LTC2902-1CGN#PBF

LTC2902 Programmable Quad Supply Monitor with Adjustable Reset Timer and Supply Tolerance DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 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 U APPLICATIO S ■ ■ ■ ■ 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. Desktop and Notebook Computers Multivoltage Systems Telecom Equipment Portable Battery-Powered Equipment Network Servers , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ 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. TYPICAL APPLICATIO Quad Supply Monitor with Adjustable Tolerance (5V, 3.3V, 2.5V, 1.8V) 5V 3.3V DC/DC CONVERTER SYSTEM LOGIC 2.5V 1.8V 3 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 C1 0.1µF C2 0.1µF R1 59k 1% R2 40.2k 1% V3 2902f 1 LTC2902 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Notes 1, 2, 3) 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 TOP VIEW COMP3 1 16 COMP2 COMP1 2 15 COMP4 V3 3 14 V2 V1 4 13 V4 CRT 5 12 VREF RST 6 11 VPG T0 7 10 GND RDIS 8 9 LTC2902-1CGN LTC2902-2CGN LTC2902-1IGN LTC2902-2IGN GN16 PART MARKING T1 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 The ● 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) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT50 5V, 5% Reset Threshold 5V, 7.5% Reset Threshold 5V, 10% Reset Threshold 5V, 12.5% Reset Threshold V1 Input Threshold ● ● ● ● 4.600 4.475 4.350 4.225 4.675 4.550 4.425 4.300 4.750 4.625 4.500 4.375 V V V V VRT33 3.3V, 5% Reset Threshold 3.3V, 7.5% Reset Threshold 3.3V, 10% Reset Threshold 3.3V, 12.5% Reset Threshold V1, V2 Input Threshold ● ● ● ● 3.036 2.954 2.871 2.789 3.086 3.003 2.921 2.838 3.135 3.053 2.970 2.888 V V V V VRT30 3V, 5% Reset Threshold 3V, 7.5% Reset Threshold 3V, 10% Reset Threshold 3V, 12.5% Reset Threshold V2 Input Threshold ● ● ● ● 2.760 2.685 2.610 2.535 2.805 2.730 2.655 2.580 2.850 2.775 2.700 2.625 V V V V VRT25 2.5V, 5% Reset Threshold 2.5V, 7.5% Reset Threshold 2.5V, 10% Reset Threshold 2.5V, 12.5% Reset Threshold V2, V3 Input Threshold ● ● ● ● 2.300 2.238 2.175 2.113 2.338 2.275 2.213 2.150 2.375 2.313 2.250 2.188 V V V V VRT18 1.8V, 5% Reset Threshold 1.8V, 7.5% Reset Threshold 1.8V, 10% Reset Threshold 1.8V, 12.5% Reset Threshold V3, V4 Input Threshold ● ● ● ● 1.656 1.611 1.566 1.521 1.683 1.638 1.593 1.548 1.710 1.665 1.620 1.575 V V V V VRT15 1.5V, 5% Reset Threshold 1.5V, 7.5% Reset Threshold 1.5V, 10% Reset Threshold 1.5V, 12.5% Reset Threshold V3, V4 Input Threshold ● ● ● ● 1.380 1.343 1.305 1.268 1.403 1.365 1.328 1.290 1.425 1.388 1.350 1.313 V V V V VRTA ADJ, 5% Reset Threshold ADJ, 7.5% Reset Threshold ADJ, 10% Reset Threshold ADJ, 12.5% Reset Threshold V3, V4 Input Threshold ● ● ● ● 0.492 0.479 0.466 0.453 0.500 0.487 0.473 0.460 0.508 0.494 0.481 0.467 V V V V 2902f 2 LTC2902 ELECTRICAL CHARACTERISTICS The ● 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) SYMBOL PARAMETER CONDITIONS MIN TYP MAX VRTAN – ADJ Reset Threshold V4 Input Threshold ● VCC Minimum Internal Operating Voltage RST, COMPX in Correct Logic State; VCC Rising Prior to Program VCCMINP Minimum Required for Programming VCCMINC Minimum Required for Comparators VREF Reference Voltage – 18 0 18 mV ● 1 V VCC Rising ● 2.42 V VCC Falling ● 2.32 V VCC ≥ 2.3V, IVREF = ±1mA, CREF ≤ 1000pF T0 Low, T1 Low T0 Low, T1 High T0 High, T1 Low T0 High, T1 High ● ● ● ● 1.192 1.160 1.128 1.096 1.228 1.195 1.163 1.130 V V V V VCC ≥ VCCMINP ● 0 VREF V 1.210 1.178 1.146 1.113 UNITS VPG Programming Voltage Range IVPG VPG Input Current VPG = VREF ● ±20 nA IV1 V1 Input Current V1 = 5V, IVREF = 12µA, (Note 4) ● 43 75 µA IV2 V2 Input Current V2 = 3.3V ● 0.8 2 µA IV3 V3 Input Current V3 = 2.5V V3 = 0.55V (ADJ Mode) ● 0.52 1.2 15 µA nA V4 = 1.8V V4 = 0.55V (ADJ Mode) V4 = –0.05V (–ADJ Mode) ● ● ● 0.34 –15 –15 0.8 15 15 µA nA nA IV4 V4 Input Current –15 ICRT(UP) CRT Pull-Up Current VCRT = 0V ● –1.4 –2 –2.6 µA ICRT(DN) CRT Pull-Down Current VCRT = 1.3V ● 10 20 30 µA tRST Reset Time-Out Period CRT = 1500pF ● 5 7 9 ms tUV VX Undervoltage Detect to RST or COMPX VX Less Than Reset Threshold VRTX by More Than 1% VOL Output Voltage Low RST, COMPX ISINK = 2.5mA; V1 = 3V, V2 = 3V; V3, V4 = 0V; VPG = 0V ● 0.15 0.4 V ISINK = 100µA; V2 = 1V; V1, V3, V4 = 0V ISINK = 100µA; V1 = 1V; V2, V3, V4 = 0V ● ● 0.05 0.05 0.3 0.3 V V µs 150 VOH Output Voltage High RST, COMPX (Note 5) ISOURCE = 1µA ● V2 – 1 V VOH Output Voltage High RST (LTC2902-2) (Note 6) ISOURCE = 200µA ● 0.8 • V2 V VCC = 3.3V to 5.5V ● Digital Inputs T0, T1, RDIS VIL T0, T1 Low Level Input Voltage VIH T0, T1 High Level Input Voltage VCC = 3.3V to 5.5V ● IINTOL T0, T1 Input Current T0 = 0V, T1 = VCC ● VIL RDIS Input Threshold Low VCC = 3.3V to 5.5V ● VIH RDIS Input Threshold High VCC = 3.3V to 5.5V ● IRDIS RDIS Pull-Up Current VRDIS = 0V 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. 0.3VCC V ±1 µA 1.6 V 0.7VCC V ±0.1 0.4 V –10 µA 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 LTC2902-1 V1 V2 V3 V4 ISOURCE 1µA V1 V2 V3 V4 ISINK 2.5mA, 100µA RST OR COMPX 2902 F02 2902 F01 Figure 1. RST, COMPX VOH Test LTC2902-2 RST ISOURCE 200µA 2902 F03 Figure 2. RST, COMPX VOL Test Figure 3. Active Pull-Up RST VOH Test WU W TI I G DIAGRA VX Monitor Timing VRTX VX tRST tUV 1.5V RST 2902 TD COMPX U W TYPICAL PERFOR A CE CHARACTERISTICS 3.3V Threshold Voltage vs Temperature 5V Threshold Voltage vs Temperature 3.135 THRESHOLD VOLTAGE, VRT33 (V) THRESHOLD VOLTAGE, VRT50 (V) 3.100 5% 4.65 4.60 4.55 7.5% 4.50 4.45 10% 4.40 4.35 12.5% 3.065 3.030 7.5% 2.995 2.960 2.925 10% 2.890 2.855 12.5% 80 100 2902 G01 2.785 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 2.815 5% 2.780 2.745 7.5% 2.710 2.675 10% 2.640 2.605 12.5% 2.570 2.820 4.30 4.25 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 2.850 5% THRESHOLD VOLTAGE, VRT30 (V) 4.75 4.70 3V Threshold Voltage vs Temperature 80 100 2902 G02 2.535 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 2902 G03 2902f 4 LTC2902 U W TYPICAL PERFOR A CE CHARACTERISTICS 2.5V Threshold Voltage vs Temperature 1.8V Threshold Voltage vs Temperature 1.710 THRESHOLD VOLTAGE, VRT25 (V) 2.350 THRESHOLD VOLTAGE, VRT18 (V) 5% 2.325 2.300 7.5% 2.275 2.250 10% 2.225 2.200 2.175 12.5% 2.150 2.125 2.100 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 1.425 5% 1.685 1.660 7.5% 1.635 1.610 10% 1.585 1.560 12.5% 1.535 1.510 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 2902 G04 80 1.305 12.5% 1.285 10% 0.473 0.468 12.5% 80 100 VREF vs Temperature 1.228 0.012 5% 1.204 1.192 0.006 7.5% 1.180 VREF (V) THRESHOLD VOLTAGE, VRTAN (V) 7.5% 0.483 0 1.168 1.156 10% 1.144 –0.006 1.132 1.112 –0.012 0.458 12.5% 1.108 0.453 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 –0.018 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 2902 G07 80 100 1.096 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 2902 G08 IV1 vs Temperature V1 = 5V 1.0 V2 = 3.3V V3 = 2.5V 0.9 V4 = 1.8V 0.8 60 1.1 0.7 IV3 (µA) V1 = 5V 1.4 V2 = 3.3V V3 = 2.5V 1.3 V4 = 1.8V 1.2 IV2 (µA) V1 = 5V 90 V2 = 3.3V V3 = 2.5V 80 V4 = 1.8V 70 1.1 40 1.0 0.9 0.6 0.5 30 0.8 0.4 20 0.7 0.3 10 0.6 0.2 0.5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 0.1 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 0 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 2902 G10 100 IV3 vs Temperature 1.5 50 80 2902 G09 IV2 vs Temperature 100 IV1 (µA) 10% 1.325 1.216 0.493 0.463 1.345 2902 G06 5% 0.498 0.478 7.5% 1.365 1.265 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 0.018 0.488 1.385 – ADJ Threshold Voltage vs Temperature 0.508 0.503 5% 1.405 2902 G05 ADJ Threshold Voltage vs Temperature THRESHOLD VOLTAGE, VRTA (V) THRESHOLD VOLTAGE, VRT15 (V) 2.375 1.5V Threshold Voltage vs Temperature 80 100 2902 G11 80 100 2902 G12 2902f 5 LTC2902 U W TYPICAL PERFOR A CE CHARACTERISTICS 0.6 0.5 0.4 0.3 0.2 0.1 0 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 TA = 25°C 400 350 RESET OCCURS ABOVE CURVE 300 250 200 150 100 50 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 3 2 1 0 120 100 80 60 40 20 0 1 10 100 0.1 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 2902 G25 Reset Time-Out Period vs Capacitance 10 CRT = 1500pF 8.4 (SILVER MICA) 7.9 7.4 6.4 5.9 5.4 4.9 –60 –40 –20 0 20 40 60 TEMPERATURE (°C) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 V1 (V) 1 80 100 10m 1m 100µ 10p 3.5 V2 = 3V V1 = 5V 3.0 2.5 85°C – 40°C 2.5 VOL (V) VOL = 0.2V 3 VOH (V) 2.0 4 1µ V1 = 5V V2 = 3V V3 = 2.5V V4 = 1V 25°C VOL = 0.4V 5 100n RST High Level Output Voltage vs Output Source Current (LTC2902-2) 3.0 6 10n 1n CRT (FARAD) 2902 G17 RST, COMPX Voltage Output Low vs Output Sink Current TA = 25°C 7 100p 2902 G16 RST, COMPX ISINK vs Supply Voltage 8 TA = 25°C 100m 6.9 2902 G15 ISINK (mA) 140 RESET TIME-OUT PERIOD, tRST (sec) RESET TIME-OUT PERIOD, tRST (ms) V1 = V2 = V3 = V4 10k PULL-UP FROM RST TO V1 TA = 25°C 0 RESET OCCURS ABOVE CURVE 160 8.9 5 9 180 Reset Time-Out Period vs Temperature RST Output Voltage vs V1, VPG = 0V 4 TA = 25°C 200 2902 G14 2902 G13 RST OUTPUT VOLTAGE (V) TYPICAL TRANSIENT DURATION (µs) TYPICAL TRANSIENT DURATION (µs) IV4 (µA) 220 450 1.0 V1 = 5V 0.9 V2 = 3.3V V3 = 2.5V 0.8 V4 = 1.8V 0.7 10 Typical Transient Duration vs Comparator Overdrive (V3, V4) Typical Transient Duration vs Comparator Overdrive (V1, V2) IV4 vs Temperature 1.5 1.0 2.0 – 40°C 1.5 25°C 1.0 85°C 2 0.5 0.5 1 0 0 1 2 3 4 V1 OR V2 (V) 5 6 2902 G18 0 0 0 10 20 30 50 60 ISINK (mA) 40 70 80 90 2902 G19 0 0.5 1 1.5 ISOURCE (mA) 2 2.5 2902 G20 2902f 6 LTC2902 U W TYPICAL PERFOR A CE CHARACTERISTICS COMPX Propagation Delay vs Input Overdrive Above Threshold COMPX Pull-Up Current vs V2 (COMPX Held at 0V) 20 250 TA = 25°C COMPX PROPAGATION DELAY (µs) 18 PULL-UP CURRENT (µA) 16 14 12 10 8 6 4 2 0 1 1.5 2 2.5 4 3 3.5 V2 (V) 4.5 200 150 100 V1, V2 50 V3, V4 0 5 TA = 25°C 1000 10 100 INPUT OVERDRIVE ABOVE THRESHOLD (mV) 2902 G22 2902 G21 RST Pull-Up Current vs V2 (LTC2902-1) 20 RST Pull-Up Current vs V2 (LTC2902-2) 6 TA = 25°C TA = 25°C 18 5 PULL-UP CURRENT (mA) PULL-UP CURRENT (µA) 16 14 12 10 8 VRT33 6 VRT30 VRT25 4 4 3 VRT33 VRT30 2 VRT25 1 2 0 0 2 2.5 3 3.5 V2 (V) 4 4.5 5 2902 G23 2 2.5 3 3.5 V2 (V) 4 4.5 5 2902 G24 U U U 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. 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. 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. 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. V3 (Pin 3): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V or ADJ. See Table 1 for details. 2902f 7 LTC2902 U U U 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. 2902f 8 LTC2902 W BLOCK DIAGRA V1 V2 POWER DETECT VCC 6µA COMP1 – V2 2 + V2 – V1 4 V2 14 V3 6µA + COMP2 16 RESISTIVE DIVIDER MATRIX 3 – V4 13 + V2 6µA GND 10 COMP3 – + VPG 11 1 A/D V2 BUFFER 6µA VREF BANDGAP REFERENCE 12 COMP4 15 BUFFER GAIN ADJUST ADJUSTABLE RESET PULSE GENERATOR VCC V2 LTC2902-1 2µA 6µA 22µA RST 10µA 6 VCC 7 T0 9 T1 5 CRT 8 RDIS CRT LTC2902-2 V2 RST 6 2902 DB-1 2902f 9 LTC2902 U W U U 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. LTC2902 12 VREF 11 VPG 10 GND R1 1% R2 1% 2902 F04 Figure 4. Monitor Programming Table 1. Voltage Threshold Programming MODE V1 (V) V2 (V) V3 (V) V4 (V) R1 (kΩ) R2 (kΩ) VPG VREF 0 5.0 3.3 ADJ ADJ Open Short 0.000 1 5.0 3.3 ADJ –ADJ 93.1 9.53 0.094 2 3.3 2.5 ADJ ADJ 86.6 16.2 0.156 3 3.3 2.5 ADJ –ADJ 78.7 22.1 0.219 4 3.3 2.5 1.5 ADJ 71.5 28.0 0.281 5 5.0 3.3 2.5 ADJ 66.5 34.8 0.344 6 5.0 3.3 2.5 1.8 59.0 40.2 0.406 7 5.0 3.3 2.5 1.5 53.6 47.5 0.469 8 5.0 3.0 2.5 ADJ 47.5 53.6 0.531 9 5.0 3.0 ADJ ADJ 40.2 59.0 0.594 10 3.3 2.5 1.8 1.5 34.8 66.5 0.656 11 3.3 2.5 1.8 ADJ 28.0 71.5 0.719 12 3.3 2.5 1.8 –ADJ 22.1 78.7 0.781 13 5.0 3.3 1.8 –ADJ 16.2 86.6 0.844 14 5.0 3.3 1.8 ADJ 9.53 93.1 0.906 15 5.0 3.0 1.8 ADJ Short Open 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 10 LTC2902 U W U U APPLICATIO S I FOR ATIO Table 2. Suggested 1% Resistor Values for the ADJ Inputs VTRIP LTC2902 R3 1% + V3 OR V4 R4 1% – + – 0.5V 5% TOLERANCE MODE 2902 F05 Figure 5. Setting the Positive Adjustable Trip Point 12 R4 1% VREF 13 V4 R3 1% LTC2902 – + VSUPPLY (V) VTRIP (V) R3 (kΩ) R4 (kΩ) 12 11.25 2150 100 10 9.4 1780 100 8 7.5 1400 100 7.5 7 1300 100 6 5.6 1020 100 5 4.725 845 100 3.3 3.055 511 100 3 2.82 464 100 2.5 2.325 365 100 1.8 1.685 237 100 1.5 1.410 182 100 1.2 1.120 124 100 1 0.933 86.6 100 0.9 0.840 68.1 100 VTRIP Table 3. Suggested 1% Resistor Values for the –ADJ Input 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 VSUPPLY (V) VTRIP (V) R3 (kΩ) R4 (kΩ) –2 –1.87 187 121 –5 –4.64 464 121 –5.2 –4.87 487 121 –10 –9.31 931 121 –12 –11.30 1130 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 Tables 2 and 3 offer suggested 1% resistor values for various adjustable applications. 2902f 11 LTC2902 U W U U APPLICATIO S I FOR ATIO particular output is known, output fall time (10% to 90%) is estimated using: tFALL ≈ 2.2 • RPD • CLOAD 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 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 T1 TOLERANCE (%) VREF (V) Low Low 5 1.210 Low High 7.5 1.178 High Low 10 1.146 High High 12.5 1.113 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 12 LTC2902 U TYPICAL APPLICATIO S Quad Supply Monitor, 5% Tolerance 5V, 3V, 1.8V, 12V (ADJ) 1 2 1.8V 5V 3 4 5 SYSTEM RESET CRT 6 7 8 COMP3 COMP2 COMP1 COMP4 V3 V2 V1 LTC2902 V4 CRT VREF RST VPG T0 GND RDIS T1 16 15 14 3V 13 R3 2.15M 1% 12V VTRIP = 11.25V 12 11 R4 100k 1% 10 9 2902 TA02 5V, –5V Monitor with Unused V2, V3 Inputs Pulled Above Trip Thresholds (5% Tolerance) 1 2 3 5V 4 5 SYSTEM RESET CRT 6 7 8 COMP3 COMP2 COMP1 COMP4 V3 V2 V1 LTC2902 V4 CRT VREF RST VPG T0 RDIS GND T1 16 15 R3 464k 1% 14 13 –5V VTRIP = –4.64V 12 R1 R4 16.2k 121k 1% 1% 11 10 9 R2 86.6k 1% 2902 TA03 2902f 13 LTC2902 U TYPICAL APPLICATIO S Quad Supply Monitor with LED Undervoltage Indicators, 12.5% Tolerance, Reset Disabled 5V, 3.3V, 2.5V, 1.5V RL1 1k LED RL3 1k LED 1 2 2.5V 3 4 5V 5 6 7 CRT RL2 1k 8 LED COMP3 COMP2 COMP1 COMP4 V3 V2 V1 LTC2902 V4 CRT VREF RST VPG T0 GND RDIS T1 RL4 1k LED 16 15 14 3.3V 13 1.5V 12 R1 53.6k 1% 11 10 9 R2 47.5k 1% 2902 TA04 2902f 14 LTC2902 U PACKAGE DESCRIPTIO GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .189 – .196* (4.801 – 4.978) .045 ±.005 16 15 14 13 12 11 10 9 .254 MIN .009 (0.229) REF .150 – .165 .229 – .244 (5.817 – 6.198) .0165 ± .0015 .150 – .157** (3.810 – 3.988) .0250 TYP RECOMMENDED SOLDER PAD LAYOUT 1 .015 ± .004 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) 2 3 4 5 6 7 .053 – .068 (1.351 – 1.727) 8 .004 – .0098 (0.102 – 0.249) 0° – 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) .008 – .012 (0.203 – 0.305) .0250 (0.635) BSC 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 GN16 (SSOP) 0502 2902f 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. 15 LTC2902 U TYPICAL APPLICATIO Quad Supply Monitor with Hysteresis 5% Tolerance (Supplies Rising) 12.5% Tolerance (After RST Goes High) 5V 4 3.3V 14 3 2.5V 1.8V 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 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65V Threshold LTC694-3.3 3.3V Supply Monitor, Watchdog Timer and Battery Backup 2.9V Threshold LTC699 5V Supply Monitor and Watchdog Timer 4.65V Threshold LTC1232 5V Supply Monitor, Watchdog Timer and Push-Button Reset 4.37V/4.62V Threshold LTC1326 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%) LTC1536 Precision Triple Supply Monitor for PCI Applications Meets PCI tFAIL Timing Specifications 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 LTC1727-2.5/LTC1727-5 Micropower Triple Supply Monitor with Open-Drain Reset Individual Monitor Outputs in MSOP LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitor with Open-Drain Reset 5-Lead SOT-23 Package LTC1728-2.5/LTC1728-5 Micropower Triple Supply Monitor with Open-Drain Reset 5-Lead SOT-23 Package LTC1985-1.8 Micropower Triple Supply Monitor with Push-Pull Reset Output 5-Lead SOT-23 Package LTC2900 Programmable Quad Supply Monitor Adjustable RESET, 10-Lead MSOP Package LTC2901 Programmable Quad Supply Monitor Adjustable RESET and Watchdog Timer, 16-Lead SSOP Package 2902f 16 Linear Technology Corporation LT/TP 1002 2K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com  LINEAR TECHNOLOGY CORPORATION 2002