LTC2900

LTC2900 Programmable Quad Supply Monitor with Adjustable Reset Timer FEATURES s s DESCRIPTIO 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 Low Supply Current: 43µA Typ Adjustable Reset Time Small MSOP and 3mm × 3mm DFN Packages 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®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 43µA 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 and the 10-lead 3mm × 3mm DFN packages. , LTC and LT are registered trademarks of Linear Technology Corporation. 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 (5V, 3.3V, 2.5V, 1.8V) 5V 3.3V DC/DC CONVERTER 2.5V 1.8V V3 V4 V1 LTC2900-2 V2 VREF VPG GND RST PBR CRT CRT 47nF tRST = 216ms 2900f C1 0.1µF C2 0.1µF R1 59k 1% R2 40.2k 1% PUSH-BUTTON RESET 2900 TA01 U SYSTEM LOGIC U U 1 LTC2900 ABSOLUTE AXI U RATI GS V1, V2, V3, V4, VPG, PBR ............................. – 0.3V to 7V RST (LTC2900-1)........................................ – 0.3V to 7V RST (LTC2900-2).......................... – 0.3V to (V2 + 0.3V) CRT ............................................. – 0.3V to (VCC + 0.3V) VREF ............................................. – 0.3V to (VCC + 0.3V) Reference Load Current (IVREF) ............................ ±1mA PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW TOP VIEW V3 V1 CRT RST PBR 1 2 3 4 5 10 9 8 7 6 V2 V4 VREF VPG GND LTC2900-1CMS LTC2900-2CMS LTC2900-1IMS LTC2900-2IMS MS PART MARKING LTYJ LTYL LTYK LTYM MS PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 250°C/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 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 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 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 = 12µA, (Note 4) q q q q q q q q q q q q q q 2 U U W WW U W (Notes 1, 2, 3) V4 Input Current (– ADJ Mode) ............................ – 1mA Operating Temperature Range LTC2900-1C/LTC2900-2C ....................... 0°C to 70°C LTC2900-1I/LTC2900-2I .................... –40°C to 85°C Storage Temperature Range .................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................... 300°C ORDER PART NUMBER V3 V1 CRT RST PBR 1 2 3 4 5 10 V2 9 V4 8 VREF 7 VPG 6 GND LTC2900-1CDD LTC2900-2CDD LTC2900-1IDD LTC2900-2IDD DD PART MARKING DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 43°C/W LABU LABW LABV LABX 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 µA 2900f 1.192 0 1.210 1.228 VREF ± 20 43 75 LTC2900 ELECTRICAL CHARACTERISTICS SYMBOL IV2 IV3 IV4 PARAMETER 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 = 25°C. VCC = 5V, unless otherwise noted. (Note 3) CONDITIONS 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 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 q q q q q q q q q MIN TYP 0.8 0.52 MAX 2 1.2 15 0.8 15 15 –2.6 30 9 UNITS µA µA nA µA nA nA µA µA ms µs –15 0.34 –15 –15 –1.4 10 5 –2 20 7 150 0.15 0.05 0.05 V2 – 1 0.8 • V2 ICRT(UP) ICRT(DN) tRST tUV VOL CRT Pull-Up Current CRT Pull-Down Current Reset Time-Out Period VX Undervoltage Detect to RST Output Voltage Low RST 0.4 0.3 0.3 V V V V V ISOURCE = 1µA ISOURCE = 200µA 1.6 0.4 150 0.1 –10 1 V V ns µs µA Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: All currents into pins are positive, all voltages are referenced to GND unless otherwise noted. 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 6µA. 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 1µA 2900 F01 LTC2900-1 V1 V2 V3 V4 2900 F02 RST ISINK 2.5mA, 100µA V1 V2 V3 V4 LTC2900-2 RST ISOURCE 200µA 2900 F03 Figure 1. RST VOH Test Figure 2. RST VOL Test Figure 3. Active Pull-Up RST VOH Test 2900f 3 LTC2900 TI I G DIAGRA VX VRTX tUV tRST 1.5V tPBD tRST RST PBR tPBW TYPICAL PERFOR A CE CHARACTERISTICS 5V Threshold Voltage vs Temperature 4.750 THRESHOLD VOLTAGE, VRT33 (V) 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 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) 4 UW W Monitor Timing 2900 TD UW 3.3V Threshold Voltage vs Temperature 3.135 3.125 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 1.710 1.705 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 2900f LTC2900 TYPICAL PERFOR A CE CHARACTERISTICS 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 0.018 0.012 0.006 0 –0.006 –0.012 –0.018 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) VREF (V) IV1 vs Temperature 100 V1 = 5V 90 V2 = 3.3V V3 = 2.5V 80 V4 = 1.8V 70 IV1 (µA) IV2 (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 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 UW 2900 G09 2900 G12 – ADJ Threshold Voltage vs Temperature 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 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 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) 2900 G20 TA = 25°C RESET OCCURS ABOVE CURVE 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 2900 G13 2900f 5 LTC2900 TYPICAL PERFOR A CE CHARACTERISTICS RST Output Voltage vs V1, VPG = 0V 5 8.9 RST OUTPUT VOLTAGE (V) 4 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 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) 2900 G14 RST, ISINK vs Supply Voltage 13 T = 25°C 12 A 11 10 9 8 7 6 5 4 3 2 1 0 1 0 3.0 VOL = 0.4V VOL (V) ISINK (mA) 1.5 1.0 0.5 0 VOH (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 (µA) TA = 25°C 14 12 10 8 6 4 2 0 2 2.5 3 3.5 V2 (V) 4 4.5 5 2900 G22 PULL-UP CURRENT (mA) VRT30 VRT25 6 UW 5 2900 G17 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 Reset Time-Out Period vs Capacitance 10 TA = 25°C 1 100m 10m 1m 100µ 10p 100p 10n 1n CRT (FARAD) 100n 1µ 2900 G16 2900 G15 RST Voltage Output Low vs Output Sink Current V2 = 3V V1 = 5V 2.5 2.0 85°C 3.5 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 RST High Level Output Voltage vs Output Source Current (LTC2900-2) V1 = 5V V2 = 3V V3 = 2.5V V4 = 1V – 40°C 25°C 85°C 6 0 0.5 1 1.5 ISOURCE (mA) 2 2.5 2900 G19 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 = 25°C VRT33 VRT33 VRT30 VRT25 2900f LTC2900 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 device. Bypass this pin to ground with a 0.1µF (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 50µs. 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 the programmed delay time after all voltage inputs are above threshold. May be pulled above V2 using an external pull-up (LTC2900-1 only). PBR (Pin 5): Manual Reset Pin. Attach a 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 device. Bypass this pin to ground with a 0.1µF (or greater) capacitor. RST is weakly pulled up to V2 (LTC2900-1). RST is actively pulled up to V2 in the LTC2900-2. U U U 2900f 7 LTC2900 BLOCK DIAGRA V3 1 V4 9 GND 6 RESISTIVE DIVIDER MATRIX VPG 7 A/D BUFFER VREF 8 1.210V 8 + V2 10 + + – V1 2 + – – – W V1 POWER DETECT VCC V2 LTC2900-1 V2 6µA RST 4 ADJUSTABLE RESET PULSE GENERATOR VCC 2µA 22µA BANDGAP REFERENCE 10µA VCC PBR 5 3 CRT CRT 2900 DB-1 LTC2900-2 V2 RST 4 2900f 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 (1kΩ 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 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. U 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 W UU 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 2900f 9 LTC2900 APPLICATIO S I FOR ATIO VTRIP R3 1% V3 OR V4 R4 1% LTC2900 + R3 1% – + – 0.5V 2900 F05 Figure 5. Setting the Positive Adjustable Trip Point 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). 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. 10 U 8 R4 1% VREF LTC2900 9 V4 W UU – + VTRIP 2900 F06 Figure 6. Setting the Negative Adjustable Trip Point 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 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 2900f LTC2900 APPLICATIO S I FOR ATIO 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 device. 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 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 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: U 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 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 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. 2900f W UU 11 LTC2900 APPLICATIO S I FOR ATIO Ensuring Reset Valid for VCC Down to 0V (LTC2900-2) Some applications require the reset output (RST) to be valid with VCC down to 0V. The LTC2900-2 is designed to handle this requirement with the addition of an external resistor from RST to ground. The resistor will provide a path for stray charge and/or leakage currents, preventing the RST output from floating to undetermined voltages when connected to high impedance (such as CMOS logic inputs). The resistor value should be small enough to provide effective pull-down without excessively loading the active 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. 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 12 U LTC2900 8 VREF CRT 4 7 RST VPG 6 5 PBR GND 2900 TA02 W U UU 1 2 3 V3 V1 V2 10 9 V4 LTC2900 8 VREF CRT 4 7 VPG RST 5 6 GND PBR 2900f 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 Low Voltage Quad Supply Monitor 3.3V, 2.5V, 1V (ADJ), 0.9V (ADJ) R5 86.6k 1% 1V VTRIP = 0.933V 3.3V SYSTEM RESET CRT R3 68.1k 1% 0.9V VTRIP = 0.84V R1 86.6k 1% R2 16.2k 1% U 1 2 3 V3 V2 10 3.3V 10k* 9 V4 V1 LTC2900-1 8 VREF CRT 4 7 RST VPG 6 5 PBR GND –5.2V VTRIP = – 4.87V MANUAL RESET BUTTON (NORMALLY OPEN) *OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE 1 2 3 V3 V1 V2 10 2.5V R6 100k 1% 9 V4 LTC2900 8 VREF CRT 4 7 RST VPG 5 6 PBR GND R4 100k 1% 2900 TA04 2900f 13 LTC2900 PACKAGE DESCRIPTIO 3.50 ± 0.05 1.65 ± 0.05 2.15 ± 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.38 ± 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 6 10 0.38 ± 0.10 PIN 1 TOP MARK (SEE NOTE 5) 5 0.200 REF 0.75 ± 0.05 2.38 ± 0.10 (2 SIDES) 1 NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. ALL DIMENSIONS ARE IN MILLIMETERS 3. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 4. EXPOSED PAD SHALL BE SOLDER PLATED 5. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 14 U DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) 0.675 ± 0.05 3.00 ± 0.10 (4 SIDES) 1.65 ± 0.10 (2 SIDES) (DD10) DFN 0403 0.25 ± 0.05 0.50 BSC 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD 2900f LTC2900 PACKAGE DESCRIPTIO U 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 12345 0.53 ± 0.01 (.021 ± .006) DETAIL “A” 0.18 (.007) SEATING PLANE 0.17 – 0.27 (.007 – .011) TYP 0.13 ± 0.076 (.005 ± .003) MSOP (MS) 0802 5.23 (.206) MIN 0.50 0.305 ± 0.038 (.0197) (.0120 ± .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) GAUGE PLANE 4.90 ± 0.15 (1.93 ± .006) 3.00 ± 0.102 (.118 ± .004) NOTE 4 1.10 (.043) MAX 0.86 (.034) REF 0.50 (.0197) NOTE: BSC 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 2900f 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 LTC2900 TYPICAL APPLICATIO Monitor Eight Supplies Using Supervisory Cascade 12V (ADJ), 5V, 3.3V, 3V, 2.5V, 1.8V, 1V (ADJ), – 5V (– ADJ) R5A 86.6k 1% 1V R3A 2150k 1% 12V 5V R4A 100k 1% R6A 100k 1% CRTA 20k 3V 1 2 3 V3 V2 10 9 V4 V1 LTC2900-2 8 VREF CRT 4 7 RST VPG 5 6 PBR GND –5V 2.5V 1.8V 3.3V R1A 40.2k 1% R2A 59k 1% 1 2 3 V3 V2 10 9 V4 V1 LTC2900-2 8 VREF CRT 4 7 RST VPG 6 5 PBR GND 100k 2900 TA06 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 LTC2901 LTC2902 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 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 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%) 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 Adjustable Reset and Watchdog Timers, 16-Lead Narrow SSOP Package Adjustable Reset Timer, Supply Tolerance and Margining Functions, 16-Lead Narrow SSOP Package 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 q FAX: (408) 434-0507 q U R3B 464k 1% MASTER RESET R4B 121k 1% CRTB R1B 22.1k 1% R2B 78.7k 1% 2900f LT/TP 0403 2K • PRINTED IN USA www.linear.com © LINEAR TECHNOLOGY CORPORATION 2002