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LTC1727/LTC1728 Micropower Precision Triple Supply Monitors in 8-Lead MSOP and 5-Lead SOT-23 Packages
FEATURES
s
DESCRIPTIO
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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 LTC1728-3.3: 3.3V, 1.8V and ADJ 1.5% Threshold Accuracy Over Temperature Very Low Supply Current: 10A 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
The LTC(R)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. 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 (10A 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s s s s s
Desktop Computers Notebook Computers Intelligent Instruments Portable Battery-Powered Equipment Network Servers
TYPICAL APPLICATIO
DC/DC CONVERTER 3.3V 5V 1.8V
SYSTEM LOGIC
Triple Supply Monitor with Power Good Output (3.3V, 2.5V and Adjustable)
LTC1727-2.5 3.3V 2.5V 1 2 3 R2 4 VCC3 COMP3 8 7 6 5
1727/28 TA08
5
VCC3
RST
1
LTC1728-5 4 0.1F 0.1F R1 61.9k 1% 3 R2 100k 1% VCC5 2
VCCA
GND
1727/28 TA01
ADJUSTABLE SUPPLY
R1
U
R3 10k R4 10k POWER GOOD SYSTEM RESET VCC25 COMP25 VCCA GND RST COMPA
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U
U
1
LTC1727/LTC1728 ABSOLUTE AXI U RATI GS (Notes 1, 2)
Operating Temperature Range (Note 3) ............................................. - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................ 300C 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
PACKAGE/ORDER I FOR ATIO
TOP VIEW VCC3 VCC5 /VCC25 VCCA GND 1 2 3 4 8 7 6 5 COMP3 COMP25/COMP5 RST COMPA
VCC3 1 VCC5/ 2 VCC25 VCCA 3 GND 4
MS8 PACKAGE 8-LEAD PLASTIC MSOP
TJMAX = 125C, JA = 200C/W
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 125C, JA = 150C/W
ORDER PART NUMBER LTC1727EMS8-2.5 LTC1727EMS8-5
MS8 PART MARKING LTHY LTHX
ORDER PART NUMBER LTC1727ES8-2.5 LTC1727IS8-2.5 LTC1727ES8-5 LTC1727IS8-5
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL VRT3 VRT5 VRT25 VRTA VCCOP VCCOPA IVCC3 IVCC25 IVCC5 IVCCA tRST tUV PARAMETER Reset Threshold VCC3 Reset Threshold VCC5 Reset Threshold VCC25 Reset Threshold VCCA VCC3, VCC5/VCC25 Operating Voltage VCC3, VCC5/VCC25 Operating Voltage VCC3 Supply Current VCC25 Supply Current VCC5 Supply Current VCCA Input Current Reset Pulse Width VCC Undervoltage Detect to RST or COMPX
All except LTC1728-1.8/LTC1728-3.3. The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless otherwise noted.
CONDITIONS VCC3 Input Threshold VCC5 Input Threshold (5V Version) VCC25 Input Threshold (2.5V Version) VCCA Input Threshold RST, COMP3, COMP5, COMP25 in Correct Logic State Minimum Supply Voltage to Guarantee COMPA in Correct Logic State VCC5/VCC25 > VCC3 VCC5/VCC25 < VCC3, VCC3 = 3.3V (Note 4) VCC25 < VCC3, VCC25 = 2.5V (Note 4) VCC5 = 5V, VCC3 < VCC5 VCCA = 1V RST Low with 10k Pull-Up to VCC3 (Note 5) VCC5, VCC25, VCC3 or VCCA Less Than Reset Threshold VRT by More Than 1% (Note 5)
q q q q q q q q q q q q
2
U
U
W
WW
U
W
TOP VIEW
TOP VIEW
8 7 6 5
COMP3 COMP25/ COMP5 RST COMPA
RST 1 GND 2 VCCA 3
5 VCC3 VCC5/ 4 VCC25 / VCC18
S5 PACKAGE 5-LEAD PLASTIC SOT-23
TJMAX = 125C, JA = 250C/W
S8 PART MARKING 172725 727I25 17275 1727I5
ORDER PART NUMBER LTC1728ES5-1.8 LTC1728ES5-2.5 LTC1728ES5-3.3 LTC1728ES5-5
S5 PART MARKING LTPH LTIA LTYP LTHZ
MIN 3.036 4.600 2.300 0.985 1
TYP 3.086 4.675 2.338 1.000 2 1 10 1 10
MAX 3.135 4.750 2.375 1.015 7 2.3 2 20 2 20 15 280
UNITS V V V V V V A A A A nA ms s
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- 15 140
0 200 110
LTC1727/LTC1728
ELECTRICAL CHARACTERISTICS
SYMBOL VOL PARAMETER Output Voltage Low, RST, COMPX
All except LTC1728-1.8/LTC1728-3.3. The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless otherwise noted.
CONDITIONS ISINK = 2.5mA, VCC3 = 3V, VCC5/VCC25 = 0V ISINK = 100A, VCC3 = 1V, VCC5/VCC25 = 0V ISINK = 100A, VCC3 = 0V, VCC5/VCC25 = 1V ISINK = 100A, VCC3 = 1V, VCC5/VCC25 = 1V ISOURCE = 1A Override VCC5 Ability to Assert RST
q q q q q VCC3 - 1
MIN
TYP 0.15 0.05 0.05 0.05
MAX 0.4 0.3 0.3 0.3
UNITS V V V V V
VOH VOVR
Output Voltage High, RST, COMPX (Note 6) VCC5 Reset Override Voltage (Note 7)
LTC1727-5/LTC1728-5 Only VCC3 0.025 V
LTC1728-1.8 The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC3 = 3V, VCC18 = 1.8V, VCCA = VCC3 unless otherwise noted.
SYMBOL VRT3 VRT18 VRTA VCCOP IVCC3 IVCC18 IVCCA tRST tUV VOL PARAMETER Reset Threshold VCC3 Reset Threshold VCC18 Reset Threshold VCCA VCC3, VCC18 Operating Voltage VCC3 Supply Current VCC18 Supply Current VCCA Input Current Reset Pulse Width VCC Undervoltage Detect to RST Output Voltage Low, RST CONDITIONS VCC3 Input Threshold VCC18 Input Threshold VCCA Input Threshold RST in Correct Logic State VCC18 > VCC3 VCC18 < VCC3, VCC3 = 3V (Note 4) VCC18 < VCC3, VCC18 = 1.8V (Note 4) VCCA = 1V RST Low (Note 5) VCC18, VCC3 or VCCA Less Than Reset (Note 5) Threshold VRT by More Than 1% ISINK = 2.5mA, VCC3 = 3V, VCC18 = 0V ISINK = 100A, VCC3 = 1V, VCC18 = 0V ISINK = 100A, VCC3 = 0V, VCC18 = 1V ISINK = 100A, VCC3 = 1V, VCC18 = 1V ISOURCE = 1A (Note 6)
q q q q q VCC3 - 1 q q q q q q q q q
MIN 2.760 1.656 0.985 1
TYP 2.805 1.683 1.000 1 10 1
MAX 2.850 1.710 1.015 7 2 20 2 15 280
UNITS V V V V A A A nA ms s
- 15 140
0 200 110 0.15 0.05 0.05 0.05
0.4 0.3 0.3 0.3
V V V V V
VOH
Output Voltage High, RST
LTC1728-3.3 The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC3 = 3.3V, VCC18 = 1.8V, VCCA = VCC3 unless otherwise noted.
SYMBOL VRT3 VRT18 VRTA VCCOP IVCC3 IVCC18 IVCCA tRST tUV VOL PARAMETER Reset Threshold VCC3 Reset Threshold VCC18 Reset Threshold VCCA VCC3, VCC18 Operating Voltage VCC3 Supply Current VCC18 Supply Current VCCA Input Current Reset Pulse Width VCC Undervoltage Detect to RST Output Voltage Low, RST CONDITIONS VCC3 Input Threshold VCC18 Input Threshold VCCA Input Threshold RST in Correct Logic State VCC18 > VCC3 VCC18 < VCC3, VCC3 = 3.3V (Note 4) VCC18 < VCC3, VCC18 = 1.8V (Note 4) VCCA = 1V RST Low (Note 5) VCC18, VCC3 or VCCA Less Than Reset (Note 5) Threshold VRT by More Than 1% ISINK = 2.5mA, VCC3 = 3.3V, VCC18 = 0V ISINK = 100A, VCC3 = 1V, VCC18 = 0V ISINK = 100A, VCC3 = 0V, VCC18 = 1V ISINK = 100A, VCC3 = 1V, VCC18 = 1V ISOURCE = 1A (Note 6)
q q q q q q q q q
MIN 3.036 1.656 0.985 1
TYP 3.086 1.683 1.000 1 10 1
MAX 3.135 1.710 1.015 7 2 20 2 15 280
UNITS V V V V A A A nA ms s
- 15 140
0 200 110
q q q q q VCC3 - 1
0.15 0.05 0.05 0.05
0.4 0.3 0.3 0.3
VOH
Output Voltage High, RST
V V V V V
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LTC1727/LTC1728
ELECTRICAL CHARACTERISTICS
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 0C to 70C and are designed, characterized and assured to meet the extended temperature limits of - 40C to 85C 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. 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 6A. 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.
TYPICAL PERFOR A CE CHARACTERISTICS
VCCA Input Current vs Input Voltage
2.0 1.5
INPUT CURRENT (nA)
VCCA THRESHOLD VOLTAGE, VRTA (V)
TA = 25C
1.010 1.005 1.000 0.995 0.990 0.985 -60 -40 -20 0 20 40 60 TEMPERATURE (C)
TYPICAL TRANSIENT DIRATION (s)
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)
1727/28 G01
Reset Pulse Width vs Temperature
280
RESET PULSE WIDTH, tRST (ms)
260 240 220 200 180 160 140 -60 -40 -20
IVCC25 (A)
ISINK (mA)
0
20
40
60
TEMPERATURE (C)
1727/28 G04
4
UW
80
VCCA Threshold Voltage vs Temperature
1.015
Typical Transient Duration vs Comparator Overdrive
450 400 350 300 250 200 150 100 50 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VCC)
1727/28 G03
TA = 25C
RESET OCCURS ABOVE CURVE
80
100
1727/28 G02
RST, COMPX ISINK vs Supply Voltage
10 9 8 7 6 5 4 3 2 1 0
100
IVCC25 vs Temperature (LTC1727-2.5/LT1728-2.5)
1.5 1.4 VCC3 = 3.3V VCC25 = 2.5V VCCA = 3.3V
TA = 25C
VOL = 0.4V
1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6
VOL = 0.2V
0
1
3 4 2 VCC3 OR VCC5 (V)
5
6
0.5 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C)
80
100
1727/28 G05
1727/28 G06
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LTC1727/LTC1728 TYPICAL PERFOR A CE CHARACTERISTICS
IVCC3 vs Temperature (LTC1727-2.5/ LTC1728-2.5/LTC1728-3.3)
15 14 13 12
IVCC3 (A)
VCC3 = 3.3V VCC25 = 2.5V VCCA = 3.3V
IVCC3 (A)
IVCC5 (A)
11 10 9 8 7 6 5 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100
VCC25 Threshold Voltage vs Temperature (LTC1727-2.5/LTC1728-2.5)
2.3750 VCC25 THRESHOLD VOLTAGE, VRT25 (V) VCC3 THRESHOLD VOLTAGE, VRT3 (V) 2.3675 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 3.135 3.125 3.115 3.105 3.095 3.085 3.075 3.065 3.055 3.045
3.035 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C)
80
100
VCC5 THESHOLD VOLTAGE, VRT5 (V)
IVCC18 vs Temperature (LTC1728-1.8/LTC1728-3.3)
1.5 1.4 1.3 1.2 VCC3 = 3V VCC18 = 1.8V VCCA = 3V
IVCC18 (A)
IVCC3 (A)
1.1 1.0 0.9 0.8 0.7 0.6 0.5 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100
UW
1727/28 G07
IVCC3 vs Temperature (LTC1727-5/LTC1728-5)
1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100 15 VCC5 = 5V VCC3 = 3.3V VCCA = 3.3V 14 13 12 11 10 9 8 7 6
IVCC5 vs Temperature (LTC1727-5/LTC1728-5)
VCC5 = 5V VCC3 = 3.3V VCCA = 3.3V
5 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C)
80
100
1727/28 G08
1727/28 G09
VCC3 Threshold Voltage vs Temperature (All But LTC1728-1.8)
4.750 4.725 4.700 4.675 4.650 4.625
VCC5 Threshold Voltage vs Temperature (LTC1727-5/LTC1728-5)
4.600 20 40 60 -60 -40 -20 0 TEMPERATURE (C)
80 100
1727/28 G12
1727/28 G10
1727/28 G11
IVCC3 vs Temperature (LTC1728-1.8)
15 VCC3 = 3V 14 VCC18 = 1.8V VCCA = 3V 13 12 11 10 9 8 7 6 5 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100
1727/28 G13
1727/28 G14
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LTC1727/LTC1728 TYPICAL PERFOR A CE CHARACTERISTICS
VCC18 Threshold Voltage vs Temperature (LTC1728-1.8/LTC1728-3.3)
1.710
VCC18 THRESHOLD VOLTAGE, VRT18 (V) VCC3 THRESHOLD VOLTAGE, VRT3 (V) 2.845 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
1.700 1.690 1.680 1.670 1.660 1.650 -60 -40 -20 0 20 40 60 TEMPERATURE (C)
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 0.1F 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 0.1F ceramic capacitor. 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 0.1F ceramic capacitor. VCC18 (Pin 2/Pin 4): 1.8V Sense Input and Power Supply Pin. This pin is used on the LTC1728-1.8/LTC1728-3.3 to provide power to the part when the voltage on VCC18 is greater than the voltage on VCC3. Bypass to ground with a 0.1F ceramic capacitor.
6
UW
VCC3 Threshold Voltage vs Temperature (LTC1728-1.8)
80
100
1727/28 G15
1727/28 G16
U
U
U
VCCA (Pin 3/Pin 3): 1V Sense, High Impedance Input. If unused, it can be tied to either VCC3 or VCC5 /VCC25/VCC18. GND (Pin 4/Pin 2): Ground. 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. 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.
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LTC1727/LTC1728
PI FU CTIO S
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.
BLOCK DIAGRA S
LTC1727-5/LTC1727-2.5
VCC3 6A
VCC3 1
POWER DETECT VCC5 / 2 VCC25
VCC INTERNAL
VCCA 3
GND 4
+
+
+
-
-
-
W
U
U
U
(LTC1727/LTC1728)
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.
8 COMP3
VCC3 6A
7
COMP25/ COMP5
VCC3 6A
200ms PULSE GENERATOR 200ms DELAY VCC3 6A
6 RST
5 COMPA BANDGAP REFERENCE
1727 BD1
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LTC1727/LTC1728
BLOCK DIAGRA S
LTC1728-5/LTC1728-2.5/LTC1728-1.8/LTC1728-3.3
VCC3 5
POWER DETECT VCC5/ VCC25 / 4 VCC18
VCC INTERNAL VCC3 6A
VCCA 3
GND 2
TI I G DIAGRA
VCCX
VRTX tUV tRST 1.5V
RST
COMPX
1727 TD01
8
+
+
+
-
-
-
W
W
200ms PULSE GENERATOR 200ms DELAY
1
RST
BANDGAP REFERENCE
1727 BD2
UW
VCC Monitor Timing
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LTC1727/LTC1728
APPLICATIO S I FOR ATIO
Supply Monitoring
The LTC1727 is a low power, high accuracy triple supply monitoring circuit with three monitor outputs and a 200ms microprocessor reset output. The LTC1728 is a low power, high accuracy triple supply monitoring circuit with a single 200ms microprocessor reset output. 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).
TRANSIENT DURATION (s)
U
Power-Down 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. 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 50s 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.
450 400 350 300 250 200 150 100 50 0 1 10 100 0.1 RESET MONITOR OVERDRIVE VOLTAGE (% OF VCC)
1727/28 F01
W
U
U
Figure 1. Transient Duration vs Comparator Overdrive
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LTC1727/LTC1728
APPLICATIO S I FOR ATIO
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 5 4 3 2
Figure 2. Single Supply Monitor with Others Disabled
5 VCC3 = VCC5 = VCCA = 0V TO 5V 10k PULL-UP FROM RST TO VCC3
RST OUTPUT VOLTAGE (V)
4
3
2
1
0
0
Figure 3. RST Voltage vs Supply Voltage
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10
U
LTC1728-5 VCC3 VCC5 VCCA GND
W
U
U
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.
Table 1. Override Truth Table (VCC3 = VCC5)
INPUTS (VCC3 = VCC5 = VCC) 0V VCC 1V 1V VCC VRT3 VRT3 VCC 4.15V 4.15V VCC VRT5 VRT5 VCC RST -- 0 1 0 1
R1 10k RST 1 TO SYSTEM RESET
1727/28 F02
1
3 4 2 SUPPLY VOLTAGE (V)
5
1727/28 F03
LTC1727/LTC1728
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.)
5V D1 LTC1728-5 5 4 3 2 0.1F VCC3 VCC5 VCCA 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).
5 VCC5 = VCCA = 0V TO 5V 10k PULL-UP FROM RST TO VCC5 TA = 25C
RST OUTPUT VOLTAGE (V)
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
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LTC1727-2.5/LTC1728-2.5/LTC1728-1.8/LTC1728-3.3 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.
R1 10k RST 1 TO SYSTEM RESET
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LTC1727/LTC1728
TYPICAL APPLICATIO S
Triple Supply Monitor (3.3V, 5V and Adjustable)
ADJUSTABLE SUPPLY OR DC/DC FEEDBACK DIVIDER
ADJUSTABLE SUPPLY
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LTC1728-5 3.3V R1* 5V 5 4 3 R2* 2 VCC3 VCC5 VCCA GND
1727/28 TA03
RST
1
SYSTEM RESET
*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 3.3V 5V 5 4 3 2 VCC3 VCC5 VCCA GND
1727/28 TA04
RST
1
SYSTEM RESET
Dual Supply Monitor (3.3V or 5V Plus Adjustable)
3.3V OR 5V 5 4 R1* R2* 3 2
LTC1728-5 VCC3 VCC5 VCCA GND RST 1
10k SYSTEM RESET
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
17278fa
LTC1727/LTC1728
TYPICAL APPLICATIO S
Dual Supply Monitor (3.3V Plus Adjustable)
ADJUSTABLE SUPPLY
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3.3V LTC1728-2.5 5 4 R1* R2* 3 2 VCC3 VCC25 VCCA GND
1727/28 TA06
10k 1 SYSTEM RESET
RST
*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 6 35.7k 1% 3.3V 2.8k 5V 1% 22.1k 1% LTC1728-5 5 4 3 2 VCC3 VCC5 VCCA GND
1727/28 TA07
RST
1
SYSTEM RESET
ADJUSTABLE RESET TRIP THRESHOLD 2.74V
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LTC1727/LTC1728
PACKAGE DESCRIPTIO
0.889 0.127 (.035 .005)
5.23 (.206) MIN
3.2 - 3.45 (.126 - .136) DETAIL "A"
0.42 0.04 (.0165 .0015) TYP
0.65 (.0256) BSC
RECOMMENDED SOLDER PAD LAYOUT
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
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
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
0.016 - 0.050 (0.406 - 1.270)
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MS8 Package 8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
3.00 0.102 (.118 .004) (NOTE 3) 0.52 (.206) REF 8 7 65 0.254 (.010) GAUGE PLANE 0.53 0.015 (.021 .006) 1 1.10 (.043) MAX 23 4 0.86 (.34) REF DETAIL "A" 0 - 6 TYP 4.88 0.1 (.192 .004) 3.00 0.102 (.118 .004) NOTE 4 0.18 (.077) SEATING PLANE 0.22 - 0.38 (.009 - .015) 0.13 0.05 (.005 .002)
MSOP (MS8) 1001
0.65 (.0256) BCS
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
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.050 (1.270) BSC
SO8 1298
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LTC1727/LTC1728
PACKAGE DESCRIPTIO
A A1 A2 L
SOT-23 (Original) .90 - 1.45 (.035 - .057) .00 - .15 (.00 - .006) .90 - 1.30 (.035 - .051) .35 - .55 (.014 - .021)
SOT-23 (ThinSOT) 1.00 MAX (.039 MAX) .01 - .10 (.0004 - .004) .80 - .90 (.031 - .035) .30 - .50 REF (.012 - .019 REF) PIN ONE .95 (.037) REF .25 - .50 (.010 - .020) (5PLCS, NOTE 2) 2.60 - 3.00 (.102 - .118) 1.50 - 1.75 (.059 - .069) (NOTE 3)
.20 (.008) DATUM `A' A A2
L NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES)
3. DRAWING NOT TO SCALE 4. DIMENSIONS ARE INCLUSIVE OF PLATING 5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 6. MOLD FLASH SHALL NOT EXCEED .254mm 7. PACKAGE EIAJ REFERENCE IS: SC-74A (EIAJ) FOR ORIGINAL JEDEC MO-193 FOR THIN
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.
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S5 Package 5-Lead Plastic SOT-23
(Reference LTC DWG # 05-08-1633) (Reference LTC DWG # 05-08-1635)
2.80 - 3.10 (.110 - .118) (NOTE 3) .09 - .20 (.004 - .008) (NOTE 2) 1.90 (.074) REF A1
S5 SOT-23 0401
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LTC1727/LTC1728
TYPICAL APPLICATIO
MANUAL RESET BUTTON (NORMALLY OPEN)
RELATED PARTS
PART NUMBER LTC690 LTC694-3.3 LTC699 LTC1232 LTC1326 LTC1326-2.5 LTC1443/LTC1444 LTC1445 LTC1536 LTC1540 LTC1726-2.5 LTC1726-5 LTC1985-1.8 DESCRIPTION 5V Supply Monitor, Watchdog Timer and Battery Backup 3.3V Supply Monitor, Watchdog Timer and Battery Backup 5V Supply Monitor and Watchdog Timer 5V Supply Monitor, Watchdog Timer and Push-Button Reset Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ Micropower Quad Comparators with 1% Reference Precision Triple Supply Monitor for PCI Applications Nanopower Comparator with 2% Reference Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ Micropower Triple Supply Monitor for 5V, 3.3V and ADJ Micropower Triple Supply Monitor for 3.3V, 1.8V and ADJ COMMENTS 4.65V Threshold 2.9V Threshold 4.65V Threshold 4.37V/4.62V Threshold 4.725V, 3.118V, 1V Thresholds (0.75%) 2.363V, 3.118V, 1V Thresholds (0.75%) LTC1443 Has 1.182V Reference, LTC1444/LTC1445 Have 1.221V Reference and Adjustable Hysteresis Meets PCI tFAIL Timing Specifications 1.182V Reference, 300nA Supply Current, 8-Pin MSOP Adjustable RESET and Watchdog Time Outs Adjustable RESET and Watchdog Time Outs Push-Pull RESET Output, SOT-23
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
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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% R2 105k 0.1% 4 100nF 3 VCCA GND
1727/28 TA02
VCC3
RST
1
LTC1728-5 VCC5 2
*OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE
V VTRIP = CCA (R1 + R2) R2 V R1 = R2 TRIP - 1 VCCA
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17278fa LT/TP 1101 1.5K REV A * PRINTED IN THE USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 1999

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