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Final Electrical Specifications
LTC2900 Programmable Quad Supply Monitor with Adjustable Reset Timer
June 2002
FEATURES
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DESCRIPTIO
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Simultaneously Monitors Four Supplies 16 User Selectable Combinations of 5V, 3.3V, 3V, 2.5V, 1.8V, 1.5V and/or Adjustable Voltage Thresholds Guaranteed Threshold Accuracy: 1.5% of Monitored Voltage Over Temperature Low Supply Current: 43A Typ Adjustable Reset Time Small MS10 Package Manual Reset Pin Open-Drain RST Output (LTC2900-1) Push-Pull RST Output (LTC2900-2) Power Supply Glitch Immunity Guaranteed RST for VCC 1V
The LTC(R)2900 is a programmable supply monitor for systems with up to four supply voltages. One of 16 preset or adjustable voltage monitor combinations can be selected using an external resistor divider connected to the program pin. The preset voltage thresholds are accurate to 1.5% over temperature. The reset delay time is adjustable using an external capacitor and the manual reset input may be used with a momentary switch to issue reset pulses with programmed duration. Tight voltage threshold accuracy and glitch immunity ensure reliable reset operation without false triggering. The RST output is guaranteed to be in the correct state for VCC down to 1V. The LTC2900-1 features an open-drain RST output, while the LTC2900-2 has a push-pull RST output. The 43A supply current makes the LTC2900 ideal for power conscious systems and it may be configured to monitor less than four inputs. The parts are available in the 10-lead MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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Desktop and Notebook Computers Multivoltage Systems Telecom Equipment Portable Battery-Powered Equipment Network Servers
TYPICAL APPLICATIO
Quad Supply Monitor (5V, 3.3V, 2.5V, 1.8V)
5V 3.3V DC/DC CONVERTER 2.5V 1.8V 1 2 9 V3 V4 V1 LTC2900-2 10 V2 8 7 VREF VPG GND 6 4 RST PBR CRT 3 CRT 47nF 5 PUSH-BUTTON RESET
2900 TA01
C1 0.1F
C2 0.1F R1 59k 1% R2 40.2k 1%
tRST = 216ms
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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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SYSTEM LOGIC
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LTC2900
ABSOLUTE
(Notes 1, 2, 3)
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RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW V3 V1 CRT RST PBR 1 2 3 4 5 10 9 8 7 6 V2 V4 VREF VPG GND
V1, V2, V3, V4, VPG ..................................... - 0.3V to 7V RST (LTC2900-1)........................................ - 0.3V to 7V RST (LTC2900-2).......................... - 0.3V to (V2 + 0.3V) CRT, PBR ..................................... - 0.3V to (VCC + 0.3V) VREF ............................................. - 0.3V to (VCC + 0.3V) Reference Load Current (IVREF) ............................ 1mA V4 Input Current (- ADJ Mode) ............................ - 1mA Operating Temperature Range LTC2900-1C/LTC2900-2C ....................... 0C to 70C LTC2900-1I/LTC2900-2I .................... -40C to 85C Storage Temperature Range .................. - 65C to 150C Lead Temperature (Soldering, 10 sec)................... 300C
LTC2900-1CMS LTC2900-2CMS LTC2900-1IMS LTC2900-2IMS MS10 PART MARKING LTYJ LTYL LTYK LTYM
MS10 PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125C, JA = 250C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL VRT50 VRT33 VRT30 VRT25 VRT18 VRT15 VRTA VRTAN VCC VCCMINP VREF VPG IVPG IV1 IV2 IV3 IV4 PARAMETER 5V, 5% Reset Threshold 3.3V, 5% Reset Threshold 3V, 5% Reset Threshold 2.5V, 5% Reset Threshold 1.8V, 5% Reset Threshold 1.5V, 5% Reset Threshold ADJ Reset Threshold - ADJ Reset Threshold Minimum Internal Operating Voltage Minimum Required for Programming Reference Voltage Programming Voltage Range VPG Input Current V1 Input Current V2 Input Current V3 Input Current V4 Input Current
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, unless otherwise noted. (Note 3)
CONDITIONS V1 Input Threshold V1, V2 Input Threshold V2 Input Threshold V2, V3 Input Threshold V3, V4 Input Threshold V3, V4 Input Threshold V3, V4 Input Threshold V4 Input Threshold RST in Correct Logic State, VCC Rising Prior to Program VCC Rising VCC 2.3V, IVREF = 1mA, CREF 1000pF VCC VCCMINP VPG = VREF V1 = 5V, IVREF = 12A, (Note 4) V2 = 3.3V V3 = 2.5V V3 = 0.55V (ADJ Mode) V4 = 1.8V V4 = 0.55V (ADJ Mode) V4 = -0.05V (-ADJ Mode) VCRT = 0V VCRT = 1.3V CRT = 1500pF
q q q q q q q q q q q q q q q q q q q q q q q
MIN 4.600 3.036 2.760 2.300 1.656 1.380 0.492 - 18
TYP 4.675 3.086 2.805 2.338 1.683 1.403 0.500 0
MAX 4.750 3.135 2.850 2.375 1.710 1.425 0.508 18 1 2.42
UNITS V V V V V V V mV V V V V nA A A A nA A nA nA A A ms
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1.192 0
1.210
1.228 VREF 20
43 0.8 0.52 -15 0.34 -15 -1.4 10 4.9 -2 20 6.9
75 2 1.2 15 0.8 15 15 -2.6 30 8.9
ICRT(UP) ICRT(DN) tRST
CRT Pull-Up Current CRT Pull-Down Current Reset Time-Out Period
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LTC2900
ELECTRICAL CHARACTERISTICS
SYMBOL tUV VOL PARAMETER VX Undervoltage Detect to RST Output Voltage Low RST
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, unless otherwise noted. (Note 3)
CONDITIONS VX Less Than Reset Threshold VRTX by More Than 1% ISINK = 2.5mA; V1 = 3V, V2 = 3V; V3, V4 = 0V; VPG = 0V ISINK = 100A; V2 = 1V; V1, V3, V4 = 0V ISINK = 100A; V1 = 1V; V2, V3, V4 = 0V VOH Output Voltage High RST (LTC2900-1) (Note 5) Output Voltage High RST (LTC2900-2) (Note 6) Manual Reset Pin VIH VIL tPBW tPBD IPBR PBR Input Threshold High PBR Input Threshold Low PBR Input Pulse Width Manual Reset Propagation Delay PBR Pull-Up Current VCC = 3.3V to 5.5V VCC = 3.3V to 5.5V VCC = 3.3V VCC = 3.3V, VPBR Falling VPBR = 0V
q q q q q q q q q
MIN
TYP 150 0.15 0.05 0.05
MAX
UNITS s
0.4 0.3 0.3
V V V V V
ISOURCE = 1A ISOURCE = 200A
V2 - 1 0.8 * V2
1.6 0.4 150 0.1 -10 1
V V ns s A
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: All voltage values are with respect to GND. Note 3: The greater of V1, V2 is the internal supply voltage (VCC). Note 4: Under static no-fault conditions, V1 will necessarily supply quiescent current. If at any time V2 is larger than V1, V2 must be capable of supplying the quiescent current, programming (transient) current and reference load current.
Note 5: The RST output pin on the LTC2900-1 has an internal pull-up to V2 of typically 6A. However, an external pull-up resistor may be used when faster rise times are required or for VOH voltages greater than V2. Note 6: The push-pull RST output pin on the LTC2900-2 is actively pulled up to V2.
TEST CIRCUITS
V1 V2 V3 V4 LTC2900-1 RST ISOURCE 1A LTC2900-1 V1 V2 V3 V4
2900 F02
RST
ISINK 2.5mA, 100A
V1 V2 V3 V4
LTC2900-2 RST ISOURCE 200A
2900 F01
2900 F03
Figure 1. RST VOH Test
Figure 2. RST VOL Test
Figure 3. Active Pull-Up RST VOH Test
TI I G DIAGRA
VX
VRTX tUV tRST 1.5V tPBD tRST
RST
PBR tPBW
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Monitor Timing
2900 TD
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LTC2900 TYPICAL PERFOR A CE CHARACTERISTICS
5V Threshold Voltage vs Temperature
4.750 THRESHOLD VOLTAGE, VRT33 (V) 3.135 3.125
THESHOLD VOLTAGE, VRT50 (V)
4.725 4.700 4.675 4.650 4.625 4.600 20 40 60 -60 -40 -20 0 TEMPERATURE (C)
3.115 3.105 3.095 3.085 3.075 3.065 3.055 3.045
THRESHOLD VOLTAGE, VRT30 (V)
2.5V Threshold Voltage vs Temperature
2.3750 2.3675
1.710 1.705
THRESHOLD VOLTAGE, VRT25 (V)
THRESHOLD VOLTAGE, VRT18 (V)
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
1.700 1.695 1.690 1.685 1.680 1.675 1.670 1.665 1.660 1.655 -60 -40 -20 0 20 40 60 TEMPERATURE (C) 80 100
THRESHOLD VOLTAGE, VRT15 (V)
ADJ Threshold Voltage vs Temperature
0.508 THRESHOLD VOLTAGE, VRTAN (V)
THRESHOLD VOLTAGE, VRTA (V)
0.506 0.504 0.502 0.500 0.498 0.496 0.494 0.492 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80
0 -0.006 -0.012 -0.018 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C)
VREF (V)
4
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3.3V Threshold Voltage vs Temperature
2.850 2.840 2.830 2.820 2.810 2.800 2.790 2.780 2.770 80 100
3V Threshold Voltage vs Temperature
80 100
2900 G01
3.035 -60 -40 - 20 0 20 40 60 TEMPERATURE (C)
2.760 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C)
80
100
2900 G02
2900 G03
1.8V Threshold Voltage vs Temperature
1.425 1.420 1.415 1.410 1.405 1.400 1.395 1.390 1.385
1.5V Threshold Voltage vs Temperature
1.380 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C)
80
100
2900 G04
2900 G05
2900 G06
- ADJ Threshold Voltage vs Temperature
0.018 0.012 0.006 1.228 1.222 1.216 1.210 1.204 1.198
VREF vs Temperature
100
80
100
1.192 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C)
80
100
2900 G07
2900 G08
2900 G21
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LTC2900 TYPICAL PERFOR A CE CHARACTERISTICS
IV1 vs Temperature
100 V1 = 5V 90 V2 = 3.3V V3 = 2.5V 80 V4 = 1.8V 70
IV2 (A)
IV1 (A)
50 40 30 20 10 0 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100
1.0 0.9 0.8 0.7 0.6 0.5 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100
IV3 (A)
60
IV4 vs Temperature
1.0
TYPICAL TRANSIENT DURATION (s)
TYPICAL TRANSIENT DURATION (s)
V1 = 5V 0.9 V2 = 3.3V V3 = 2.5V 0.8 V4 = 1.8V 0.7
IV4 (A)
0.6 0.5 0.4 0.3 0.2 0.1 0 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100
RST Output Voltage vs V1, VPG = 0V
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RST OUTPUT VOLTAGE (V)
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RESET TIME-OUT PERIOD, tRST (sec)
RESET TIME-OUT PERIOD, tRST (ms)
V1 = V2 = V3 = V4 10k PULL-UP FROM RST TO V1 TA = 25C
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2
1
0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 V1 (V)
2900 G14
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2900 G09 2900 G12
IV2 vs Temperature
1.5 V1 = 5V 1.4 V2 = 3.3V V3 = 2.5V 1.3 V4 = 1.8V 1.2 1.1 1.1
IV3 vs Temperature
V1 = 5V 1.0 V2 = 3.3V V3 = 2.5V 0.9 V4 = 1.8V 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 - 60 -40 - 20 0 20 40 60 TEMPERATURE (C) 80 100
2900 G10
2900 G11
Typical Transient Duration vs Comparator Overdrive (V1, V2)
450 400 350 300 250 200 150 100 50 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX)
2900 G13
Typical Transient Duration vs Comparator Overdrive (V3, V4)
220 200 180 160 140 120 100 80 60 40 20 0 1 10 100 0.1 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX)
2900 G20
TA = 25C
TA = 25C RESET OCCURS ABOVE CURVE
RESET OCCURS ABOVE CURVE
Reset Time-Out Period vs Temperature
CRT = 1500pF 8.4 (SILVER MICA) 7.9 7.4 6.9 6.4 5.9 5.4 4.9 -60 -40 -20 0 20 40 60 TEMPERATURE (C) 80 100 8.9
10
Reset Time-Out Period vs Capacitance
TA = 25C
1
100m
10m
1m
100 10p
100p
10n 1n CRT (FARAD)
100n
1
2900 G16
2900 G15
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LTC2900 TYPICAL PERFOR A CE CHARACTERISTICS
RST, ISINK vs Supply Voltage
13 T = 25C 12 A 11 10 9 8 7 6 5 4 3 2 1 0 1 0 3.0 V2 = 3V V1 = 5V 2.5 85C VOL = 0.4V 2.0 - 40C 2.5 VOH (V) 2.0 - 40C 1.5 1.0 85C 0.5 0 0.5 0 0 10 20 30 50 60 ISINK (mA) 40 70 80 90 0 0.5 1 1.5 ISOURCE (mA) 2 2.5
2900 G19
ISINK (mA)
VOL (V)
VOL = 0.2V
2
3 4 V1 OR V2 (V)
RST Pull-Up Current vs V2 (LTC2900-1)
20 18 16 PULL-UP CURRENT (A) 14 12 10 8 6 4 2 0 2 2.5 3 3.5 V2 (V) 4 4.5 5
2900 G22
TA = 25C
PULL-UP CURRENT (mA)
VRT30 VRT25
PI FU CTIO S
V3 (Pin 1): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V or ADJ. See Table 1 for details. V1 (Pin 2): Voltage Input 1. Select from 5V or 3.3V. See Table 1 for details. The greater of (V1, V2) is also VCC for the chip. Bypass this pin to ground with a 0.1F (or greater) capacitor. CRT (Pin 3): Reset Delay Time Programming Pin. Attach an external capacitor (CRT) to GND to set a reset delay time of 4.6ms/nF. Leaving the pin open generates a minimum delay of approximately 50s. A 47nF capacitor will generate a 216ms reset delay time. RST (Pin 4): Reset Logic Output. Active low with weak pull-up to V2 (LTC2900-1) or active pull-up to V2 (LTC2900-2). Pulls low when any voltage input is below the reset threshold and held low for programmed delay time after all voltage inputs are above threshold. May be pulled above V2 using an external pull-up (LTC2900-1 only).
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2900 G17
RST Voltage Output Low vs Output Sink Current
3.5 25C 3.0
RST High Level Output Voltage vs Output Source Current (LTC2900-2)
V1 = 5V V2 = 3V V3 = 2.5V V4 = 1V
1.5 1.0
25C
6
2900 G18
RST Pull-Up Current vs V2 (LTC2900-2)
6 5 4 3 2 1 0 2 2.5 3 3.5 V2 (V) 4 4.5 5
2900 G23
TA = 25C
VRT33
VRT33 VRT30 VRT25
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LTC2900
PI FU CTIO S
PBR (Pin 5): Manual Reset Pin. Attach push-button switch between this pin and ground. A logic low on this pin will pull RST low. When the PBR pin returns high, RST will return high after the programmed reset delay assuming all four voltage inputs are above threshold. A weak internal pull-up allows the pin to be left floating for normal monitor operation. When using a switch, the switch is debounced through the reset circuitry using the delay provided by the CRT timing capacitor. GND (Pin 6): Ground. VPG (Pin 7): Voltage Threshold Combination Select Input. Connect to an external 1% resistive divider between VREF and GND to select 1 of 16 combinations of preset and/or adjustable voltage thresholds (see Table 1). Do not add capacitance on the VPG pin. VREF (Pin 8): Buffered Reference Voltage. A 1.210V nominal reference used for the programming voltage (VPG) and for the offset of negative adjustable applications. The buffered reference can source and sink up to 1mA. The reference can drive a bypass capacitor of up to 1000pF without oscillation. V4 (Pin 9): Voltage Input 4. Select from 1.8V, 1.5V, ADJ or - ADJ. See Table 1 for details. V2 (Pin 10): Voltage Input 2. Select from 3.3V, 3V or 2.5V. See Table 1 for details. The greater of (V1, V2) is also VCC for the chip. Bypass this pin to ground with a 0.1F (or greater) capacitor. RST is weakly pulled up to V2 (LTC2900-1). RST is actively pulled up to V2 in the LTC2900-2.
BLOCK DIAGRA
V3 1 V4 9 GND 6
RESISTIVE DIVIDER MATRIX
VPG 7 A/D BUFFER VREF 8 1.210V
+
V2 10
+
+
-
V1 2
+
-
-
-
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V1
POWER DETECT
VCC
V2
LTC2900-1 V2 6A RST 4 ADJUSTABLE RESET PULSE GENERATOR
VCC 2A LTC2900-2 V2
22A BANDGAP REFERENCE
10A VCC PBR 5 3 CRT CRT
2900 DB-1
RST 4
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LTC2900
APPLICATIO S I FOR ATIO
Power-Up The greater of V1, V2 is the internal supply voltage (VCC). On power-up, VCC will power the drive circuits for the RST pin. This ensures that the RST output will be low as soon as V1 or V2 reaches 1V. The RST output will remain low until the part is programmed. After programming, if any one of the VX inputs is below its programmed threshold, RST will be a logic low. Once all the VX inputs rise above their thresholds, an internal timer is started and RST is released after the programmed delay time. If VCC < (V3 - 1) and VCC < 2.4V, the V3 input impedance will be low (1k typ). Monitor Programming The LTC2900 input voltage combination is selected by placing the recommended resistive divider from VREF to GND and connecting the tap point to VPG, as shown in Figure 4. Table 1 offers recommended 1% resistor values
LTC2900 8 VREF 7 VPG 6 GND R1 1% R2 1%
2900 F04
Figure 4. Monitor Programming Table 1. Voltage Threshold Programming
MODE 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 V1 (V) V2 (V) V3 (V) V4 (V) R1 (k) R2 (k) 5.0 5.0 3.3 3.3 3.3 5.0 5.0 5.0 5.0 5.0 3.3 3.3 3.3 5.0 5.0 5.0 3.3 3.3 2.5 2.5 2.5 3.3 3.3 3.3 3.0 3.0 2.5 2.5 2.5 3.3 3.3 3.0 ADJ ADJ ADJ ADJ 1.5 2.5 2.5 2.5 2.5 ADJ 1.8 1.8 1.8 1.8 1.8 1.8 ADJ -ADJ ADJ -ADJ ADJ ADJ 1.8 1.5 ADJ ADJ 1.5 ADJ -ADJ -ADJ ADJ ADJ Open 93.1 86.6 78.7 71.5 66.5 59.0 53.6 47.5 40.2 34.8 28.0 22.1 16.2 9.53 Short Short 9.53 16.2 22.1 28.0 34.8 40.2 47.5 53.6 59.0 66.5 71.5 78.7 86.6 93.1 Open VPG VREF 0.000 0.094 0.156 0.219 0.281 0.344 0.406 0.469 0.531 0.594 0.656 0.719 0.781 0.844 0.906 1.000
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for the various modes. The last column in Table 1 specifies optimum VPG/VREF ratios (0.01) to be used when programming with a ratiometric DAC. During power-up, once V1 or V2 reaches 2.4V max, the monitor enters a programming period of approximately 150s during which the voltage on the VPG pin is sampled and the monitor is configured to the desired input combination. Do not add capacitance to the VPG pin. Immediately after programming, the comparators are enabled and supply monitoring will begin. Supply Monitoring The LTC2900 is a low power, high accuracy programmable quad supply monitoring circuit with a common reset output and a manual reset input. Reset timing is adjustable using an external capacitor. Single pin programming selects 1 of 16 input voltage monitor combinations. All four voltage inputs must be above predetermined thresholds for the reset not to be invoked. The LTC2900 will assert the reset output during power-up, power-down and brownout conditions on any one of the voltage inputs. The inverting inputs on the V3 and/or V4 comparators are set to 0.5V when the positive adjustable modes are selected (Figure 5). The tap point on an external resistive divider, connected between the positive voltage being sensed and ground, is connected to the high impedance noninverting inputs (V3, V4). The trip voltage is calculated from: R3 VTRIP = 0.5V 1 + R4 In the negative adjustable mode, the noninverting input on the V4 comparator is connected to ground (Figure 6). The tap point on an external resistive divider, connected between the negative voltage being sensed and the VREF pin, is connected to the high impedance inverting input (V4). VREF provides the necessary level shift required to operate at ground. The trip voltage is calculated from: R3 VTRIP = - VREF ; VREF = 1.210 V No min al R4 In a negative adjustable application, the minimum value for R4 is limited by the sourcing capability of VREF (1mA).
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LTC2900
APPLICATIO S I FOR ATIO
VTRIP R3 1% V3 OR V4 R4 1% LTC2900
+ - + -
0.5V
2900 F05
Figure 5. Setting the Positive Adjustable Trip Point
8 R4 1% R3 1% VTRIP VREF LTC2900
9 V4
- +
2900 F06
Figure 6. Setting the Negative Adjustable Trip Point
With no other load on VREF, R4 (minimum) is: 1.21V / 1mA = 1.21k. Tables 2 and 3 offer suggested 1% resistor values for various adjustable applications. Although all four supply monitor comparators have builtin glitch immunity, bypass capacitors on V1 and V2 are recommended because the greater of V1 or V2 is also the VCC for the chip. Filter capacitors on the V3 and V4 inputs are allowed. Power-Down On power-down, once any of the VX inputs drop below their threshold, RST is held at a logic low. A logic low of 0.4V is guaranteed until both V1 and V2 drop below 1V. If the bandgap reference becomes invalid (VCC < 2V typ), the part will reprogram once VCC rises above 2.4V max. Monitor Output Rise and Fall Time Estimation The RST output has strong pull-down capability. If the external load capacitance (CLOAD) is known, output fall time (10% to 90%) is estimated using: tFALL 2.2 * RPD * CLOAD
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Table 2. Suggested 1% Resistor Values for the ADJ Inputs
VSUPPLY (V) 12 10 8 7.5 6 5 3.3 3 2.5 1.8 1.5 1.2 1 0.9 VTRIP (V) 11.25 9.4 7.5 7 5.6 4.725 3.055 2.82 2.325 1.685 1.410 1.120 0.933 0.840 R3 (k) 2150 1780 1400 1300 1020 845 511 464 365 237 182 124 86.6 68.1 R4 (k) 100 100 100 100 100 100 100 100 100 100 100 100 100 100
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Table 3. Suggested 1% Resistor Values for the -ADJ Input
VSUPPLY (V) -2 -5 -5.2 -10 -12 VTRIP (V) -1.87 -4.64 -4.87 -9.31 -11.30 R3 (k) 187 464 487 931 1130 R4 (k) 121 121 121 121 121
where RPD is the on-resistance of the internal pull-down transistor. The typical performance curve (VOL vs ISINK) demonstrates that the pull-down current is somewhat linear versus output voltage. Using the 25C curve, RPD is estimated to be approximately 40. Assuming a 150pF load capacitance, the fall time is about 13.2ns. Although the RST output of the LTC2900-1 is considered to be "open-drain," it does have weak pull-up capability (see RST Pull-Up Current vs V2 curve). Output rise time (10% to 90%) is estimated using: tRISE 2.2 * RPU * CLOAD where RPU is the on-resistance of the pull-up transistor. The on-resistance as a function of the V2 voltage at room temperature is estimated using:
RPU =
6 * 105 V2 - 1
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LTC2900
APPLICATIO S I FOR ATIO
with V2 = 3.3V, RPU is about 260k. Using 150pF for load capacitance, the rise time is 86s. If the output needs to pull up faster and/or to a higher voltage, a smaller external pull-up resistor may be used. Using a 10k pullup resistor, the rise time is reduced to 3.3s for a 150pF load capacitance. The LTC2900-2 has an active pull-up to V2 on the RST output. The typical performance curve (RST Pull-Up Current vs V2 curve) demonstrates that the pull-up current is somewhat linear versus the V2 voltage and RPU is estimated to be approximately 625. A 150pF load capacitance makes the rise time about 206ns. Selecting the Reset Timing Capacitor The reset time-out period is adjustable in order to accommodate a variety of microprocessor applications. The
TYPICAL APPLICATIO S
Quad Supply Monitor with Push-Button Reset 5V, 3V, 1.8V, 12V (ADJ)
1.8V 5V SYSTEM RESET CRT NORMALLY OPEN 1 2 3 V3 V1 V2 V4 10 9 R3 2.15M 1% 12V VTRIP = 11.25V R4 100k 1% 3V
5V, - 5V Monitor and Unused V2, V3 Inputs Pulled Above Trip Thresholds
R3 464k 1% -5V VTRIP = -4.64V R1 R4 16.2k 121k 1% 1% R2 86.6k 1%
2900 TA03
5V SYSTEM RESET CRT
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reset time-out period, tRST, is adjusted by connecting a capacitor, CRT, between the CRT pin and ground. The value of this capacitor is determined by: CRT = tRST * 217.4 * 10 -9 with CRT in Farads and tRST in seconds. The CRT value per millisecond of delay can also be expressed as CRT/ms = 217.4 (pF/ms). Leaving the CRT pin unconnected will generate a minimum reset time-out of approximately 50s. Maximum reset time-out is limited by the largest available low leakage capacitor. The accuracy of the time-out period will be affected by capacitor leakage (the nominal charging current is 2A) and capacitor tolerance. A low leakage ceramic capacitor is recommended.
LTC2900 8 VREF CRT 4 7 RST VPG 6 5 PBR GND
2900 TA02
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1 2 3
V3 V1
V2
10
9 V4 LTC2900 8 VREF CRT 4 7 VPG RST 5 6 GND PBR
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LTC2900
TYPICAL APPLICATIO S
5V, 3.3V, 12V, -5.2V Monitor with Manual Reset and LED Indication on RST
12V R5 VTRIP = 11.25V 2.15M 1% R6 100k 1% 5V RL1 1k LED CRT R3 487k 1% R4 121k 1% R1 93.1k 1% R2 9.53k 1%
2900 TA05
SYSTEM RESET
PACKAGE DESCRIPTIO
5.23 (.206) MIN
0.50 0.305 0.038 (.0197) (.0120 .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT
0.254 (.010) GAUGE PLANE
0.18 (.007) SEATING PLANE 0.17 - 0.27 (.007 - .011) 0.13 0.05 (.005 .002)
MSOP (MS) 0402
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
2900i
U
U
1 2 3
V3
V2
10
3.3V
10k*
9 V4 V1 LTC2900-1 8 VREF CRT 4 7 VPG RST 5 6 GND PBR
-5.2V VTRIP = -4.87V
MANUAL RESET BUTTON (NORMALLY OPEN) *OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE
MS Package 10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
0.889 0.127 (.035 .005)
3.2 - 3.45 (.126 - .136) 3.00 0.102 (.118 .004) (NOTE 3) 10 9 8 7 6
0.497 0.076 (.0196 .003) REF
DETAIL "A" 0 - 6 TYP
4.88 0.10 (.192 .004)
3.00 0.102 (.118 .004) NOTE 4
12345 0.53 0.01 (.021 .006) DETAIL "A" 1.10 (.043) MAX 0.86 (.034) REF
0.50 (.0197) TYP
11
LTC2900
TYPICAL APPLICATIO
R5 86.6k 1% 1V VTRIP = 0.933V 3.3V SYSTEM RESET CRT
R6 100k 1%
RELATED PARTS
PART NUMBER LTC690 LTC694-3.3 LTC699 LTC1232 LTC1326 LTC1326-2.5 LTC1536 LTC1726-2.5 LTC1726-5 LTC1727-2.5/LTC1727-5 LTC1728-1.8/LTC1728-3.3 LTC1728-2.5/LTC1728-5 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 AJD Precision Triple Supply Monitor for PCI Applications Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ Micropower Triple Supply Monitor for 5V, 3.3V and ADJ Micropower Triple Supply Monitors with Open-Drain Reset Micropower Triple Supply Monitors with Open-Drain Reset Micropower Triple Supply Monitors with Open-Drain Reset Micropower Triple Supply Monitor with Push-Pull Reset Output 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%) Meets PCI tFAIL Timing Specifications Adjustable RESET and Watchdog Time-Outs Adjustable RESET and Watchdog Time-Outs Individual Monitor Outputs in MSOP 5-Lead SOT-23 Package 5-Lead SOT-23 Package 5-Lead SOT-23 Package
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
Low Voltage Quad Supply Monitor 3.3V, 2.5V, 1V (ADJ), 0.9V (ADJ)
1 2 3 V3 V1 V2 10 2.5V 9 V4 LTC2900 8 VREF CRT 4 7 RST VPG 6 5 PBR GND R3 68.1k 1% 0.9V VTRIP = 0.84V R1 86.6k 1% R2 16.2k 1% R4 100k 1%
2900 TA04
2900i LT/TP 0602 1.5K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2002

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