LINER LTC1727ES8-5 Micropower precision triple supply monitors in 8-lead msop and 5-lead sot-23 package Datasheet

LTC1727/LTC1728
Micropower Precision
Triple Supply Monitors
in 8-Lead MSOP and
5-Lead SOT-23 Packages
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FEATURES
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DESCRIPTIO
Monitors Three Inputs Simultaneously
LTC1727-5: 5V, 3.3V and ADJ
LTC1727-2.5: 2.5V, 3.3V and ADJ
LTC1728-5: 5V, 3.3V and ADJ
LTC1728-2.5: 2.5V, 3.3V and ADJ
LTC1728-1.8: 3V, 1.8V and ADJ
±1.5% Threshold Accuracy Over Temperature
Very Low Supply Current: 10µA Typ
200ms Reset Time Delay
Active Low RESET Output
Power Supply Glitch Immunity
Guaranteed RESET for VCC3 ≥ 1V
or VCC5 /VCC25/VCC18 ≥ 1V
LTC1727 Includes Monitor Output for Each Supply
LTC1727: 8-Lead MSOP and SO Packages
LTC1728: 5-Lead SOT-23 Package
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APPLICATIO S
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The LTC1728 is functionally identical to the LTC1727
without the individual monitor outputs.
The RST output is guaranteed to be in the correct state for
VCC5/VCC25/VCC18 or VCC3 down to 1V. The LTC1727/
LTC1728 may also be configured to monitor any one or
two VCC inputs instead of three, depending on system
requirements.
Very low (10µA typical) supply current makes the LTC1727/
LTC1728 ideal for power conscious systems.
The LTC1727 is available in an 8-lead MSOP or SO
package and the LTC1728 is available in a 5-lead SOT-23
package.
Desktop Computers
Notebook Computers
Intelligent Instruments
Portable Battery-Powered Equipment
Network Servers
, LTC and LT are registered trademarks of Linear Technology Corporation.
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The LTC®1727 is a triple supply monitor intended for
systems with multiple supply voltages. Each supply monitor has its own open-drain output for individual supply
monitoring. A common open-drain reset output remains
low until all three supplies have been in compliance for
200ms. Tight 1.5% accuracy specifications and glitch
immunity ensure reliable reset operation without false
triggering.
TYPICAL APPLICATIO
DC/DC
CONVERTER
3.3V
5V
1.8V
SYSTEM
LOGIC
5
VCC3
RST
Triple Supply Monitor with Power Good Output
(3.3V, 2.5V and Adjustable)
LTC1727-2.5
1
3.3V
LTC1728-5
0.1µF
0.1µF
4
VCC5
R1
61.9k
1% 3
VCCA
R2
100k
1%
2.5V
GND
1727/28 TA01
2
ADJUSTABLE
SUPPLY
R1
1
2
3
R2
4
VCC3
COMP3
VCC25 COMP25
VCCA
RST
GND
COMPA
8
R3
10k
R4
10k
POWER
GOOD
7
6
SYSTEM
RESET
5
1727/28 TA08
1
LTC1727/LTC1728
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ABSOLUTE
RATI GS (Notes 1, 2)
VCC3, VCC5/VCC25/VCC18, VCCA ................... – 0.3V to 7V
RST ........................................................... – 0.3V to 7V
COMPA, COMP3, COMP25/COMP5
(MS8 and SO-8 Only) ............................ – 0.3V to 7V
Operating Temperature Range
(Note 3) ............................................. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................ 300°C
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PACKAGE/ORDER I FOR ATIO
TOP VIEW
TOP VIEW
TOP VIEW
VCC3
VCC5 /VCC25
VCCA
GND
1
2
3
4
8
7
6
5
COMP3
COMP25/COMP5
RST
COMPA
MS8 PACKAGE
8-LEAD PLASTIC MSOP
VCC3 1
VCC5/
2
VCC25
VCCA 3
8
GND 4
5
COMP3
COMP25/
COMP5
RST
7
6
RST 1
VCC5/
4 VCC25 /
VCC18
VCCA 3
COMPA
S5 PACKAGE
5-LEAD PLASTIC SOT-23
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 200°C/W
5 VCC3
GND 2
TJMAX = 125°C, θJA = 250°C/W
TJMAX = 125°C, θJA = 150°C/W
ORDER
PART NUMBER
MS8
PART MARKING
ORDER
PART NUMBER
S8
PART MARKING
ORDER
PART NUMBER
S5
PART MARKING
LTC1727EMS8-2.5
LTC1727EMS8-5
LTHY
LTHX
LTC1727ES8-2.5
LTC1727IS8-2.5
LTC1727ES8-5
LTC1727IS8-5
172725
727I25
17275
1727I5
LTC1728ES5-1.8
LTC1728ES5-2.5
LTC1728ES5-5
LTPH
LTIA
LTHZ
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
All except LTC1728-1.8. The ● denotes specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VRT3
Reset Threshold VCC3
VCC3 Input Threshold
●
3.036
3.086
3.135
V
VRT5
Reset Threshold VCC5
VCC5 Input Threshold (5V Version)
●
4.600
4.675
4.750
V
VRT25
Reset Threshold VCC25
VCC25 Input Threshold (2.5V Version)
●
2.300
2.338
2.375
V
VRTA
Reset Threshold VCCA
VCCA Input Threshold
●
0.985
1.000
1.015
V
VCCOP
VCC3, VCC5/VCC25 Operating Voltage
RST, COMP3, COMP5, COMP25 in Correct Logic State
●
1
7
V
VCCOPA
VCC3, VCC5/VCC25 Operating Voltage
Minimum Supply Voltage to Guarantee COMPA
in Correct Logic State
●
2
2.3
V
IVCC3
VCC3 Supply Current
VCC5/VCC25 > VCC3
VCC5/VCC25 < VCC3, VCC3 = 3.3V (Note 4)
●
●
1
10
2
20
µA
µA
IVCC25
VCC25 Supply Current
VCC25 < VCC3, VCC25 = 2.5V (Note 4)
●
1
2
µA
IVCC5
VCC5 Supply Current
VCC5 = 5V, VCC3 < VCC5
●
10
20
µA
IVCCA
VCCA Input Current
VCCA = 1V
●
– 15
0
15
nA
tRST
Reset Pulse Width
RST Low with 10k Pull-Up to VCC3 (Note 5)
●
140
200
280
ms
2
LTC1727/LTC1728
ELECTRICAL CHARACTERISTICS
All except LTC1728-1.8. The ● denotes specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
tUV
VCC Undervoltage Detect to RST
or COMPX
VCC5, VCC25, VCC3 or VCCA Less Than Reset
Threshold VRT by More Than 1% (Note 5)
MIN
VOL
Output Voltage Low, RST, COMPX
ISINK = 2.5mA, VCC3 = 3V, VCC5/VCC25 = 0V
ISINK = 100µA, VCC3 = 1V, VCC5/VCC25 = 0V
ISINK = 100µA, VCC3 = 0V, VCC5/VCC25 = 1V
ISINK = 100µA, VCC3 = 1V, VCC5/VCC25 = 1V
●
●
●
●
VOH
Output Voltage High, RST, COMPX (Note 6)
ISOURCE = 1µA
● VCC3 – 1
TYP
MAX
0.15
0.05
0.05
0.05
UNITS
µs
110
0.4
0.3
0.3
0.3
V
V
V
V
V
LTC1727-5/LTC1728-5 Only
VOVR
VCC5 Reset Override Voltage (Note 7)
VCC3 ±0.025
Override VCC5 Ability to Assert RST
V
LTC1728-1.8 The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. VCC3 = 3V, VCC18 = 1.8V, VCCA = VCC3 unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VRT3
Reset Threshold VCC3
VCC3 Input Threshold
●
2.760
2.805
2.850
V
VRT18
Reset Threshold VCC18
VCC18 Input Threshold
●
1.656
1.683
1.710
V
VRTA
Reset Threshold VCCA
VCCA Input Threshold
●
0.985
1.000
1.015
V
VCCOP
VCC3, VCC18 Operating Voltage
RST in Correct Logic State
●
1
7
V
IVCC3
VCC3 Supply Current
VCC18 > VCC3
VCC18 < VCC3, VCC3 = 3V (Note 4)
●
●
1
10
2
20
µA
µA
IVCC18
VCC18 Supply Current
VCC18 < VCC3, VCC18 = 1.8V (Note 4)
●
1
2
µA
IVCCA
VCCA Input Current
VCCA = 1V
●
– 15
0
15
nA
tRST
Reset Pulse Width
RST Low (Note 5)
●
140
200
280
ms
tUV
VCC Undervoltage Detect to RST
VCC18, VCC3 or VCCA Less Than Reset (Note 5)
Threshold VRT by More Than 1%
VOL
Output Voltage Low, RST
ISINK = 2.5mA, VCC3 = 3V, VCC18 = 0V
ISINK = 100µA, VCC3 = 1V, VCC18 = 0V
ISINK = 100µA, VCC3 = 0V, VCC18 = 1V
ISINK = 100µA, VCC3 = 1V, VCC18 = 1V
●
●
●
●
VOH
Output Voltage High, RST
ISOURCE = 1µA (Note 6)
● VCC3 – 1
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: All voltage values are with respect to GND.
Note 3: The LTC1727E/LTC1728E are guaranteed to meet specified
performance from 0°C to 70°C and are designed, characterized and
assured to meet the extended temperature limits of – 40°C to 85°C
but are not tested at these temperatures.
Note 4: Both VCC3 and VCC5/VCC25/VCC18 can act as the supply depending
on which pin has the greatest potential.
µs
110
0.15
0.05
0.05
0.05
0.4
0.3
0.3
0.3
V
V
V
V
V
Note 5: Measured from when input passes through the input threshold
(VRTX) until RST or COMPX passes through 1.5V.
Note 6: The output pins RST and COMPX have internal pull-ups to VCC3 of
typically 6µA. However, external pull-up resistors may be used when faster
rise times are required or for VOH voltages greater than VCC3.
Note 7: The VCC5 reset override voltage is valid for an operating range less
than approximately 4.15V. Above this point the override is turned off and
the VCC5 pin functions normally.
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LTC1727/LTC1728
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TYPICAL PERFOR A CE CHARACTERISTICS
VCCA Threshold Voltage
vs Temperature
VCCA Input Current
vs Input Voltage
1.0
0.5
0
– 0.5
–1.0
–1.5
– 2.0
0.80 0.85 0.90 0.95 1 1.05 1.10 1.15 1.20
INPUT VOLTAGE (V)
TYPICAL TRANSIENT DIRATION (µs)
1.5
1.010
1.005
1.000
0.995
0.990
0.985
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
Reset Pulse Width
vs Temperature
10
260
150
100
50
0
0.1
1
10
100
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VCC)
1727/28 G03
200
160
1.3
4
VOL = 0.2V
20
40
60
80
1.1
1.0
0.9
0.8
2
0.7
1
0.6
0
0
0
100
1
3
4
2
VCC3 OR VCC5 (V)
5
0.5
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
6
1727/28 G05
1727/28 G04
1.5
VCC3 = 3.3V
VCC25 = 2.5V
VCCA = 3.3V
1.4
1.3
15
VCC5 = 5V
VCC3 = 3.3V
VCCA = 3.3V
14
13
1.2
12
1.1
11
IVCC3 (µA)
12
0.9
9
8
7
0.7
7
6
0.6
6
80
100
0.5
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
1727/28 G08
VCC5 = 5V
VCC3 = 3.3V
VCCA = 3.3V
10
0.8
1727/28 G07
4
1.0
8
5
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
100
IVCC5 vs Temperature
(LTC1727-5/LTC1728-5)
11
9
80
1727/28 G06
IVCC3 vs Temperature
(LTC1727-5/LTC1728-5)
IVCC3 vs Temperature
(LTC1727-2.5/LT1728-2.5)
10
VCC3 = 3.3V
VCC25 = 2.5V
VCCA = 3.3V
1.2
5
3
180
1.5
1.4
IVCC25 (µA)
220
IVCC25 vs Temperature
(LTC1727-2.5/LT1728-2.5)
6
TEMPERATURE (°C)
IVCC3 (µA)
200
VOL = 0.4V
7
240
13
250
TA = 25°C
8
ISINK (mA)
RESET PULSE WIDTH, tRST (ms)
9
140
–60 –40 –20
RESET OCCURS
ABOVE CURVE
300
RST, COMPX ISINK
vs Supply Voltage
280
15
100
350
1727/28 G02
1727/28 G01
14
80
TA = 25°C
400
IVCC5 (µA)
INPUT CURRENT (nA)
450
1.015
TA = 25°C
VCCA THRESHOLD VOLTAGE, VRTA (V)
2.0
Typical Transient Duration
vs Comparator Overdrive
5
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
1727/28 G09
LTC1727/LTC1728
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TYPICAL PERFOR A CE CHARACTERISTICS
VCC3 Threshold Voltage
vs Temperature
(All But LTC1728-1.8)
3.125
2.3600
2.3525
2.3450
2.3375
2.3300
2.3225
2.3150
2.3075
2.3000
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
VCC5 Threshold Voltage
vs Temperature
(LTC1727-5/LTC1728-5)
4.750
VCC5 THESHOLD VOLTAGE, VRT5 (V)
3.135
2.3675
VCC3 THRESHOLD VOLTAGE, VRT3 (V)
2.3750
4.725
3.115
3.105
4.700
3.095
3.085
4.675
3.075
4.650
3.065
3.055
4.625
3.045
3.035
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
1727/28 G10
1.5
1.4
100
4.600
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
1727/28 G12
15
VCC3 = 3V
VCC18 = 1.8V
VCCA = 3V
VCC3 = 3V
14 VCC18 = 1.8V
VCCA = 3V
13
1.2
12
1.1
11
1.0
0.9
10
9
0.8
8
0.7
7
0.6
6
0.5
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
5
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
80
100
1727/28 G14
1727/28 G13
VCC3 Threshold Voltage
vs Temperature (LTC1728-1.8)
VCC18 Threshold Voltage
vs Temperature (LTC1728-1.8)
2.845
VCC3 THRESHOLD VOLTAGE, VRT3 (V)
1.710
1.700
1.690
1.680
1.670
1.660
1.650
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
80 100
IVCC3 vs Temperature
(LTC1728-1.8)
IVCC3 (µA)
IVCC18 (µA)
1.3
80
1727/28 G11
IVCC18 vs Temperature
(LTC1728-1.8)
VCC18 THRESHOLD VOLTAGE, VRT18 (V)
VCC25 THRESHOLD VOLTAGE, VRT25 (V)
VCC25 Threshold Voltage
vs Temperature
(LTC1727-2.5/LTC1728-2.5)
80
100
1727/28 G15
2.835
2.825
2.815
2.805
2.795
2.785
2.775
2.765
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
1727/28 G16
5
LTC1727/LTC1728
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PI FU CTIO S
(LTC1727/LTC1728)
VCC3 (Pin 1/Pin 5): 3.3V Sense Input and Power
Supply Pin. (3V Sense Input and Power Supply Pin for
LTC1728-1.8.) This pin provides power to the part
when the voltage on VCC3 is greater than the voltage on
VCC5/VCC25/VCC18. Bypass to ground with a ≥ 0.1µF
ceramic capacitor.
VCC5 (Pin 2/Pin 4): 5V Sense Input and Power Supply
Pin. This pin is used on the LTC1727-5/LTC1728-5 to
provide power to the part when the voltage on VCC5 is
greater than the voltage on VCC3. Bypass to ground with
a ≥ 0.1µF ceramic capacitor.
COMPA (Pin 5): VCCA Comparator Output for the LTC1727.
Active high, open-drain logic output with weak pull-up to
VCC3. Asserted when VCCA is above VRTA. Deasserted
when VCCA is below VRTA or if both the VCC3 and VCC5
supply pins are too low to power the internal bandgap
reference (typically < 2.0V). Can be pulled greater than
VCC3 using an external pull-up.
RST (Pin 6/Pin 1): Reset Logic Output. Active low, opendrain logic output with weak pull-up to VCC3. Can be pulled
up greater than VCC3 when interfacing to 5V logic. Asserted when one or all of the supplies are below trip thresholds and held for 200ms after all supplies become valid.
VCC25 (Pin 2/Pin 4): 2.5V Sense Input and Power Supply
Pin. This pin is used on the LTC1727-2.5/LTC1728-2.5 to
provide power to the part when the voltage on VCC25 is
greater than the voltage on VCC3. Bypass to ground with
a ≥ 0.1µF ceramic capacitor.
COMP5 (Pin 7): VCC5 Comparator Output for the
LTC1727-5. Active high, open-drain logic output with
weak pull-up to VCC3. Asserted when VCC5 is above VRT5.
Can be pulled greater than VCC3 using an external pull-up.
VCC18 (Pin 2/Pin 4): 1.8V Sense Input and Power Supply
Pin. This pin is used on the LTC1728-1.8 to provide
power to the part when the voltage on VCC18 is greater
than the voltage on VCC3. Bypass to ground with a ≥ 0.1µF
ceramic capacitor.
COMP25 (Pin 7): VCC25 Comparator Output for the
LTC1727-2.5. Active high, open-drain logic output with
weak pull-up to VCC3. Asserted when VCC25 is above
VRT25. Can be pulled greater than VCC3 using an external
pull-up.
VCCA (Pin 3/Pin 3): 1V Sense, High Impedance Input. If
unused, it can be tied to either VCC3 or VCC5 /VCC25/VCC18.
COMP3 (Pin 8): VCC3 Comparator Output for the LTC1727.
Active high, open-drain logic output with weak pull-up to
VCC3. Asserted when VCC3 is above VRT3. Can be pulled
greater than VCC3 using an external pull-up.
GND (Pin 4/Pin 2): Ground.
6
LTC1727/LTC1728
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BLOCK DIAGRA S
LTC1727-5/LTC1727-2.5
VCC3
6µA
–
VCC3 1
8 COMP3
+
VCC3
POWER
DETECT
6µA
VCC INTERNAL
VCC5 /
2
VCC25
7
COMP25/
COMP5
–
VCC3
+
6µA
VCCA 3
GND 4
–
+
200ms PULSE GENERATOR
6 RST
200ms
DELAY
VCC3
6µA
5 COMPA
BANDGAP
REFERENCE
1727 BD1
7
LTC1727/LTC1728
W
BLOCK DIAGRA S
LTC1728-5/LTC1728-2.5/LTC1728-1.8
–
VCC3 5
+
POWER
DETECT
VCC INTERNAL
VCC3
VCC5/
VCC25 / 4
VCC18
6µA
–
200ms PULSE GENERATOR
1
200ms
DELAY
+
–
VCCA 3
+
GND 2
BANDGAP
REFERENCE
1727 BD2
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TI I G DIAGRA
VCC Monitor Timing
VCCX
VRTX
tUV
RST
tRST
1.5V
COMPX
1727 TD01
8
RST
LTC1727/LTC1728
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APPLICATIO S I FOR ATIO
Supply Monitoring
Power-Down
The LTC1727 is a low power, high accuracy triple supply
monitoring circuit with three monitor outputs and a
200ms microprocessor reset output.
On power-down, once any of the VCC inputs drop below
its threshold, RST is held at a logic low. A logic low of 0.3V
is guaranteed until both VCC3 and VCC5/VCC25/VCC18 drop
below 1V.
All three VCC inputs must be above predetermined thresholds for reset not to be invoked. The LTC1727/LTC1728
will assert reset during power-up, power-down and brownout conditions on any one or all of the VCC inputs.
Power Detect
The LTC1727/LTC1728 are powered from the 3.3V/3V
input pin (VCC3), the 1.8V input pin (VCC18), the 2.5V
input pin (VCC25) or the 5V input pin (VCC5), whichever
pin has the highest potential. This ensures the part pulls
the RST pin low as soon as either input pin is ≥ 1V.
Power-Up
Upon power-up, either the VCC5 /VCC25/VCC18 or VCC3 pin,
can power the part. This ensures that RST will be low when
either VCC5 /VCC25/VCC18 or VCC3 reaches 1V. As long as
any one of the VCC inputs is below its predetermined
threshold, RST will stay a logic low. Once all of the VCC
inputs rise above their thresholds, an internal timer is
started and RST is released after 200ms.
RST is reasserted whenever any one of the VCC inputs
drops below its predetermined threshold and remains
asserted until 200ms after all of the VCC inputs are above
their thresholds.
On the LTC1727, each of the comparator outputs will be
low until the VCC input that is monitored by that comparator rises above the appropriate predetermined threshold.
The COMP3, and COMP5/COMP25 outputs are guaranteed to be in the correct logic state for either VCC3 or
VCC5/VCC25 greater than 1V. The COMPA output requires
the internal bandgap reference to be valid before the
correct logic state can be output. Therefore, the COMPA
output will be held low until VCCA is above 1V and VCC3 or
VCC5/VCC25 is greater than 2V (typ).
Glitch Immunity
The RST output of the LTC1727/LTC1728 have two forms
of glitch immunity built in. First, the input monitors require
the input voltage to transition at least 10% of the input
threshold (0.1 • VRTH) below the input threshold for
approximately 50µs in order to force the monitor output
low. The duration of the transition must be longer for
voltage transitions of lesser magnitude (see Figure 1).
Secondly, the reset pulse width of approximately 200ms
acts to debounce the RST output ensuring that the RST
output will always be in the correct state.
The individual monitor outputs of the LTC1727 do not
have hysteresis and will track the monitor inputs relative
to the monitor’s input threshold (VRTA, VRT25, VRT3 and
VRT5). A very slow moving input voltage with ripple riding
on it may cause the individual monitor outputs (COMPA,
COMP25, COMP3 and COMP5) to toggle on the ripple as
the input voltage passes the input threshold. The slow
response time of the LTC1727’s input monitors has a
tendency to integrate signals on the inputs improving their
immunity to noise and ripple.
450
400
TRANSIENT DURATION (µs)
The LTC1728 is a low power, high accuracy triple supply
monitoring circuit with a single 200ms microprocessor
reset output.
350
300
250
200
150
100
50
0
1
10
100
0.1
RESET MONITOR OVERDRIVE VOLTAGE (% OF VCC)
1727/28 F01
Figure 1. Transient Duration vs Comparator Overdrive
9
LTC1727/LTC1728
U
W
U
U
APPLICATIO S I FOR ATIO
When monitoring either 3.3V or 5V with VCC3 strapped to
VCC5 (see Figure 2), the part determines which is the
appropriate range. The part handles this situation as
shown in Figure 3. Above 1V and below VRT3, RST is held
low. From VRT3 to approximately 4.15V the part assumes
3.3V supply monitoring and RST is deasserted. Above
approximately 4.15V the part operates as a 5V monitor.
In most systems the 5V supply will pass through the 3.1V
to 4.15V region in < 200ms during power-up, and the
RST output will behave as desired. Table 1 summarizes
the state of RST at various operating voltages with
VCC3 = VCC5.
Override Functions (5V Versions Only)
The VCCA pin, if unused, can be tied to either VCC3 or VCC5.
This is an obvious solution since the trip points for VCC3
and VCC5 will always be greater than the trip point for VCCA.
The VCC5 input trip point is disabled if its voltage is equal
to the voltage on VCC3 ±25mV and the voltage on VCC5 is
less than 4.15V. In this manner, the LTC1727-5/
LTC1728-5 will behave as a 3.3V monitor and VCC5 reset
capability will be disabled.
The VCC5 trip point is reenabled when the voltage on VCC5
is equal to the voltage on VCC3 ±25mV and the two inputs
are greater than approximately 4.15V. In this manner, the
part can function as a 5V monitor with the 3.3V monitor
disabled.
VCC
3.3V OR 5V
Table 1. Override Truth Table (VCC3 = VCC5)
INPUTS (VCC3 = VCC5 = VCC)
—
1V ≤ VCC ≤ VRT3
0
VRT3 ≤ VCC ≤ 4.15V
1
4.15V ≤ VCC ≤ VRT5
0
VRT5 ≤ VCC
1
LTC1728-5
5
4
3
2
R1
10k
VCC3
VCC5
VCCA
RST
1
TO SYSTEM
RESET
GND
1727/28 F02
Figure 2. Single Supply Monitor with Others Disabled
5
RST OUTPUT VOLTAGE (V)
VCC3 = VCC5 = VCCA = 0V TO 5V
10k PULL-UP FROM RST TO VCC3
4
3
2
1
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
5
1727/28 F03
Figure 3. RST Voltage vs Supply Voltage
10
RST
0V ≤ VCC ≤ 1V
LTC1727/LTC1728
U
W
U
U
APPLICATIO S I FOR ATIO
Figure 4 contains a simple circuit for 5V systems that can’t
risk the RST output going high in the 3.1V to 4.15V range
(possibly due to very slow rise time on the 5V supply).
Diode D1 powers the LTC1728-5 while dropping ≈ 0.6V
from the VCC5 pin to the VCC3 pin. This prevents the part’s
internal override circuit from being activated. Without the
override circuit active, the RST pin stays low until VCC5
reaches VRT5 ≅ 4.675V. (See Figure 5.)
LTC1727-2.5/LTC1728-2.5/LTC1728-1.8
Override Functions
The VCCA pin, if unused, can be tied to either VCC3 or VCC25/
VCC18. This is an obvious solution since the trip points for
VCC3 and VCC25/VCC18 will always be greater than the trip
point for VCCA. Likewise, the VCC25/VCC18, if unused, can
be tied to VCC3. VCC3 must always be used. Tying VCC3 to
VCC25/VCC18 and operating off of a 2.5V/1.8V supply will
result in the continuous assertion of RST.
5V
D1
LTC1728-5
5
4
3
2
0.1µF
R1
10k
VCC3
VCC5
VCCA
RST
1
TO SYSTEM
RESET
GND
D1: MMBD914 OR EQUIVALENT
1727/28 F04
Figure 4. LTC1728-5 Monitoring a Single 5V
Supply. D1 Used to Avoid RST High Near 3.1V
to 4V (See Figure 3).
RST OUTPUT VOLTAGE (V)
5
VCC5 = VCCA = 0V TO 5V
10k PULL-UP FROM RST TO VCC5
TA = 25°C
4
3
2
1
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
VCC5 (V)
1727/28 F05
Figure 5. RST Output Voltage
Characteristics of the Circuit in Figure 4
11
LTC1727/LTC1728
U
TYPICAL APPLICATIO S
Triple Supply Monitor (3.3V, 5V and Adjustable)
LTC1728-5
3.3V
ADJUSTABLE SUPPLY
OR DC/DC FEEDBACK
DIVIDER
R1*
5V
5
4
3
R2*
2
VCC3
RST
1
SYSTEM RESET
VCC5
VCCA
GND
1727/28 TA03
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Dual Supply Monitor (3.3V and 5V, Defeat VCCA Input)
LTC1728-5
5
3.3V
4
5V
3
2
VCC3
RST
1
SYSTEM RESET
VCC5
VCCA
GND
1727/28 TA04
Dual Supply Monitor (3.3V or 5V Plus Adjustable)
3.3V OR
5V
LTC1728-5
5
4
ADJUSTABLE
SUPPLY
R1*
3
R2*
2
VCC3
RST
10k
1
SYSTEM RESET
VCC5
VCCA
GND
1727/28 TA05
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
REFER TO LTC1728-5 OVERRIDE FUNCTIONS IN
THE APPLICATIONS INFORMATION SECTION
12
LTC1727/LTC1728
U
TYPICAL APPLICATIO S
Dual Supply Monitor (3.3V Plus Adjustable)
3.3V
LTC1728-2.5
5
4
ADJUSTABLE
SUPPLY
R1*
3
2
R2*
VCC3
RST
10k
1
SYSTEM RESET
VCC25
VCCA
GND
1727/28 TA06
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Using VCCA Tied to DC/DC Feedback Divider
2.9V
LTC1435
VOSENSE
ADJUSTABLE
RESET TRIP
THRESHOLD 2.74V
6
35.7k
1%
3.3V
2.8k
5V
1%
22.1k
1%
LTC1728-5
5
4
3
2
VCC3
RST
1
SYSTEM RESET
VCC5
VCCA
GND
1727/28 TA07
13
LTC1727/LTC1728
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8
7 6
5
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
1
2 3
4
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.034 ± 0.004
(0.86 ± 0.102)
0° – 6° TYP
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
BSC
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1098
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
2.60 – 3.00
(0.102 – 0.118)
1.50 – 1.75
(0.059 – 0.069)
0.35 – 0.55
(0.014 – 0.022)
1.90
(0.074)
REF
0.00 – 0.15
(0.00 – 0.006)
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
0.90 – 1.45
(0.035 – 0.057)
0.35 – 0.50
0.90 – 1.30
(0.014 – 0.020)
(0.035 – 0.051)
FIVE PLACES (NOTE 2)
S5 SOT-23 0599
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
14
0.95
(0.037)
REF
LTC1727/LTC1728
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SO8 1298
15
LTC1727/LTC1728
U
TYPICAL APPLICATIO
Triple Supply Monitor with Manual Reset Button
12V (± 5%)
VTRIP = 11.2V
(± 0.17V)
5V
3.3V
5
100nF
R3*
10k
5%
R1
1.07M
0.1%
RST
1
LTC1728-5
4
VCC5
100nF
R2
105k
0.1%
MANUAL
RESET BUTTON
(NORMALLY OPEN)
VCC3
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
3
VCCA
GND
2
1727/28 TA02
V
VTRIP = CCA (R1 + R2)
R2
V
R1 = R2 TRIP – 1
VCCA
(
)
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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4.65V Threshold
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3.3V Supply Monitor, Watchdog Timer and Battery Backup
2.9V Threshold
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4.65V Threshold
LTC1232
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4.37V/4.62V Threshold
LTC1326
Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ
4.725V, 3.118V, 1V Thresholds (±0.75%)
LTC1326-2.5
Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ
2.363V, 3.118V, 1V Thresholds (±0.75%)
LTC1443/LTC1444
LTC1445
Micropower Quad Comparators with 1% Reference
LTC1443 Has 1.182V Reference, LTC1444/LTC1445
Have 1.221V Reference and Adjustable Hysteresis
LTC1536
Precision Triple Supply Monitor for PCI Applications
Meets PCI tFAIL Timing Specifications
LTC1540
Nanopower Comparator with 2% Reference
1.182V Reference, 300nA Supply Current, 8-Pin MSOP
LTC1726-2.5
Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ
Adjustable RESET and Watchdog Time Outs
LTC1726-5
Micropower Triple Supply Monitor for 5V, 3.3V and ADJ
Adjustable RESET and Watchdog Time Outs
LTC1985-1.8
Micropower Triple Supply Monitor for 3.3V, 1.8V and ADJ
Push-Pull RESET Output, SOT-23
16
Linear Technology Corporation
17278f LT/TP 0400 4K • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1999
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