LTC2902-2IGN

LTC2902 Programmable Quad Supply Monitor with Adjustable Reset Timer and Supply Tolerance DESCRIPTIO The LTC®2902 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 digitally programmable to 5%, 7.5%, 10% or 12.5% below the nominal operating voltage, and are accurate to 1.5% over temperature. All four voltage comparator outputs are connected to separate pins for individual supply monitoring. The reset delay time is adjustable using an external capacitor. 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 and may be disabled during supply margin testing. The LTC2902-1 features an open-drain RST output, while the LTC2902-2 has a push-pull RST output. The 43µA supply current makes the LTC2902 ideal for power conscious systems and the part may be configured to monitor less than four inputs. The LTC2902-1/LTC2902-2 are available in the 16-lead narrow SSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. FEATURES s s s s s s s s s s s s 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 Selectable Supply Tolerance: 5%, 7.5%, 10%, 12.5% Below Monitored Voltage Low Supply Current: 43µA Typ Adjustable Reset Time RESET Disable Pin for Margining Applications Open-Drain RST Output (LTC2902-1) Push-Pull RST Output (LTC2902-2) Individual Nondelayed Monitor Outputs for Each Supply Power Supply Glitch Immunity Guaranteed RESET for VCC ≥ 1V APPLICATIO S s s s s s Desktop and Notebook Computers Multivoltage Systems Telecom Equipment Portable Battery-Powered Equipment Network Servers TYPICAL APPLICATIO Quad Supply Monitor with Adjustable Tolerance (5V, 3.3V, 2.5V, 1.8V) 5V 3.3V DC/DC CONVERTER 2.5V 1.8V 13 R3 POWER 10k V4 GOOD 2 V1 COMP1 16 COMP2 14 1 V2 COMP3 15 LTC2902-2 COMP4 6 12 VREF RST 8 RDIS MARGIN 7 T0 TOLERANCE = 5% 11 9 VPG T1 GND CRT tRST = 216ms 10 5 CRT 47nF 2902 TA01 4 V3 3 SYSTEM LOGIC C1 0.1µF C2 0.1µF R1 59k 1% R2 40.2k 1% U U U 2902f 1 LTC2902 ABSOLUTE (Notes 1, 2, 3) AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW COMP3 COMP1 V3 V1 CRT RST T0 RDIS 1 2 3 4 5 6 7 8 16 COMP2 15 COMP4 14 V2 13 V4 12 VREF 11 VPG 10 GND 9 T1 V1, V2, V3, V4, VPG ..................................... – 0.3V to 7V RST (LTC2902-1)........................................ – 0.3V to 7V RST (LTC2902-2).......................... – 0.3V to (V2 + 0.3V) COMPX, RDIS ............................................. – 0.3V to 7V T0, T1 .......................................... – 0.3V to (VCC + 0.3V) CRT ............................................. – 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 LTC2902-1C/LTC2902-2C ....................... 0°C to 70°C LTC2902-1I/LTC2902-2I .................... –40°C to 85°C Storage Temperature Range .................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................... 300°C ORDER PART NUMBER LTC2902-1CGN LTC2902-2CGN LTC2902-1IGN LTC2902-2IGN GN16 PART MARKING 29021 29022 29021I 29022I GN PACKAGE 16-LEAD PLASTIC SSOP TJMAX = 125°C, θJA = 130°C/W Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS SYMBOL VRT50 PARAMETER 5V, 5% Reset Threshold 5V, 7.5% Reset Threshold 5V, 10% Reset Threshold 5V, 12.5% Reset Threshold 3.3V, 5% Reset Threshold 3.3V, 7.5% Reset Threshold 3.3V, 10% Reset Threshold 3.3V, 12.5% Reset Threshold 3V, 5% Reset Threshold 3V, 7.5% Reset Threshold 3V, 10% Reset Threshold 3V, 12.5% Reset Threshold 2.5V, 5% Reset Threshold 2.5V, 7.5% Reset Threshold 2.5V, 10% Reset Threshold 2.5V, 12.5% Reset Threshold 1.8V, 5% Reset Threshold 1.8V, 7.5% Reset Threshold 1.8V, 10% Reset Threshold 1.8V, 12.5% Reset Threshold 1.5V, 5% Reset Threshold 1.5V, 7.5% Reset Threshold 1.5V, 10% Reset Threshold 1.5V, 12.5% Reset Threshold ADJ, 5% Reset Threshold ADJ, 7.5% Reset Threshold ADJ, 10% Reset Threshold ADJ, 12.5% Reset Threshold The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted. (Note 3) CONDITIONS V1 Input Threshold q q q q q 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 4.475 4.350 4.225 3.036 2.954 2.871 2.789 2.760 2.685 2.610 2.535 2.300 2.238 2.175 2.113 1.656 1.611 1.566 1.521 1.380 1.343 1.305 1.268 0.492 0.479 0.466 0.453 TYP 4.675 4.550 4.425 4.300 3.086 3.003 2.921 2.838 2.805 2.730 2.655 2.580 2.338 2.275 2.213 2.150 1.683 1.638 1.593 1.548 1.403 1.365 1.328 1.290 0.500 0.487 0.473 0.460 MAX 4.750 4.625 4.500 4.375 3.135 3.053 2.970 2.888 2.850 2.775 2.700 2.625 2.375 2.313 2.250 2.188 1.710 1.665 1.620 1.575 1.425 1.388 1.350 1.313 0.508 0.494 0.481 0.467 UNITS V V V V V V V V V V V V V V V V V V V V V V V V V V V V 2902f VRT33 V1, V2 Input Threshold VRT30 V2 Input Threshold VRT25 V2, V3 Input Threshold VRT18 V3, V4 Input Threshold VRT15 V3, V4 Input Threshold VRTA V3, V4 Input Threshold 2 U W U U WW W LTC2902 ELECTRICAL CHARACTERISTICS SYMBOL VRTAN VCC VCCMINP VCCMINC VREF PARAMETER – ADJ Reset Threshold Minimum Internal Operating Voltage Minimum Required for Programming Minimum Required for Comparators Reference Voltage The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted. (Note 3) CONDITIONS V4 Input Threshold RST, COMPX in Correct Logic State; VCC Rising Prior to Program VCC Rising VCC Falling VCC ≥ 2.3V, IVREF = ± 1mA, CREF ≤ 1000pF T0 Low, T1 Low T0 Low, T1 High T0 High, T1 Low T0 High, T1 High VCC ≥ VCCMINP VPG = VREF V1 = 5V, IVREF = 12µA, (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 VX Less Than Reset Threshold VRTX by More Than 1% ISINK = 2.5mA; V1 = 3V, V2 = 3V; V3, V4 = 0V; VPG = 0V ISINK = 100µA; V2 = 1V; V1, V3, V4 = 0V ISINK = 100µA; V1 = 1V; V2, V3, V4 = 0V VOH VOH Output Voltage High RST, COMPX (Note 5) Output Voltage High RST (LTC2902-2) (Note 6) T0, T1 Low Level Input Voltage T0, T1 High Level Input Voltage T0, T1 Input Current RDIS Input Threshold Low RDIS Input Threshold High RDIS Pull-Up Current ISOURCE = 1µA ISOURCE = 200µA q q q q q q q q q q q q q q q q q q MIN – 18 TYP 0 MAX 18 1 2.42 2.32 UNITS mV V V V V V V V V nA µA µA µA nA µA nA nA µA µA ms µs 1.192 1.160 1.128 1.096 0 1.210 1.178 1.146 1.113 1.228 1.195 1.163 1.130 VREF ± 20 VPG IVPG IV1 IV2 IV3 IV4 Programming Voltage Range VPG Input Current V1 Input Current V2 Input Current V3 Input Current V4 Input Current 43 0.8 0.52 –15 0.34 –15 –15 –1.4 10 5 –2 20 7 150 0.15 0.05 0.05 V2 – 1 0.8 • V2 75 2 1.2 15 0.8 15 15 –2.6 30 9 q q q q q q ICRT(UP) ICRT(DN) tRST tUV VOL CRT Pull-Up Current CRT Pull-Down Current Reset Time-Out Period VX Undervoltage Detect to RST or COMPX Output Voltage Low RST, COMPX 0.4 0.3 0.3 V V V V V Digital Inputs T0, T1, RDIS VIL VIH IINTOL VIL VIH IRDIS VCC = 3.3V to 5.5V VCC = 3.3V to 5.5V T0 = 0V, T1 = VCC VCC = 3.3V to 5.5V VCC = 3.3V to 5.5V VRDIS = 0V q q q q q 0.3VCC 0.7VCC ± 0.1 0.4 1.6 –10 ±1 V V µA V V µA 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 output pins RST and COMPX have internal pull-ups to V2 of typically 6µA. However, external pull-up resistors 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 LTC2902-2 is actively pulled up to V2. 2902f 3 LTC2902 TEST CIRCUITS V1 V2 V3 V4 RST LTC2902-1 OR COMPX ISOURCE 1µA 2902 F01 LTC2902-1 V1 V2 V3 V4 2902 F02 RST OR COMPX ISINK 2.5mA, 100µA V1 V2 V3 V4 LTC2902-2 RST ISOURCE 200µA 2902 F03 Figure 1. RST, COMPX VOH Test Figure 2. RST, COMPX VOL Test Figure 3. Active Pull-Up RST VOH Test TI I G DIAGRA TYPICAL PERFOR A CE CHARACTERISTICS 5V Threshold Voltage vs Temperature 4.75 4.70 3.135 5% 3.100 THRESHOLD VOLTAGE, VRT33 (V) THRESHOLD VOLTAGE, VRT50 (V) 4.65 4.60 4.55 4.50 4.45 4.40 4.35 4.30 4.25 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 12.5% 10% 7.5% 3.065 3.030 2.995 2.960 2.925 2.890 2.855 2.820 2.785 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 12.5% 10% 7.5% THRESHOLD VOLTAGE, VRT30 (V) 4 UW W VX Monitor Timing VRTX tUV RST tRST 1.5V VX 2902 TD UW COMPX 3.3V Threshold Voltage vs Temperature 2.850 5% 2.815 2.780 2.745 2.710 2.675 2.640 2.605 2.570 3V Threshold Voltage vs Temperature 5% 7.5% 10% 12.5% 2.535 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 2902 G01 2902 G02 2902 G03 2902f LTC2902 TYPICAL PERFOR A CE CHARACTERISTICS 2.5V Threshold Voltage vs Temperature 2.375 2.350 5% THRESHOLD VOLTAGE, VRT18 (V) 1.710 1.685 1.660 7.5% 1.635 1.610 1.585 1.560 1.535 1.510 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 12.5% 10% THRESHOLD VOLTAGE, VRT25 (V) 2.325 2.300 2.275 2.250 2.225 2.200 2.175 2.150 2.125 2.100 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 12.5% 10% 7.5% THRESHOLD VOLTAGE, VRT15 (V) ADJ Threshold Voltage vs Temperature 0.508 0.503 5% THRESHOLD VOLTAGE, VRTAN (V) 0.012 0.006 0.018 THRESHOLD VOLTAGE, VRTA (V) 0.498 0.493 0.488 0.483 0.478 0.473 0.468 0.463 0.458 0.453 – 60 – 40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 12.5% 10% 7.5% VREF (V) IV1 vs Temperature 100 V1 = 5V 90 V2 = 3.3V V3 = 2.5V 80 V4 = 1.8V 70 IV2 (µA) IV1 (µA) 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 (µA) 60 UW 1.8V Threshold Voltage vs Temperature 1.425 5% 1.405 1.385 1.365 1.345 1.5V Threshold Voltage vs Temperature 5% 7.5% 10% 1.325 1.305 1.285 1.265 – 60 – 40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 12.5% 2902 G04 2902 G05 2902 G06 – ADJ Threshold Voltage vs Temperature 1.228 1.216 1.204 1.192 1.180 1.168 1.156 1.144 1.132 –0.012 –0.018 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 1.112 1.108 80 100 VREF vs Temperature 5% 7.5% 0 –0.006 10% 12.5% 1.096 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 2902 G07 2902 G08 2902 G09 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 2902 G10 2902 G11 2902 G12 2902f 5 LTC2902 TYPICAL PERFOR A CE CHARACTERISTICS IV4 vs Temperature TYPICAL TRANSIENT DURATION (µs) 1.0 V1 = 5V 0.9 V2 = 3.3V V3 = 2.5V 0.8 V4 = 1.8V 0.7 TYPICAL TRANSIENT DURATION (µs) IV4 (µA) 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 5 RESET TIME-OUT PERIOD, tRST (ms) RESET TIME-OUT PERIOD, tRST (sec) RST OUTPUT VOLTAGE (V) 4 V1 = V2 = V3 = V4 10k PULL-UP FROM RST TO V1 TA = 25°C 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 V1 (V) 2902 G15 RST, COMPX ISINK vs Supply Voltage 10 9 8 7 ISINK (mA) 6 5 4 3 2 1 0 0 1 2 3 4 V1 OR V2 (V) 5 6 2902 G18 TA = 25°C VOL = 0.4V 2.0 VOL (V) 1.5 1.0 0.5 0 VOH (V) VOL = 0.2V 6 UW 2902 G13 Typical Transient Duration vs Comparator Overdrive (V1, V2) 450 400 350 300 250 200 150 100 50 RESET OCCURS ABOVE CURVE TA = 25°C 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) 2902 G25 TA = 25°C RESET OCCURS ABOVE CURVE 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 2902 G14 Reset Time-Out Period vs Temperature 8.9 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 Reset Time-Out Period vs Capacitance 10 TA = 25°C 1 100m 10m 1m 100µ 10p 100p 10n 1n CRT (FARAD) 100n 1µ 2902 G17 2902 G16 RST, COMPX Voltage Output Low vs Output Sink Current 3.0 V2 = 3V V1 = 5V 2.5 85°C 25°C 3.0 – 40°C 2.5 2.0 1.5 1.0 0.5 0 0 10 20 30 50 60 ISINK (mA) 40 70 80 90 3.5 RST High Level Output Voltage vs Output Source Current (LTC2902-2) V1 = 5V V2 = 3V V3 = 2.5V V4 = 1V – 40°C 25°C 85°C 0 0.5 1 1.5 ISOURCE (mA) 2 2.5 2902 G20 2902 G19 2902f LTC2902 TYPICAL PERFOR A CE CHARACTERISTICS COMPX Pull-Up Current vs V2 (COMPX Held at 0V) 20 18 16 PULL-UP CURRENT (µA) TA = 25°C COMPX PROPAGATION DELAY (µs) 14 12 10 8 6 4 2 0 1 1.5 2 2.5 3 3.5 V2 (V) 4 4.5 5 RST Pull-Up Current vs V2 (LTC2902-1) 20 18 PULL-UP CURRENT (mA) TA = 25°C 16 PULL-UP CURRENT (µA) 14 12 10 8 6 4 2 0 2 2.5 3 3.5 V2 (V) 4 4.5 5 2902 G23 VRT33 VRT30 VRT25 PI FU CTIO S COMP3 (Pin 1): Comparator Output 3. Nondelayed, active high logic output with weak pull-up to V2. Pulls high when V3 is above reset threshold. May be pulled greater than V2 using external pull-up. COMP1 (Pin 2): Comparator Output 1. Nondelayed, active high logic output with weak pull-up to V2. Pulls high when V1 is above reset threshold. May be pulled greater than V2 using external pull-up. V3 (Pin 3): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V or ADJ. See Table 1 for details. V1 (Pin 4): 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 0.1µF (or greater) capacitor. CRT (Pin 5): 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 50µs. A 47nF capacitor will generate a 216ms reset delay time. UW COMPX Propagation Delay vs Input Overdrive Above Threshold 250 TA = 25°C 200 150 100 V1, V2 50 V3, V4 0 1000 10 100 INPUT OVERDRIVE ABOVE THRESHOLD (mV) 2902 G22 2902 G21 RST Pull-Up Current vs V2 (LTC2902-2) 6 5 4 3 2 1 0 2 2.5 3 3.5 V2 (V) 4 4.5 5 2902 G24 TA = 25°C VRT33 VRT30 VRT25 U U U 2902f 7 LTC2902 PI FU CTIO S RST (Pin 6): Reset Logic Output. Active low with weak pull-up to V2 (LTC2902-1) or active pull-up to V2 (LTC2902-2). 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 (LTC2902-1 only). T0 (Pin 7): Digital Input for Supply Tolerance Selection (5%, 7.5%, 10% or 12.5%). Used in conjunction with T1 (Pin 9). See Applications Information for tolerance selection chart (Table 4). RDIS (Pin 8): Digital Input for RST Disable. A low input on this pin forces the RST output to V2 (or pull-up voltage). Useful for determining supply margins without issuing reset command to processor. A weak internal pull-up allows pin to be left floating for normal monitor operation. T1 (Pin 9): Digital Input for Supply Tolerance Selection (5%, 7.5%, 10% or 12.5%). Used in conjunction with T0 (Pin 7). See Applications Information for tolerance selection chart (Table 4). GND (Pin 10): Ground. VPG (Pin 11): 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 12): Buffered Reference Voltage. A 1.210V nominal reference used for 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 13): Voltage Input 4. Select from 1.8V, 1.5V, ADJ or – ADJ. See Table 1 for details. V2 (Pin 14): 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 chip. Bypass this pin to ground with a 0.1µF (or greater) capacitor. All logic outputs (COMP1, COMP2, COMP3, COMP4) are weakly pulled up to V2. RST is weakly pulled up to V2 in the LTC2902-1 and RST is actively pulled up to V2 in the LTC2902-2. COMP4 (Pin 15): Comparator Output 4. Nondelayed, active high logic output with weak pull-up to V2. Pulls high when V4 is above reset threshold. May be pulled greater than V2 using external pull-up. COMP2 (Pin 16): Comparator Output 2. Nondelayed, active high logic output with weak pull-up to V2. Pulls high when V2 is above reset threshold. May be pulled greater than V2 using external pull-up. 8 U U U 2902f LTC2902 BLOCK DIAGRA V3 3 V4 13 GND 10 RESISTIVE DIVIDER MATRIX VPG 11 A/D BUFFER VREF 12 BUFFER GAIN ADJUST 7 T0 9 T1 + V2 14 + + – V1 4 + – – – W V1 V2 POWER DETECT VCC 6µA COMP1 V2 2 V2 6µA COMP2 16 V2 6µA COMP3 1 V2 6µA BANDGAP REFERENCE COMP4 15 ADJUSTABLE RESET PULSE GENERATOR VCC 2µA 22µA 10µA VCC V2 LTC2902-1 6µA RST 6 5 CRT CRT LTC2902-2 V2 RST 6 8 RDIS 2902 DB-1 2902f 9 LTC2902 APPLICATIO S I FOR ATIO Power-Up On power-up, the larger of V1 or V2 will power the drive circuits for the RST and the COMPX pins. This ensures that the RST and COMPX outputs will be low as soon as V1 or V2 reaches 1V. The RST and COMPX outputs 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 (1kΩ typ). Monitor Programming The LTC2902 input voltage combination is selected by placing the recommended resistor divider from VREF to GND and connecting the tap point to VPG, as shown in Figure 4. Table 1 offers recommended 1% resistor values 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 150µs 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 LTC2902 is a low power, high accuracy programmable quad supply monitoring circuit with four nondelayed monitor outputs, a common reset output and selectable supply thresholds. Reset timing is adjustable using an external capacitor. Single pin programming selects 1 of 16 input voltage monitor combinations. Two digital inputs select one of four supply tolerances (5%, 7.5%, 10% or 12.5%). All four voltage inputs must be above predetermined thresholds for the reset not to be invoked. The LTC2902 will assert the reset and comparator outputs during power-up, power-down and brownout conditions on any one of the voltage inputs. 10 U LTC2902 12 VREF 11 VPG 10 GND R1 1% R2 1% 2902 F04 W UU 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 (kΩ) R2 (kΩ) 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 The inverting inputs on the V3 and/or V4 comparators are set to 0.5V when the positive adjustable modes are selected and with T0 and T1 low (5% tolerance) (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  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%, 12.5%) because the internal reference is scaled accordingly, moving the trip point in – 2.5% increments. 2902f LTC2902 APPLICATIO S I FOR ATIO VTRIP R3 1% V3 OR V4 R4 1% LTC2902 + – + – 0.5V 5% TOLERANCE MODE 2902 F05 Figure 5. Setting the Positive Adjustable Trip Point 12 R4 1% R3 1% VTRIP VREF LTC2902 13 V4 – + 2902 F06 Figure 6. Setting the Negative Adjustable Trip Point 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  R4  T0,T1 Low (5% Tolerance Mode) 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%, 12.5%) because VREF is scaled accordingly, moving the trip point in – 2.5% increments. In a negative adjustable application, the minimum value for R4 is limited by the sourcing capability of VREF (±1mA). With no other load on VREF, R4 (minimum) is: 1.21V ÷ 1mA = 1.21kΩ Tables 2 and 3 offer suggested 1% resistor values for various adjustable applications. U 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 (kΩ) 2150 1780 1400 1300 1020 845 511 464 365 237 182 124 86.6 68.1 R4 (kΩ) 100 100 100 100 100 100 100 100 100 100 100 100 100 100 W UU 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 (kΩ) 187 464 487 931 1130 R4 (kΩ) 121 121 121 121 121 Although all four supply monitor comparators have built-in 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 and COMPX are 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 All of the outputs (RST, COMPX) have strong pull-down capability. If the external load capacitance (CLOAD) for a 2902f 11 LTC2902 APPLICATIO S I FOR ATIO tFALL ≈ 2.2 • RPD • CLOAD particular output is known, output fall time (10% to 90%) is estimated using: 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 25°C curve, RPD is estimated to be approximately 40Ω. Assuming a 150pF load capacitance, the fall time is about 13.2ns. Although the outputs are considered to be “open-drain,” they do have a weak pull-up capability (see COMPX or 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 Ω V2 – 1 with V2 = 3.3V, RPU is about 260k. Using 150pF for load capacitance, the rise time is 86µs. 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 3.3µs for a 150pF load capacitance. The LTC2902-2 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 625Ω. 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 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 • 10 –9 12 U with CRT in Farads and tRST in seconds. The CRT value per millisecond of delay can also be expressed as CRT/ms = 217 (pF/ms). Leaving the CRT pin unconnected will generate a minimum reset time-out of approximately 50µs. 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 2µA) and capacitor tolerance. A low leakage ceramic capacitor is recommended. Tolerance Programming and the RESET Disable Using the two digital inputs T0 and T1, the user can program the global supply tolerance for the LTC2902 (5%, 7.5%, 10%, 12.5%). The larger tolerances provide more headroom by lowering the trip thresholds. Table 4. Tolerance Programming T0 Low Low High High T1 Low High Low High TOLERANCE (%) 5 7.5 10 12.5 VREF (V) 1.210 1.178 1.146 1.113 W UU Under conventional operation, RST and COMPX will go low when VX is below its threshold. At any time, the RDIS pin can be pulled low, overriding the reset operation and forcing the RST pin high. This feature is useful when determining supply margins under processor control since the reset command will not be invoked. The RDIS pin is connected to a weak internal pull-up to VCC (10µA typ), allowing the pin to be left floating if unused. Ensuring RST Valid for VCC Down to 0V (LTC2902-2) When VCC is below 1V the RST pull-down capability is drastically reduced. The RST pin may float to undetermined voltages when connected to high impedance (such as CMOS logic inputs). The addition of a pull-down resistor from RST to ground will provide a path for stray charge and/or leakage currents. The resistor value should be small enough to provide effective pull-down without excessively loading the pull-up circuitry. Too large a value may not pull down well enough. A 100k resistor from RST to ground is satisfactory for most applications. 2902f LTC2902 TYPICAL APPLICATIO S Quad Supply Monitor, 5% Tolerance 5V, 3V, 1.8V, 12V (ADJ) 1 2 1.8V 5V SYSTEM RESET CRT 3 4 5 6 7 8 16 15 14 13 12 11 10 9 R4 100k 1% 3V R3 2.15M 1% 12V VTRIP = 11.25V U COMP3 COMP1 V3 COMP2 COMP4 V2 V1 LTC2902 V4 CRT RST T0 RDIS VREF VPG GND T1 2902 TA02 5V, –5V Monitor with Unused V2, V3 Inputs Pulled Above Trip Thresholds (5% Tolerance) 1 2 3 5V SYSTEM RESET CRT 4 5 6 7 8 COMP3 COMP1 V3 COMP2 COMP4 V2 16 15 14 13 12 11 10 9 R1 R4 16.2k 121k 1% 1% R2 86.6k 1% 2902 TA03 R3 464k 1% –5V VTRIP = – 4.64V V1 LTC2902 V4 CRT RST T0 RDIS VREF VPG GND T1 2902f 13 LTC2902 TYPICAL APPLICATIO S Quad Supply Monitor with LED Undervoltage Indicators, 12.5% Tolerance, Reset Disabled 5V, 3.3V, 2.5V, 1.5V 5V 14 U RL1 1k LED RL3 1k LED 1 2 COMP3 COMP1 V3 COMP2 COMP4 V2 16 15 14 13 12 11 10 9 RL2 1k LED RL4 1k LED 2.5V 3 4 5 6 7 3.3V 1.5V R1 53.6k 1% R2 47.5k 1% V1 LTC2902 V4 CRT RST T0 RDIS VREF VPG GND T1 CRT 8 2902 TA04 2902f LTC2902 PACKAGE DESCRIPTIO .254 MIN .0165 ± .0015 RECOMMENDED SOLDER PAD LAYOUT 1 .015 ± .004 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE *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° – 8° TYP .053 – .068 (1.351 – 1.727) 23 4 56 7 8 .004 – .0098 (0.102 – 0.249) 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. U GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .045 ± .005 .189 – .196* (4.801 – 4.978) 16 15 14 13 12 11 10 9 .009 (0.229) REF .150 – .165 .229 – .244 (5.817 – 6.198) .150 – .157** (3.810 – 3.988) .0250 TYP .008 – .012 (0.203 – 0.305) .0250 (0.635) BSC GN16 (SSOP) 0502 2902f 15 LTC2902 TYPICAL APPLICATIO 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 LTC1728-2.5/LTC1728-5 LTC1985-1.8 LTC2900 LTC2901 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 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 Monitor with Open-Drain Reset Micropower Triple Supply Monitor with Open-Drain Reset Micropower Triple Supply Monitor with Push-Pull Reset Output Programmable Quad Supply Monitor Programmable Quad Supply Monitor COMMENTS 4.65V Threshold 2.9V Threshold 4.65V Threshold 4.37V/4.62V Threshold 4.725V, 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 Adjustable RESET, 10-Lead MSOP Package Adjustable RESET and Watchdog Timer, 16-Lead SSOP Package Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (± 0.75%) LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitor with Open-Drain Reset 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 q FAX: (408) 434-0507 q U Quad Supply Monitor with Hysteresis 5% Tolerance (Supplies Rising) 12.5% Tolerance (After RST Goes High) 5V 4 3.3V 2.5V 1.8V 14 3 13 8 12 R1 59k 1% R2 40.2k 1% 11 10 LTC2902-1 2 COMP1 16 V2 COMP2 1 V3 COMP3 15 V4 COMP4 6 RDIS RST 7 VREF T0 9 T1 VPG 5 CRT GND V1 10k CRT 2902 TA05 2902f LT/TP 1002 2K • PRINTED IN USA www.linear.com © LINEAR TECHNOLOGY CORPORATION 2002