
CC
of at least 1V guarantees logic low
of 0.4V at RST for voltage inputs (V1 and/or V
ADJ
) down
to 0V.
Programming Pins
The two three-state input pins, S1 and TOL, should be
connected to GND, V1 or left unconnected during normal
operation. Note that when left unconnected, the maximum
leakage current allowable from the pin to either GND or V1
is 10µA.
LTC2906/LTC2907
9
29067f
In margining application, the three-state input pins can be
driven using a three-state buffer. Note however, the low
and high output of the three-state buffer has to satisfy the
V
IL
and V
IH
of the three-state pin listed in the Electrical
Characteristics Table. Moreover, when the three-state
buffer is in the high impedance state, the maximum
leakage current allowed from the pin to either GND or V1
is 10µA.
Monitor Programming
Connecting S1 to either GND, or V1, or leaving it in open
state selects the LTC2906/LTC2907 V1 input voltage
threshold. Table 1 shows the three possible selections of
V1 nominal input voltage and their corresponding S1
connection.
The noninverting input on the V
ADJ
comparator is set
to 0.5V when the TOL pin is set high (5% tolerance)
(Figure␣ 1) and the high impedance inverting input directly
ties to the V
ADJ
pin.
Table 1. Supply Selection Programming
V1 S1
5.0 V1
3.3 OPEN
2.5 GND
Note: Open = open circuit or driven by a three-state buffer
in high impedance state with leakage current less than 10µA.
R2 =100k is recommended. Once the resistor divider is
set in the 5% tolerance mode, there is no need to change
the divider for the other tolerance modes (7.5%, 10%)
because the internal reference at the noninverting input on
the V
ADJ
comparator is scaled accordingly, moving the trip
point in 2.5% decrements.
Table 2 shows suggested 1% resistor values for various
adjustable applications.
Table 2. Suggested 1% Resistor Values for the VADJ Inputs
V
SUPPLY
(V) V
TRIP
(V) R1 (k) R2 (k)
12 11.25 2150 100
10 9.4 1780 100
8 7.5 1400 100
7.5 7 1300 100
6 5.6 1020 100
5 4.725 845 100
3.3 3.055 511 100
3 2.82 464 100
2.5 2.325 365 100
1.8 1.685 237 100
1.5 1.410 182 100
1.2 1.120 124 100
1 0.933 86.6 100
0.9 0.840 68.1 100
0.8 0.750 49.9 100
0.7 0.655 30.9 100
0.6 0.561 12.1 100
Tolerance Programming
The three-state input pin TOL, programs the common
supply tolerance for both V1 and V
ADJ
input voltages (5%,
7.5% or 10%). The larger the tolerance the lower the trip
threshold. Table 3 shows the tolerances selection corre-
sponding to a particular connection at the TOL pin.
+
+
0.5V
LTC2906/LTC2907
R1
1%
R2
1%
V
TRIP
V
ADJ
29067 F01
Figure 1. Setting the Adjustable Trip Point
In a typical application, the V
ADJ
pin connects to a tap point
on an external resistive divider between the positive volt-
age being monitored and ground. The following formula
obtains R1 resistor value for a particular value of R2 and
a desired trip voltage at 5% tolerance:
RV
VR
TRIP
105 12
5
=
(%)
.
APPLICATIO S I FOR ATIO
WUUU
Table 3. Tolerance Programming
TOLERANCE TOL
5% V1
7.5% OPEN
10% GND
LTC2906/LTC2907
10
29067f
Threshold Accuracy
Reset threshold accuracy is of the utmost importance in a
supply sensitive system. Ideally such a system should not
reset while supply voltages are within a specified margin
below the rated nominal level. Both of the LTC2906/
LTC2907 inputs have the same relative threshold accu-
racy. The specification for LTC2906/LTC2907 is ±1.5% of
the programmed nominal input voltage (over the full
operating temperature range).
For example, when the LTC2906/LTC2907 are programmed
to handle a 5V input with 10% tolerance (S1 = V1 and TOL
= GND, refer to Table 1 and Table 3), it does not issue a
reset command when V1 is above 4.5V. The typical 10%
trip threshold is at 11.5% below the nominal input voltage
level. Therefore, the typical trip threshold for the 5V input
is 4.425V. With ±1.5% accuracy, the trip threshold range
is 4.425V ±75mV over temperature (i.e. 10% to 13%
below 5V). This implies that the monitored system must
operate reliably down to 4.35V or 13% below 5V over
temperature.
The same system using a supervisor with only ±2.5%
accuracy needs to work reliably down to 4.25V (4.375V
±125mV) or 15% below 5V, requiring the monitored
system to work over a much wider operating voltage
range.
In any supervisory application, supply noise riding on the
monitored DC voltage can cause spurious resets, particu-
larly when the monitored voltage is near the reset thresh-
old. A less desirable but common solution to this problem
is to introduce hysteresis around the nominal threshold.
Notice however, this hysteresis introduces an error term
in the threshold accuracy. Therefore, a ±2.5% accurate
monitor with ±1% hysteresis is equivalent to a ±3.5%
monitor with no hysteresis.
The LTC2906/LTC2907 take a different approach to solve
this problem of supply noise causing spurious reset. The
first line of defense against this spurious reset is a first
order low pass filter at the output of the comparator. Thus,
the comparator output goes through a form of integration
before triggering the output logic. Therefore, any kind of
transient at the input of the comparator needs to be of
sufficient magnitude and duration before it can trigger a
change in the output logic.
The second line of defense is the programmed delay time
t
RST
(200ms for LTC2906 and adjustable using an external
capacitor for LTC2907). This delay will eliminate the effect
of any supply noise, whose frequency is above 1/ t
RST
, on
the RST and RST output.
When either V1 or V
ADJ
drops below its programmed
threshold, the RST pin asserts low (RST weakly pulls
high). When the supply recovers above the programmed
threshold, the reset-pulse-generator timer starts
counting.
If the supply remains above the programmed threshold
when the timer finishes counting, the RST pin weakly pulls
high (RST asserts low). However, if the supply falls below
the programmed threshold any time during the period
when the timer is still counting, the timer resets and starts
fresh when the supply next rises above the programmed
threshold.
Note that this second line of defense is only effective for a
rising supply and does not affect the sensitivity of the
system to a falling supply. Therefore, the first line of
defense that works for both cases of rising and falling is
necessary. These two approaches prevent spurious reset
caused by supply noise without sacrificing the threshold
accuracy.
Selecting the Reset Timing Capacitor
The reset time-out period for LTC2907 is adjustable in
order to accommodate a variety of microprocessor appli-
cations. Connecting a capacitor, C
TMR
, between the TMR
pin and ground sets the reset time-out period, t
RST
. The
following formula determines the value of capacitor needed
for a particular reset time-out period:
C
TMR
= t
RST
• 110 • 10
–9
[F/s]
For example, using a standard capacitor value of 22nF
gives a 200ms delay.
The graph in Figure 2 shows the desired delay time as a
function of the value of the timer capacitor that should be
used:
APPLICATIO S I FOR ATIO
WUUU
VMAX
LTC2906/LTC2907
11
29067f
Leaving the TMR pin open with no external capacitor
generates a reset time-out of approximately 200µs. For
long reset time-out, the only limitation is the availability of
a large value capacitor with low leakage. The TMR capaci-
tor will never charge if the leakage current exceeds the
TMR charging current of 2.1µA (typical).
RST and RST Output Characteristics
The DC characteristics of the RST and RST pull-up and
pull-down strength are shown in the Typical Performance
Characteristics section. Both RST and RST have a weak
internal pull-up to V
MAX
and a strong pull-down to ground.
The weak pull-up and strong pull-down arrangement
allows these two pins to have open-drain behavior while
possessing several other beneficial characteristics.
The weak pull-ups eliminate the need for external pull-up
resistors when the rise time on these pins is not critical. On
the other hand, the open-drain RST configuration allows
for wired-OR connections and can be useful when more
than one signal needs to pull-down on the RST line.
As noted in the Power-Up and Power-Down sections, the
circuits that drive RST and RST are powered by V
MAX
=
MAX (V1, V
CC
). During fault condition, V
MAX
of at least 1V
guarantees a maximum V
OL
= 0.4V at RST. However, at
V
MAX
= 1V the weak pull-up current on RST is barely turned
on. Therefore, an external pull-up resistor of no more than
100k is recommended on the RST pin if the state and pull-
up strength of the RST pin is crucial at very low V
MAX
.
Note however, by adding an external pull-up resistor, the
pull-up strength on the RST pin is increased. Therefore, if
it is connected in a wired-OR connection, the pull-down
strength of any single device needs to accommodate this
additional pull-up strength.
Output Rise and Fall Time Estimation
The RST and RST output have strong pull-down capability.
The following formula estimates the output fall time (90%
to 10%) for a particular external load capacitance (C
LOAD
):
t
FALL
2.2␣ •␣ R
PD
␣•␣C
LOAD
where R
PD
is the on-resistance of the internal pull-down
transistor estimated to be typically 40 at V
MAX
>1V, at
room temperature (25°C), and C
LOAD
is the external load
capacitance on the pin. Assuming a 150pF load capaci-
tance, the fall time is about 13ns.
The rise time on the RST and RST pins is limited by weak
internal pull-up current sources to V
MAX
. The following
formula estimates the output rise time (10% to 90%) at the
RST and RST pins:
t
RISE
2.2 • R
PU
• C
LOAD
where R
PU
is the on-resistance of the pull-up transistor.
Notice that this pull-up transistor is modeled as a
6µA current source in the Block Diagram as a typical
representation.
The on-resistance as a function of the V
MAX
= MAX (V1,
V
CC
) voltage (for V
MAX
> 1V) at room temperature is
estimated as follows:
RMAX V V V
PU CC
=Ω
610
11
5
(, )
At V
MAX
= 3.3V, R
PU
is about 260k. Using 150pF for load
capacitance, the rise time is 86µs. A smaller external pull-
up resistor maybe used if the output needs to pull up faster
and/or to a higher voltage. For example, the rise time
reduces to 3.3µs for a 150pF load capacitance, when using
a 10k pull-up resistor.
APPLICATIO S I FOR ATIO
WUUU
C
TMR
(FARAD)
10p 100p 1n 10n 100n 1µ
RESET TIME OUT PERIOD, t
RST
(ms)
29067 F02
10000
1000
100
10
1
0.1
Figure 2. Reset Time-Out Period vs Capacitance
LTC2906/LTC2907
12
29067f
V1
TOL
S1
TMR
RST
V
CC
V
ADJ
GND
LTC2906 1.8V 5V
3.3V
0.1µF
0.1µF
22nF
2907 TA03
237k
100k
SYSTEM
RESET
3.3V, 1.8V Monitor, 7.5% Tolerance
with an Auxiliary 5V Supply (5V Not Monitored)
TYPICAL APPLICATIO S
U
V1
TOL
S1
RST
RST
V
CC
V
ADJ
GND
LTC2906
5V3.3V
0.1µF
0.1µF
SYSTEM
RESET
2906 TA02
845k
100k
P0WER
GOOD
LED
499
5V, 3.3V Supply Monitor, 5% Tolerance
with LED Power Good Indicator
_I___ \w i1. 1.
LTC2906/LTC2907
13
29067f
V
ADJ
GND
RST
V1
V
CC
S1
RST
TOL
LTC2906
5V
3.3V
0.1µF
SYSTEM
RESET
2906 TA05
511k
100k
10k
V1
V
CC
RST
S1
V
ADJ
TMR
TOL
GND
LTC2907
1V
2.5V
5V 0.1µF
0.1µF
0.1µF
2907 TA04
22nF
499
LED
100k
86.6k
2.5V, 1V Monitor, 10% Tolerance with LED Undervoltage Indicator
and 5V High Availability Auxiliary Supply (5V Not Monitored)
Dual Supply Monitor with Hysteresis, 5% Tolerance
(Supplies Rising), 10% Tolerance (After RST Goes Low)
TYPICAL APPLICATIO S
U
C
GATE
10nF
V
CC
R
ONB
154k
3.3V
R
TB1
R
TB2
R
FA1
R
FB1
R
TA2
237k
100k
R
TA1
R
ONA
100k
ON FB1
GATE
LTC2923
GND
292067 TA06
RAMP
R
FA2
R
FB2
RAMPBUF
TRACK1
TRACK2 FB2
DC/DC
IN
FB OUT
DC/DC
IN
FB OUT
0.1µF
0.1µF
22nF
RST
TMR
V1
TOL
V
ADJ
S1
LTC2907
SYSTEM
1.8V
2.5V
V
CC
GND
Dual Supply Monitor for Tracked/Sequenced Supply
w j W L94. L7L'F1EN2
LTC2906/LTC2907
14
29067f
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702)
U
PACKAGE DESCRIPTIO
2.00 ±0.10
(2 SIDES)
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
0.38 ± 0.10
BOTTOM VIEW—EXPOSED PAD
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
R = 0.115
TYP
2.15 ±0.05
(2 SIDES)
3.00 ±0.10
(2 SIDES)
14
85
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0 – 0.05
(DDB8) DFN 1103
0.25 ± 0.05
2.20 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.61 ±0.05
(2 SIDES)
1.15 ±0.05
0.675 ±0.05
2.50 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05 0.50 BSC
PIN 1
CHAMFER OF
EXPOSED PAD
0.50 BSC
+13; fl I+ LI fiw L fig 1 _ fl i T
LTC2906/LTC2907
15
29067f
PACKAGE DESCRIPTIO
U
1.50 – 1.75
(NOTE 4)
2.80 BSC
0.22 – 0.36
8 PLCS (NOTE 3)
DATUM ‘A’
0.09 – 0.20
(NOTE 3)
TS8 TSOT-23 0802
2.90 BSC
(NOTE 4)
0.65 BSC
1.95 BSC
0.80 – 0.90
1.00 MAX 0.01 – 0.10
0.20 BSC
0.30 – 0.50 REF
PIN ONE ID
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
0.52
MAX 0.65
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
1.4 MIN
2.62 REF
1.22 REF
TS8 Package
8-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1637)
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
MM— ICE" =T= __| IT" '1'? L7L'F1EN2
LTC2906/LTC2907
16
29067f
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
FAX: (408) 434-0507
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2004
LT/TP 0304 1K • PRINTED IN USA
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TYPICAL APPLICATIO
U
PART NUMBER DESCRIPTION COMMENTS
LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65V Threshold
LTC694-3.3 3.3V Supply Monitor, Watchdog Timer and Battery Backup 2.9V Threshold
LTC699 5V Supply Monitor and Watchdog Timer 4.65V Threshold
LTC1232 5V Supply Monitor, Watchdog Timer and Push-Button Reset 4.37V/4.62V Threshold
LTC1326/LTC1326-2.5 Micropower Precision Triple Supply Monitor for 4.725V, 3.118V, 1V Threshold (±0.75%)
5V/2.5V, 3.3V and ADJ
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LTC1726-2.5/LTC1726-5 Micropower Triple Supply Monitor for Adjustable RESET and Watchdog Time-Outs
2.5V/5V, 3.3V and ADJ
LTC1727-2.5/ LTC1727-5 Micropower Triple Supply Monitor with Open-Drain Reset Individual Monitor Outputs in MSOP
LTC1728-1.8/ LTC1728-3.3 Micropower Triple Supply Monitor with Open-Drain Reset 5-Lead SOT-23 Package
LTC1728-2.5/ LTC1728-5 Micropower Triple Supply Monitor with Open-Drain Reset 5-Lead SOT-23 Package
LTC1985-1.8 Micropower Triple Supply Monitor with 5-Lead SOT-23 Package
Push-Pull Reset Output
LTC2900 Programmable Quad Supply Monitor Adjustable RESET, 10-Lead MSOP and
3mm X 3mm 10-Lead DFN Packages
LTC2901 Programmable Quad Supply Monitor Adjustable RESET and Watchdog Timer,
16-Lead SSOP Package
LTC2902 Programmable Quad Supply Monitor Selectable Tolerance, RESET Disable for Margining
Functions, 16-Lead SSOP Package
LTC2903 Precision Quad Supply Monitor Ultralow Voltage RESET, 6-Lead SOT-23 Package
LTC2904 Three-State Programmable Precision Dual Supply Monitor Adjustable Tolerance, 8-Lead SOT-23 and
3mm × 2mm DFN Packages
LTC2905 Three-State Programmable Precision Dual Supply Monitor Adjustable RESET and Tolerance, 8-Lead SOT-23 and
3mm × 2mm DFN Packages
V
ADJ
TMR
S1
GND
V1
V
CC
TOL
RST
LTC2907 V1
TOL
V
CC
S1
GND
RST
V
ADJ
TMR
LTC2907
3.3V 2.5V
0.8V 0.6V
0.1µF0.1µF
2907 TA07
22nF
12.1k
100k
49.9k
100k
22nF
499
LED
Quad Supply Monitor with LED Undervoltage
Indicator, 5% Tolerance, 3.3V, 2.5V, 0.8V, 0.6V

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