LTC2903CS6-B1#TRMPBF

LTC2903-1 Precision Quad Supply Monitor in 6-Lead SOT-23 U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Ultralow Voltage Reset: VCC = 0.5V Guaranteed Monitor Four Inputs Simultaneously 3.3V, 2.5V, 1.8V, ADJ (LTC2903-A1) 5V, 3.3V, 2.5V, 1.8V (LTC2903-B1) 5V, 3.3V, 1.8V, –5.2V (LTC2903-C1) 3.3V, ADJ, ADJ, ADJ (LTC2903-D1) 5V, ADJ, ADJ, ADJ (LTC2903-E1) Guaranteed Threshold Accuracy: ±1.5% of Monitored Voltage over Temperature 10% (A1, B1, C1) and 5% (D1, E1) Undervoltage Monitoring Low Supply Current: 20µA Typical 200ms Reset Time Delay Active Low Open-Drain RST Output Power Supply Glitch Immunity Low Profile (1mm) SOT-23 (ThinSOTTM) Package The LTC®2903-1 monitors up to four supply voltages. The common reset output remains low until all four inputs have been in compliance for 200ms. Voltage thresholds maintain ±1.5% accuracy over temperature (with respect to the monitored voltage). The LTC2903-1 features an open-drain RST output with a weak internal pullup. Internal supply voltage (VCC) is generated from the greater voltage on the V1, V2 inputs. VCC = V1 for LTC2903-D1 and LTC2903-E1. The RST output is guaranteed to sink at least 5µA (VOL = 0.15V) for VCC down to 0.5V and will typically conduct current down to 0V. Quiescent current is 20µA typical, making the LTC2903-1 ideal for power conscious systems. The LTC2903-1 is available in a 6-lead low profile (1mm) SOT-23 package. , LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. U APPLICATIO S ■ ■ ■ Multivoltage Systems Optical Networking Systems Cell Phone Base Stations Network Servers U ■ TYPICAL APPLICATIO Low Voltage Reset Pull-Down Performance vs External Pull-Up Current and Input Supply Voltage 0.10 5V VIN = V1 = V2 = V3 LTC2903-B1 0.09 DC/DC 2.5V CONVERTER 1.8V SYSTEM LOGIC C1 0.1µF C2 0.1µF LTC2903-B1 RST V1 GND V4 V2 V3 0.08 RESET PIN VOLTAGE (V) 3.3V 0.07 20µA 0.06 10µA 0.05 0.04 5µA 0.03 0.02 2903 TA01 0.01 0 2µA 1µA 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 VIN, INPUT SUPPLY VOLTAGE (V) 1 2903 TA01b 29031f a 1 LTC2903-1 U W U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Notes 1, 2, 3) V1, V2 ...................................................... – 0.3V to 6.5V V3 ................................................. 2.7V or (VCC + 0.3V) V4 (LTC2903-A1, -B1, -D1, -E1) ...............– 0.3V to 6.5V V4 (LTC2903-C1) .................................... – 6.5V to 0.3V RST ........................................................ – 0.3V to 6.5V Operating Temperature Range LTC2903C-X1 .......................................... 0°C to 70°C LTC2903I-X1 ...................................... – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C TOP VIEW 6 RST V1 1 GND 2 5 V4 V2 3 4 V3 S6 PACKAGE 6-LEAD PLASTIC TSOT-23 TJMAX = 125°C, θJA = 230°C/W ORDER PART NUMBER S6 PART MARKING LTC2903CS6-A1 LTC2903CS6-B1 LTC2903CS6-C1 LTC2903CS6-D1 LTC2903CS6-E1 LTC2903IS6-A1 LTC2903IS6-B1 LTC2903IS6-C1 LTC2903IS6-D1 LTC2903IS6-E1 LTAFV LTAJN LTAJQ LTBMX LTBMZ LTAFW LTAJP LTAJR LTBMY LTBNB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS (LTC2903-A1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT33 3.3V, 10% Reset Threshold V1 Input Threshold ● 2.871 2.921 2.970 V VRT25 2.5V, 10% Reset Threshold V2 Input Threshold ● 2.175 2.213 2.250 V VRT18 1.8V, 10% Reset Threshold V3 Input Threshold ● 1.566 1.593 1.620 V VRTA Adjustable Reset Threshold V4 Input Threshold ● 0.492 0.500 0.508 V (LTC2903-B1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT50 5V, 10% Reset Threshold V1 Input Threshold VRT33 3.3V, 10% Reset Threshold V2 Input Threshold ● 4.350 4.425 4.500 V ● 2.871 2.921 2.970 VRT25 2.5V, 10% Reset Threshold V V3 Input Threshold ● 2.175 2.213 2.250 V VRT18 1.8V, 10% Reset Threshold V4 Input Threshold ● 1.566 1.593 1.620 V (LTC2903-C1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT50 5V, 10% Reset Threshold V1 Input Threshold VRT33 3.3V, 10% Reset Threshold V2 Input Threshold ● 4.350 4.425 4.500 V ● 2.871 2.921 2.970 V VRT18 1.8V, 10% Reset Threshold V3 Input Threshold ● VRT52N –5.2V, 10% Reset Threshold V4 Input Threshold ● 1.566 1.593 1.620 V –4.524 –4.602 –4.680 V 29031f a 2 LTC2903-1 ELECTRICAL CHARACTERISTICS (LTC2903-D1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT33 3.3V, 5% Reset Threshold V1 Input Threshold ● 3.036 3.086 3.135 V VRTAV2 V2 Adjustable Threshold V2 Input Threshold ● 0.492 0.500 0.508 V VRTAV3 V3 Adjustable Threshold V3 Input Threshold ● 0.492 0.500 0.508 V VRTAV4 V4 Adjustable Threshold V4 Input Threshold ● 0.492 0.500 0.508 V (LTC2903-E1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT50 5V, 5% Reset Threshold V1 Input Threshold ● 4.600 4.675 4.750 V VRTAV2 V2 Adjustable Threshold V2 Input Threshold ● 0.492 0.500 0.508 V VRTAV3 V3 Adjustable Threshold V3 Input Threshold ● 0.492 0.500 0.508 V VRTAV4 V4 Adjustable Threshold V4 Input Threshold ● 0.492 0.500 0.508 V The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V unless otherwise noted. SYMBOL PARAMETER CONDITIONS IV1 V1 Input Current (Note 4) V1 = 3.3V (LTC2903-A1, LTC2903-D1) V1 = 5V (LTC2903-B1, LTC2903-C1, LTC2903-E1) IV2 MIN TYP MAX ● ● 20 25 80 80 µA µA V2 Input Current (Note 4) V2 = 2.5V (LTC2903-A1) ● V2 = 3.3V (LTC2903-B1, LTC2903-C1) ● V2 = 0.55V (LTC2903-D1, LTC2903-E1) ● 8 10 30 30 ±30 µA µA nA IV3 V3 Input Current V3 = 1.8V (LTC2903-A1, LTC2903-C1) ● V3 = 2.5V (LTC2903-B1) ● V3 = 0.55V (LTC2903-D1, LTC2903-E1) ● 8 10 30 30 ±30 µA µA nA IV4 V4 Input Current V4 = 0.55V (LTC2903-A1) V4 = 1.8V (LTC2903-B1) V4 = –5.2V (LTC2903-C1) V4 = 0.55V (LTC2903-D1, LTC2903-E1) 2 –3 ±30 4 –6 ±30 nA µA µA nA 200 260 ms ● ● ● ● ● tRST Reset Time-Out Period tUV VX Undervoltage Detect to RST VX Less Than Threshold VRTX by More Than 1% VOH Output Voltage High RST (LTC2903-1) (Note 5) IRST(DN) = –1µA (LTC2903-A1, LTC2903-B1, LTC2903-C1) (LTC2903-D1, LTC2903-E1) ● V2 – 1 V ● V1 – 1 V VCC = 0.2V, IRST = 0.1µA VCC = 0.5V, IRST = 5µA VCC = 1V, IRST = 200µA VCC = 3V, IRST = 2500µA ● ● ● ● VOL Output Voltage Low RST (Note 6) Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: All currents into pins are positive, all voltages are referenced to GND unless otherwise noted. Note 3: The internal supply voltage (VCC) is generated from the greater voltage on the V1 and V2 inputs. VCC = V1 for options D1 and E1. Note 4: Under typical operating conditions, quiescent current is drawn 140 UNITS 150 5 10 25 100 µs 60 150 300 300 mV mV mV mV from the V1 input. When V2 exceeds V1, V2 supplies the quiescent current. V1 only for options D1 and E1. Note 5: The RST output pin on the LTC2903-1 has an internal pull-up to V2 (for options A1, B1 and C1) of typically 10µA. However, for faster rise times or for VOH voltages greater than V2, use an external pull-up resistor. The internal pull-up is connected to V1 for options D1 and E1. Note 6: For options A1, B1 and C1, the RST pulldown current is derived from V1, V2 and V3. For options D1 and E1, pulldown strength is derived from V1. 29031f a 3 LTC2903-1 U W TYPICAL PERFOR A CE CHARACTERISTICS 5V Threshold Voltage vs Temperature 3.3V Threshold Voltage vs Temperature 2.975 4.475 4.450 4.425 4.400 4.375 4.350 –50 –25 0 25 50 TEMPERATURE (°C) 75 2.250 THRESHOLD VOLTAGE, VRT25 (V) THRESHOLD VOLTAGE, VRT33 (V) 4.500 THRESHOLD VOLTAGE, VRT50 (V) 2.5V Threshold Voltage vs Temperature 2.950 2.925 2.900 2.875 –50 100 0 25 50 TEMPERATURE (°C) –25 75 29031 G01 1.605 1.595 1.585 1.575 75 0.505 0.500 0.495 0 25 50 TEMPERATURE (°C) –25 75 30 25 20 –4.605 –4.630 –4.655 –4.680 –50 10 30 V1 = 5V V2 = 3.3V V3 = 2.5V V4 = 1.8V 25 15 15 10 IV2 10 5 IV2 IV3 5 IV3 0 IV3 –25 V1 = 5V V2 = 3.3V V3 = 1.8V V4 = –5.2V IV1 IV1 IV4 IV4 0 25 50 TEMPERATURE (°C) 75 100 29031 G07 0 –50 100 20 IV2 5 75 Supply Currents vs Temperature (LTC2903-C1) IVX (µA) 15 0 25 50 TEMPERATURE (°C) –25 29031 G06 20 IVX (µA) IVX (µA) –4.580 Supply Currents vs Temperature (LTC2903-B1) V1 = 3.3V V2 = 2.5V V3 = 1.8V 0 –50 100 –4.555 29031 G05 Supply Currents vs Temperature (LTC2903-A1) 100 –4.530 0.490 –50 100 IV1 75 –5.2V Threshold Voltage vs Temperature 29031 G04 25 0 25 50 TEMPERATURE (°C) –25 29031 G03 THRESHOLD VOLTAGE, VRT52N (V) THRESHOLD VOLTAGE, VRTA (V) THRESHOLD VOLTAGE, VRT18 (V) 1.615 30 2.190 2.175 –50 100 0.510 0 25 50 TEMPERATURE (°C) 2.205 ADJ Threshold Voltage vs Temperature 1.625 –25 2.220 29031 G02 1.8V Threshold Voltage vs Temperature 1.565 –50 2.235 –25 0 25 50 TEMPERATURE (°C) 75 100 29031 G08 –5 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 29031 G09 29031f a 4 LTC2903-1 U W TYPICAL PERFOR A CE CHARACTERISTICS 260 TYPICAL TRANSIENT DURATION (µs) LTC2903-E1 20 LTC2903-D1 15 10 5 0 –50 –25 75 0 25 50 TEMPERATURE (°C) 350 300 250 RESET OCCURS ABOVE CURVE 200 150 100 50 0 1 10 100 0.1 RESET COMPARATOR OVERDRIVE (% OF VRTX) 100 RST Output Voltage with 10k Pull-Up to V1 2.5 2.0 1.5 1.0 0 25 50 TEMPERATURE (°C) 0.10 75 100 VIN = V1 = V2 = V3 0.08 0.20 0.15 V1 ONLY 0.10 2.5 3 V1 (V) 3.5 4 4.5 0 5 20µA 0.06 10µA 0.05 0.04 5µA 0.03 0.01 V1 = V2 = V3 2 0.07 0.02 0.05 0.5 1.5 –25 Low Voltage Reset Pull-Down Performance vs External Pull-Up Current and Input Supply Voltage RESET PIN VOLTAGE (V) RST OUTPUT VOLTAGE (V) RST OUTPUT VOLTAGE (V) 3.0 1 160 0.09 3.5 0.5 180 29301 G11 0.25 0 200 140 –50 0.30 4.0 0 220 RST Output Voltage with 10k Pull-Up to V1 V1 = V2 = V3 LTC2903-B1, -C1 4.5 240 29031 G10 29031 G20 5.0 RESET TIME-OUT PERIOD, tRST (ms) 400 25 IV1 (µA) Reset Time-Out Period vs Temperature Transient Duration vs Comparator Overdrive Supply Currents vs Temperature 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 V1 (V) 29031 G12 2µA 1µA 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 VIN, INPUT SUPPLY VOLTAGE (V) 29301 G13 RST Current Sink Capability vs VCC 29031 G14 RST Voltage Output Low vs RST Sink Current 15 1.5 12 1.2 LTC2903-A1, -E1 V1 = 3.3V RST Voltage Output Low vs RST Sink Current 1.5 85°C 1 25°C LTC2903-B1, -C1, -D1 V1 = 5V 25°C 1.2 –45°C 85°C –45°C VOL = 0.2V 6 3 0 0.9 VOL (V) 9 VOL (V) IRST (mA) VOL = 0.4V 0.6 0.6 0.3 0.3 0 0 0.5 1 1.5 2 2.5 3 VCC (V) 3.5 4 4.5 5 29031 G15 0.9 0 0 5 10 15 25 30 IRST (mA) 20 35 40 45 29031 G16 0 10 20 40 30 IRST (mA) 50 60 29031 G16 29031f a 5 LTC2903-1 U W TYPICAL PERFOR A CE CHARACTERISTICS RST Pull-Up Current vs V2 RST Pull-Up Current vs V1 –90 –80 LTC2903-A1, -B1, -C1 –80 V1, V3, V4 ABOVE THRESHOLD LTC2903-D1, -E1 –70 V2, V3, V4 ABOVE THRESHOLD –70 –60 IRST (µA) IRST (µA) –60 –50 –40 LTC2903-D1 –40 –30 –30 –20 –20 VRT25 VRT33 0 0.5 1 1.5 2 2.5 3 V2 (V) 3.5 LTC2903-E1 –10 –10 0 –50 4.5 4 0 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 V1 (V) 29031 G18 29031 G21 RST Pull-Up Current vs External Pull-Down Voltage on RST RST Pull-Up Current vs External Pull-Down Voltage on RST –40 –80 –35 –70 –30 –60 LTC2903-E1 IRST (µA) IRST (µA) LTC2903-B1, -C1 –25 –20 –15 –50 –40 –30 LTC2903-A1 –10 –20 –5 –10 LTC2903-D1 0 0 0 0.5 1 2 1.5 VRST (V) 2.5 3 3.5 0 1 2 3 4 5 6 VRST (V) 29031 G19 29031 G22 29031f a 6 LTC2903-1 U U U PI FU CTIO S V1 (Pin 1): Voltage Input 1. Internal VCC is generated from the greater voltage on the V1 and V2 inputs. VCC = V1 for options D1 and E1. Bypass this pin to ground with a 0.1µF (or greater) capacitor. V3 is an adjustable input for options D1 and E1. See Table 1b for recommended ADJ resistor values. GND (Pin 2): Ground. V4 (Pin 5): Voltage Input 4. Table 1 lists the recommended ADJ resistor values for options A1, B1 and C1. See Table 1b for options D1 and E1. V2 (Pin 3): Voltage Input 2. Internal VCC is generated from the greater voltage on the V1 and V2 inputs. VCC = V1 for options D1 and E1. For option A1, B1, C1 bypass this pin to ground with a 0.1µF (or greater) capacitor. V2 is an adjustable input for options D1 and E1. See Table 1b for recommended ADJ resistor values. RST (Pin 6): Reset Logic Output. Pulls low when any voltage input is below reset threshold and held low for 200ms after all voltage inputs exceed threshold. The pin contains a weak pull-up to V2 (V1 for options D1 and E1). Use an external pull-up for faster rise times or output voltages greater than V2 (V1 for options D1 and E1). V3 (Pin 4): Voltage Input 3. This input assists the RST pulldown circuitry below 1V (for options A1, B1 and C1 only). WU W TI I G DIAGRA VX VRTX tUV RST tRST 1.5V 29031 TD 29031f a 7 LTC2903-1 W BLOCK DIAGRA S V1 1 (LTC2903-A1, LTC2903-B1) – V1 + POWER DETECT V2 VCC V2 10µA V2 3 – RESET DELAY GENERATOR + V3 4 200ms DELAY – V1 V2 V3 + V4 5 6 RST LOW VOLTAGE PULL-DOWN MONITORED VOLTAGES – + BANDGAP REFERENCE GND 2 A1 B1 V1 3.3V 5V V2 2.5V 3.3V V3 1.8V 2.5V V4 ADJ 1.8V 29031 BD1 0.5V (LTC2903-C1) V1 1 – V1 + POWER DETECT V2 VCC V2 10µA V2 3 – RESET DELAY GENERATOR + V3 4 6 RST 200ms DELAY – V1 V2 V3 + LOW VOLTAGE PULL-DOWN MONITORED VOLTAGES V4 5 + – GND 2 BANDGAP REFERENCE V1 5V V2 3.3V V3 1.8V V4 –5.2V 29031 BD3 29031f a 8 LTC2903-1 W BLOCK DIAGRA S (LTC2903-D1, LTC2903-E1) – V1 1 POWER DETECT V1 + VCC V1 10µA – V2 3 RESET DELAY GENERATOR + 6 RST 200ms DELAY – V3 4 V1 + LOW VOLTAGE PULL-DOWN MONITORED VOLTAGES – V4 5 + BANDGAP REFERENCE GND 2 D1 E1 V1 3.3V 5V V2 ADJ ADJ V3 ADJ ADJ V4 ADJ ADJ 29031 BD2 0.5V U W U U APPLICATIO S I FOR ATIO The LTC2903-1 issues a logic low on the RST output when an input supply voltage resides below the prescribed threshold voltage. Ideally, the RST logic output would remain low with the input supply voltage down to zero volts. Most supervisors lack pull-down capability below 1V. The LTC2903-1 power supply supervisors incorporate a new low voltage pull-down circuit that can hold the RST line low with as little as 200mV of input supply voltage on V1, V2 or V3 (V1 only for options D1 and E1). The pull-down circuit helps maintain a low impedance path to ground, reducing the risk of floating the RST node to undetermined voltages. Such voltages may trigger external logic causing erroneous reset operation(s). Furthermore, a mid-scale voltage could cause external circuits to operate in the middle of their voltage transfer characteristic, consuming more quiescent current than normal. These conditions could cause serious system reliability problems. When V1, V2 and V3 are ramped simultaneously (for options A1, B1 and C1 only), the reset pull-down current increases up to three times the current that may be pulled with a single input. Figure 1 demonstrates the reset pin 10000 TA = 25°C VRST = 0.3VCC 1000 IRST (µA) Power-Up V1 = V2 = V3 100 V1 ONLY 10 1 0 0.2 0.4 0.6 VCC (V) 0.8 1.0 1.2 29031 F01 Figure 1. RST Pull-Down Current vs VCC 29031f a 9 LTC2903-1 U W U U APPLICATIO S I FOR ATIO current sinking ability for single supply and triple supplytracking applications. Figure 2 shows a detailed view of the reset pin voltage with a 10k pull-up resistor to V1. The LTC2903-1 supervisors derive their internal supply voltage (VCC) automatically from the greater voltage on the V1 and V2 inputs (VCC = V1 for options D1 and E1). With all supply inputs above threshold, the quiescent current drawn from VCC is 20µA (typ). Supply Monitoring The LTC2903-1 accurately monitors four inputs in a small 6-lead SOT-23 package. The low voltage reset output includes an integrated 200ms reset delay timer. The reset line pulls high 200ms after all voltage inputs exceed their respective thresholds. The reset output remains low during power-up, power-down and brownout conditions on any of the voltage inputs. Triple Adjustable Options (LTC2903-D1, LTC2903-E1) LTC2903-D1 and LTC2903-E1 provide 3 adjustable inputs: V2, V3 and V4. The V1 threshold is 3.086V (3.3V, 5%) for option D1 and 4.675 (5V, 5%) for option E1. For each supply monitored by an adjustable input, connect an external resistor divider (R1 and R2) between the positive voltage being sensed and ground. The tap point for each divider is then connected to each adjustable input. All adjustable inputs are compared to an internal 0.5V reference. Figure 3 shows how each adjustable input is configured. Calculate the trip voltage from: ⎛ R1⎞ VTRIP = 0.5V⎜ 1 + ⎟ ⎝ R2 ⎠ VTRIP LTC2903-A1 0.7 R1 TA = 25°C RST OUTPUT VOLTAGE (V) – V4 0.6 R2 0.5 0.4 + COMPETITION PART 0.5V + – 0.3 29031 F03 0.2 0.1 V1 ONLY V1 = V2 = V3 Figure 3. Setting the Positive Adjustable Trip Point 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 V1 (V) 29031 F02 Figure 2. RST Output Voltage with a 10k Pull-Up to V1 (Enlarged Area of Detail) 29031f a 10 LTC2903-1 U W U U APPLICATIO S I FOR ATIO Table 1a. Suggested 1% Resistor Values for the –11.5% ADJ Inputs VSUPPLY (V) VTRIP (V) R1 (kΩ) R2(kΩ) 12 10.75 2050 100 10 8.95 1690 100 8 7.15 1330 100 7.5 6.7 1240 100 6 5.38 976 100 5 4.435 787 100 3.3 2.935 487 100 3 2.66 432 100 2.5 2.2 340 100 1.8 1.605 221 100 1.5 1.325 165 100 1.2 1.065 113 100 1 0.884 76.8 100 0.9 0.795 59 100 Table 1b contains suggested 1% resistor values for the ADJ inputs to obtain nominal –6.5% thresholds. Table 1b. Suggested 1% Resistor Values for the –6.5% ADJ Inputs VSUPPLY (V) VTRIP (V) R1 (kΩ) R2(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 0.933 86.6 100 0.9 0.840 68.1 100 0.8 0.750 49.9 100 0.7 0.655 30.9 100 0.6 0.561 12.1 100 Implications of Threshold Accuracy Specifying system voltage margin for worst-case operation requires consideration of three factors: power supply tolerance, IC supply voltage tolerance and supervisor reset threshold accuracy. Highly accurate supervisors ease the design challenge by decreasing the overall voltage margin required for reliable system operation. Consider a 5V system with a ±10% power supply tolerance band. System ICs powered by this supply must operate reliably within this band (and a little more, as explained below). The bottom of the supply tolerance band, at 4.5V (5V – 10%), is the exact voltage at which a perfectly accurate supervisor generates a reset. Such a perfectly accurate supervisor does not exist—the actual reset threshold may vary over a specified band (±1.5% for the LTC2903-1 supervisors). Figure 4 shows the typical relative threshold accuracy for all four inputs, over temperature. With this variation of reset threshold in mind, the nominal reset threshold of the supervisor resides below the minimum supply voltage, just enough so that the reset threshold band and the power supply tolerance bands do not overlap. If the two bands overlap, the supervisor could generate a false or nuisance reset when the power supply remains within its specified tolerance band (say, at 4.6V). Adding half of the reset threshold accuracy spread (1.5%) to the ideal 10% thresholds puts the LTC2903-1 thresholds at 11.5% (typ) below the nominal input voltage. For example, the 5V typical threshold is 4.425V, or 75mV below the ideal threshold of 4.500V. The guaranteed threshold lies in the band between 4.500V and 4.350V over temperature. 1.5 TYPICAL THRESHOLD ACCURACY (%) Table 1a contains suggested 1% resistor values for the ADJ inputs to obtain nominal –11.5% thresholds. Connect unused supervisor inputs to the highest supply voltage available. 1.0 0.5 0 –0.5 –1.0 –1.5 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 29031 F04 Figure 4. LTC2903 Typical Threshold Accuracy vs Temperature 29031f a 11 LTC2903-1 U W U U APPLICATIO S I FOR ATIO The powered system must work reliably down to the lowest voltage in the threshold band or risk malfunction before the reset line falls. In the 5V example, using the 1.5% accurate supervisor, the system ICs must work down to 4.35V. System ICs working with a ±2.5% accurate supervisor must operate down to 4.25V, increasing the required system voltage margin and the probability of system malfunction. In any supervisory application, supply noise riding on the monitored DC voltage can cause spurious resets, particularly when the monitored voltage approaches the reset threshold. A less than desirable but commonly used technique used to mitigate this problem adds hysteresis to the input comparator. The amount of added hysteresis, usually specified as a percentage of the trip threshold, effectively degrades the advertised accuracy of the part. To maintain high accuracy, the LTC2903-1 does not use hysteresis. To minimize spurious resets while maintaining threshold accuracy, the LTC2903-1 employs two forms of noise filtering. The first line of defense incorporates proprietary tailoring of the comparator transient response. Transient events receive electronic integration in the comparator and must exceed a certain magnitude and duration to cause the comparator to switch. Figure 5 illustrates the typical transient duration versus comparator overdrive (as a percentage of the trip threshold VRT) required to trip the comparators. Once any comparator is switched, the reset line pulls low. The reset time-out counter starts once TYPICAL TRANSIENT DURATION (µs) 400 TA = 25°C 350 300 250 200 RESET OCCURS ABOVE CURVE all inputs return above threshold. The nominal reset delay time is 200ms. The counter clears whenever any input drops back below threshold. This reset delay time effectively provides further filtering of the voltage inputs. A noisy input with frequency components of sufficient magnitude above f = 1/tRST = 5Hz holds the reset line low, preventing oscillatory behavior on the reset line. Although all four comparators have built-in glitch filtering, use bypass capacitors on the V1 and V2 inputs because the greater of V1 or V2 supplies the VCC (options A1, B1 and C1) for the part (a 0.1µF ceramic capacitor satisfies most applications). Apply filter capacitors on the V3 and V4 inputs in extremely noisy situations. Options D1 and E1 require a bypass capacitor only on V1. Apply filter capacitors on V2, V3 and V4 adjustable inputs in extremely noisy situations. Reset Output Rise and Fall Time Estimation The reset output line contains a weak pull-up current source to the V2 supply (V1 for options D1 and E1). Use an external pull-up resistor when the output needs to pull to another voltage and/or when the reset output needs a faster rise time. The open-drain output allows for wiredOR connections when more than one signal needs to pull down on the reset line. Estimate output rise time for the open-drain output without an external pull-up using: tRISE ≈ 2.2 • RPU • CLOAD where RPU is the on-resistance of the pull-up transistor and CLOAD is the external load capacitance on the pin. At room temperature, the average RPU is approximately 50kΩ. When externally pulling up to voltages higher than V2 (V1 for options D1 and E1), an internal network automatically protects the weak pull-up circuitry from reverse currents. The reset output has very strong pull-down capability. Estimate the output fall time using: 150 100 tFALL ≈ 2.2 • RPD • CLOAD 50 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE (% OF VRTX) 29031 F05 Figure 5. Typical Transient Duration vs Overdrive Required to Trip Comparator where RPD is the on-resistance of the pull-down transistor and CLOAD is the external load capacitance on the pin. At room temperature, the average RPD is approximately 40Ω. With a 150pF load capacitance the reset line can pull down in about 13ns. 29031f a 12 LTC2903-1 U TYPICAL APPLICATIO S Quad Supply Monitor with Adjustable Input 1 3.3V C1 0.1µF V1 RST 6 SYSTEM RESET LTC2903-A1 2 GND V4 R1 76.8k 5 R2 100k C2 0.1µF 3 2.5V V2 V3 4 1V (VTRIP = 0.884V) 1.8V 2903 TA02 Fixed Quad Supply Monitor with LED Indication on RST 5V 1k LED 1 5V C1 0.1µF V1 RST 6 SYSTEM RESET LTC2903-B1 2 GND V4 V2 V3 5 1.8V C2 0.1µF 3.3V 3 4 2.5V 2903 TA05 29031f a 13 LTC2903-1 U TYPICAL APPLICATIO S Quad Supply Monitor with Unused Input Pulled Above Threshold 1 5V C1 0.1µF V1 RST 6 SYSTEM RESET LTC2903-C1 2 GND V4 V2 V3 5 –5.2V C2 0.1µF 3 3.3V 4 2903 TA03 Quad Supply Monitor with 3 Adjustable Inputs Monitoring 5% Supplies 1 3.3V C1 0.1µF V1 RST 6 SYSTEM RESET LTC2903-D1 2 GND V4 2150k 5 12V (VTRIP = 11.25V) 100k 237k 1.8V (VTRIP = 1.685V) 3 100k V2 V3 2903 TA06 365k 4 100k 2.5V (VTRIP = 2.325V) 29031f a 14 LTC2903-1 U PACKAGE DESCRIPTIO S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 3.85 MAX 2.62 REF 1.4 MIN 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.90 BSC S6 TSOT-23 0302 NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 29031f a 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 LTC2903-1 U TYPICAL APPLICATIO Quad Supply Monitor with Manual Reset Button 3.3V R3 10k 3.3V V1 C1 0.1µF RST LTC2903-A1 GND SYSTEM RESET 12V (VTRIP = 10.75V) V4 R2 100k C2 0.1µF V2 2.5V MANUAL RESET BUTTON R1 RESD* (NORMALLY OPEN) 2050k 10k 1.8V V3 2903 TA04 *OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65 Threshold LTC694-3.3 3.3V Supply Monitor, Watchdog Timer and Battery Backup 2.9V Threshold LTC699 5V Supply Monitor and Watchdog Timer 4.65 Threshold LTC1232 5V Supply Monitor, Watchdog Timer and Pushbutton 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 Monitors with Open-Drain Reset Individual Monitor Outputs in MSOP LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitors with Open-Drain Reset 5-Lead SOT-23 Package LTC1728-2.5/LTC1728-5 Micropower Triple Supply Monitors 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 Quad Voltage Monitor in MSOP 16 User Selectable Combinations, ±1.5% Threshold Accuracy LTC2901 Quad Voltage Monitor with Watchdog 16 User Selectable Combinations, Adjustable Timers LTC2902 Quad Voltage Monitor with RST Disable 16 User Selectable Combinations, Adjustable Tolerance LTC2904/LTC2905/ LTC2906/LTC2907 Precision Dual Supply Monitors Pin Selectable Thresholds LTC2908 Precision Six Supply Monitor 8-Lead SOT-23 and DFN Packages LTC2920-1/LTC2920-2 Single/Dual Power Supply Margining Controller