LTC2900 Programmable Quad Supply Monitor with Adjustable Reset Timer U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO 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 U APPLICATIO S ■ ■ ■ ■ 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. 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®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. TYPICAL APPLICATIO Quad Supply Monitor (5V, 3.3V, 2.5V, 1.8V) 5V 3.3V DC/DC CONVERTER SYSTEM LOGIC 2.5V 1.8V C1 0.1µF C2 0.1µF R1 59k 1% R2 40.2k 1% V3 V4 V1 LTC2900-2 V2 VREF VPG GND RST PBR CRT CRT 47nF PUSH-BUTTON RESET 2900 TA01 tRST = 216ms 2900f 1 LTC2900 W W W AXI U U ABSOLUTE RATI GS (Notes 1, 2, 3) 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 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 U U W PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER ORDER PART NUMBER TOP VIEW TOP VIEW V3 V1 CRT RST PBR 10 9 8 7 6 1 2 3 4 5 V2 V4 VREF VPG GND MS PACKAGE 10-LEAD PLASTIC MSOP LTC2900-1CMS LTC2900-2CMS LTC2900-1IMS LTC2900-2IMS V3 1 10 V2 V1 2 9 V4 CRT 3 8 VREF RST 4 7 VPG PBR 5 6 GND LTC2900-1CDD LTC2900-2CDD LTC2900-1IDD LTC2900-2IDD MS PART MARKING TJMAX = 125°C, θJA = 250°C/W LTYJ LTYL LTYK LTYM DD PART MARKING DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN LABU LABW LABV LABX TJMAX = 125°C, θJA = 43°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 V1 Input Threshold ● 4.600 4.675 4.750 V VRT33 3.3V, 5% Reset Threshold V1, V2 Input Threshold ● 3.036 3.086 3.135 V VRT30 3V, 5% Reset Threshold V2 Input Threshold ● 2.760 2.805 2.850 V VRT25 2.5V, 5% Reset Threshold V2, V3 Input Threshold ● 2.300 2.338 2.375 V VRT18 1.8V, 5% Reset Threshold V3, V4 Input Threshold ● 1.656 1.683 1.710 V VRT15 1.5V, 5% Reset Threshold V3, V4 Input Threshold ● 1.380 1.403 1.425 V VRTA ADJ Reset Threshold V3, V4 Input Threshold ● 0.492 0.500 0.508 VRTAN – ADJ Reset Threshold V4 Input Threshold ● – 18 0 18 mV VCC Minimum Internal Operating Voltage RST in Correct Logic State, VCC Rising Prior to Program ● 1 V VCCMINP Minimum Required for Programming VCC Rising ● 2.42 V VREF Reference Voltage VCC ≥ 2.3V, IVREF = ±1mA, CREF ≤ 1000pF ● 1.192 1.228 V VPG Programming Voltage Range VCC ≥ VCCMINP ● 0 VREF V IVPG VPG Input Current VPG = VREF ● IV1 V1 Input Current V1 = 5V, IVREF = 12µA, (Note 4) ● 1.210 43 V ±20 nA 75 µA 2900f 2 LTC2900 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 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 –15 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 MIN TYP MAX UNITS 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 VX Less Than Reset Threshold VRTX by More Than 1% VOL Output Voltage Low RST 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 Output Voltage High RST (LTC2900-1) (Note 5) ISOURCE = 1µA ● V2 – 1 V Output Voltage High RST (LTC2900-2) (Note 6) ISOURCE = 200µA ● 0.8 • V2 V VOH µs 150 Manual Reset Pin VIH PBR Input Threshold High VCC = 3.3V to 5.5V ● VIL PBR Input Threshold Low VCC = 3.3V to 5.5V ● 0.4 1.6 tPBW PBR Input Pulse Width VCC = 3.3V ● 150 tPBD Manual Reset Propagation Delay VCC = 3.3V, VPBR Falling ● IPBR PBR Pull-Up Current VPBR = 0V V ns 0.1 1 µs µA –10 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 V 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 LTC2900-1 ISOURCE 1µA 2900 F01 Figure 1. RST VOH Test V1 V2 V3 V4 RST 2900 F02 Figure 2. RST VOL Test ISINK 2.5mA, 100µA V1 V2 V3 V4 LTC2900-2 RST ISOURCE 200µA 2900 F03 Figure 3. Active Pull-Up RST VOH Test 2900f 3 LTC2900 WU W TI I G DIAGRA Monitor Timing VX VRTX tPBD tRST tUV tRST 1.5V RST 2900 TD PBR tPBW U W TYPICAL PERFOR A CE CHARACTERISTICS 5V Threshold Voltage vs Temperature 3.3V Threshold Voltage vs Temperature THESHOLD VOLTAGE, VRT50 (V) 4.725 4.700 4.675 4.650 4.625 3.135 2.850 3.125 2.840 THRESHOLD VOLTAGE, VRT30 (V) THRESHOLD VOLTAGE, VRT33 (V) 4.750 3V Threshold Voltage vs Temperature 3.115 3.105 3.095 3.085 3.075 3.065 3.055 3.035 –60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 2.810 2.800 2.790 2.780 80 2.760 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 2900 G02 2900 G01 2.5V Threshold Voltage vs Temperature 1.425 1.705 1.420 2.3450 2.3375 2.3300 2.3225 2.3150 2.3075 2.3000 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) THRESHOLD VOLTAGE, VRT15 (V) 1.710 2.3675 2.3525 1.700 1.695 1.690 1.685 1.680 1.675 1.670 1.665 100 2900 G04 1.655 –60 –40 –20 0 20 40 60 TEMPERATURE (°C) 1.415 1.410 1.405 1.400 1.395 1.390 1.385 1.660 80 100 1.5V Threshold Voltage vs Temperature 2.3750 2.3600 80 2900 G03 1.8V Threshold Voltage vs Temperature THRESHOLD VOLTAGE, VRT18 (V) THRESHOLD VOLTAGE, VRT25 (V) 2.820 2.770 3.045 4.600 20 40 60 –60 –40 –20 0 TEMPERATURE (°C) 2.830 80 100 2900 G05 1.380 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 2900 G06 2900f 4 LTC2900 U W TYPICAL PERFOR A CE CHARACTERISTICS ADJ Threshold Voltage vs Temperature – ADJ Threshold Voltage vs Temperature 0.504 0.502 0.500 0.498 0.496 0.494 0.492 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 1.228 0.012 1.222 0.006 1.216 VREF (V) 0.506 THRESHOLD VOLTAGE, VRTAN (V) 0 1.204 –0.012 1.198 –0.018 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 2900 G07 IV1 vs Temperature 1.192 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 IV2 vs Temperature V1 = 5V 1.4 V2 = 3.3V V3 = 2.5V 1.3 V4 = 1.8V 1.2 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 90 V2 = 3.3V V3 = 2.5V 80 V4 = 1.8V 70 40 1.0 0.9 0.6 0.5 30 0.8 0.4 20 0.7 0.3 10 0 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 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) 2900 G09 100 450 TYPICAL TRANSIENT DURATION (µs) 0.6 0.5 0.4 0.3 0.2 0.1 80 100 2900 G12 350 300 RESET OCCURS ABOVE CURVE 250 200 150 100 50 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 2900 G13 100 Typical Transient Duration vs Comparator Overdrive (V3, V4) 220 TA = 25°C 400 80 2900 G11 Typical Transient Duration vs Comparator Overdrive (V1, V2) 1.0 V1 = 5V 0.9 V2 = 3.3V V3 = 2.5V 0.8 V4 = 1.8V 0.7 0 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 2900 G10 IV4 vs Temperature 100 IV3 vs Temperature 1.1 50 80 2900 G21 1.5 IV2 (µA) IV1 (µA) 80 2900 G08 100 IV4 (µA) 1.210 –0.006 TYPICAL TRANSIENT DURATION (µs) THRESHOLD VOLTAGE, VRTA (V) 0.508 VREF vs Temperature 0.018 200 180 160 TA = 25°C RESET OCCURS ABOVE CURVE 140 120 100 80 60 40 20 0 1 10 100 0.1 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 2900 G20 2900f 5 LTC2900 U W TYPICAL PERFOR A CE CHARACTERISTICS RST Output Voltage vs V1, VPG = 0V Reset Time-Out Period vs Temperature 8.9 5 3 2 1 0 0 10 CRT = 1500pF 8.4 (SILVER MICA) 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 4 RST OUTPUT VOLTAGE (V) Reset Time-Out Period vs Capacitance 7.9 7.4 6.4 5.9 5.4 80 2900 G14 1m 100µ 10p 100 100p 10n 1n CRT (FARAD) 100n RST High Level Output Voltage vs Output Source Current (LTC2900-2) 3.0 3.5 V2 = 3V V1 = 5V 3.0 – 40°C 85°C 2.5 VOH (V) 2.0 1.5 1.0 VOL = 0.2V V1 = 5V V2 = 3V V3 = 2.5V V4 = 1V 25°C 2.5 VOL = 0.4V 1µ 2900 G16 RST Voltage Output Low vs Output Sink Current VOL (V) ISINK (mA) 10m 2900 G15 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 1 100m 6.9 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) TA = 25°C 2.0 – 40°C 1.5 25°C 1.0 85°C 0.5 2 3 4 V1 OR V2 (V) 5 0 6 0.5 0 0 10 20 30 70 50 60 ISINK (mA) 40 80 2900 G17 1 1.5 ISOURCE (mA) 2 2.5 2900 G19 RST Pull-Up Current vs V2 (LTC2900-2) 6 TA = 25°C TA = 25°C 18 5 PULL-UP CURRENT (mA) 16 PULL-UP CURRENT (µA) 0.5 2900 G18 RST Pull-Up Current vs V2 (LTC2900-1) 20 0 90 14 12 10 8 VRT33 6 VRT30 VRT25 4 4 3 VRT33 VRT30 2 VRT25 1 2 0 2 2.5 3 3.5 V2 (V) 4 4.5 5 2900 G22 0 2 2.5 3 3.5 V2 (V) 4 4.5 5 2900 G23 2900f 6 LTC2900 U U U 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. 2900f 7 LTC2900 W BLOCK DIAGRA V1 – POWER DETECT + VCC V2 – V1 2 V2 10 + RESISTIVE DIVIDER MATRIX V3 1 – V4 9 + LTC2900-1 V2 6µA GND 6 RST – 4 ADJUSTABLE RESET PULSE GENERATOR + VPG 2µA A/D 7 BUFFER VREF 8 VCC 1.210V V2 22µA BANDGAP REFERENCE RST 10µA 4 VCC PBR 5 LTC2900-2 3 CRT CRT 2900 DB-1 2900f 8 LTC2900 U W U U APPLICATIO S I FOR ATIO Table 1. Voltage Threshold Programming 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. 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 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 U W U U APPLICATIO S I FOR ATIO VTRIP 8 LTC2900 R3 1% R4 1% + V3 OR V4 VREF 9 V4 R3 1% R4 1% – + – LTC2900 – + VTRIP 0.5V 2900 F06 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. Figure 6. Setting the Negative Adjustable Trip Point Table 2. Suggested 1% Resistor Values for the ADJ Inputs 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 Table 3. Suggested 1% Resistor Values for the –ADJ Input 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 2900f 10 LTC2900 U W U U 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: 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 11 LTC2900 U W U U 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. U TYPICAL APPLICATIO S Quad Supply Monitor with Push-Button Reset 5V, 3V, 1.8V, 12V (ADJ) 1.8V 5V 1 2 V3 V2 V1 V4 10 3V 9 R3 2.15M 1% LTC2900 8 VREF CRT 4 7 RST VPG 6 5 PBR GND 3 SYSTEM RESET CRT 12V VTRIP = 11.25V R4 100k 1% NORMALLY OPEN 2900 TA02 5V, – 5V Monitor and Unused V2, V3 Inputs Pulled Above Trip Thresholds 1 5V V3 V2 9 V4 LTC2900 8 VREF CRT 4 7 VPG RST 5 6 GND PBR 2 R3 464k 1% 10 V1 –5V VTRIP = –4.64V 3 SYSTEM RESET CRT R1 R4 16.2k 121k 1% 1% R2 86.6k 1% 2900 TA03 2900f 12 LTC2900 U 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% 1 V2 10 3.3V 9 V4 V1 LTC2900-1 8 VREF CRT 4 7 RST VPG 6 5 PBR GND 2 5V RL1 1k SYSTEM RESET V3 CRT LED 10k* R3 487k 1% R4 121k 1% R1 93.1k 1% R2 9.53k 1% 3 MANUAL RESET BUTTON (NORMALLY OPEN) *OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE –5.2V VTRIP = –4.87V 2900 TA05 Low Voltage Quad Supply Monitor 3.3V, 2.5V, 1V (ADJ), 0.9V (ADJ) R5 86.6k 1% 1V VTRIP = 0.933V 1 3.3V V3 V2 10 9 V4 LTC2900 8 VREF CRT 4 7 RST VPG 5 6 PBR GND 2 R3 68.1k 1% 2.5V V1 0.9V VTRIP = 0.84V 3 R6 100k 1% SYSTEM RESET CRT R1 86.6k 1% R2 16.2k 1% R4 100k 1% 2900 TA04 2900f 13 LTC2900 U PACKAGE DESCRIPTIO DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) 0.675 ±0.05 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) R = 0.115 TYP RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.10 (4 SIDES) 0.38 ± 0.10 6 10 5 1 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 5) 0.200 REF (DD10) DFN 0403 0.75 ±0.05 0.00 – 0.05 0.25 ± 0.05 0.50 BSC 2.38 ±0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD 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 2900f 14 LTC2900 U PACKAGE DESCRIPTIO MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.2 – 3.45 (.126 – .136) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.50 0.305 ± 0.038 (.0197) (.0120 ± .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 0.497 ± 0.076 (.0196 ± .003) REF 10 9 8 7 6 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.90 ± 0.15 (1.93 ± .006) DETAIL “A” 0° – 6° TYP GAUGE PLANE 1 2 3 4 5 0.53 ± 0.01 (.021 ± .006) DETAIL “A” 1.10 (.043) MAX 0.86 (.034) REF 0.18 (.007) SEATING PLANE 0.17 – 0.27 (.007 – .011) TYP 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 0.13 ± 0.076 (.005 ± .003) MSOP (MS) 0802 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 U 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% MASTER RESET R3B 464k 1% –5V 2.5V 1V R3A 2150k 1% 3V 1 12V 5V V3 V2 10 9 V4 V1 LTC2900-2 8 VREF CRT 4 7 RST VPG 5 6 PBR GND 1 1.8V 2 R6A 100k 1% CRTA 20k V2 R4B 121k 1% 10 9 V4 V1 LTC2900-2 8 VREF CRT 4 7 RST VPG 6 5 PBR GND 2 3.3V 3 3 R4A 100k 1% V3 R1A 40.2k 1% CRTB R2A 59k 1% R1B 22.1k 1% R2B 78.7k 1% 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 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 LTC2902 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 2900f 16 Linear Technology Corporation LT/TP 0403 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