LTC2908 Precision Six Input Supply Monitor FEATURES DESCRIPTION n The LTC®2908 is a six input supply monitor for systems requiring a precise and compact monitoring solution for multiple supply voltages. The inputs can be shorted together for monitoring systems with fewer than six supply voltages, and the open drain RST output of two or more LTC2908 can be wired-OR together for monitoring systems with more than six supply voltages. The common reset output remains low until all six inputs have been in compliance for 200ms. n n n n n n n Ultralow Voltage Reset: VCC = 0.5V Guaranteed* Monitors Six Inputs Simultaneously: 5V, 3.3V, 2.5V, 1.8V, ADJ1, ADJ2 (LTC2908-A1) 3.3V, 2.5V, 1.8V, 1.5V, ADJ1, ADJ2 (LTC2908-B1) 2.5V, ADJ1, ADJ2, ADJ3, ADJ4, ADJ5 (LTC2908-C1) Guaranteed Threshold Accuracy: ±1.5% of Monitored Voltage Over Temperature Internal VCC Auto Select Power Supply Glitch Immunity 200ms Reset Time Delay Active Low Open-Drain RST Output Low Profile (1mm) 8-Lead SOT-23 (ThinSOT™) and Plastic (3mm × 2mm) DFN Packages The LTC2908 features a tight 1.5% threshold accuracy over the entire operating temperature range and glitch immunity to ensure reliable reset operation without false triggering. The open-drain RST output state is guaranteed to be in the correct state as long as V1 and/or V2 is 0.5V or greater. APPLICATIONS n n n n n The LTC2908 also features adjustable inputs with a nominal threshold level at 0.5V. This product provides a precise, space-conscious, micropower and general purpose solution for any kind of system requiring supply monitors. Network Servers Wireless Base Stations Optical Networking Systems Multivoltage Systems Desktop and Notebook Computers , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Patent pending. TYPICAL APPLICATION Six Supply Monitor with 5% Tolerance (12V, 3.3V, 2.5V, 1.8V, 1.5V, 1.2V) RST Output Voltage vs V1 with 10k Pull-Up Resistor to V1 12V DC/DC DC/DC DC/DC DC/DC 3.3V 0.4 V3 = V4 = VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = GND 2.5V SYSTEM 1.8V 1.5V 1.2V 0.1μF 0.1μF 2.15M 100k 124k 100k RST OUTPUT VOLTAGE (V) DC/DC 0.3 V1 INPUT 0.2 V2 = GND 0.1 V2 = V1 (A1/B1) V1 V2 V3 V4 VADJ1 LTC2908-B1 GND 0 VADJ2 RST 0 0.2 0.4 0.6 0.8 V1 (V) 2908 TA01a 2908 TA01b 2908fc 1 LTC2908 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2) Terminal Voltages V1, V2, V3, V4 .........................................– 0.3V to 7V VADJ1, VADJ2, VADJ3, ..................–0.3V to (VCC + 0.6V) VADJ4, VADJ5 .............................–0.3V to (VCC + 0.6V) RST.......................................................... –0.3V to 7V Operating Temperature Range LTC2908C ................................................ 0°C to 70°C LTC2908I..............................................–40°C to 85°C Storage Temperature Range DFN Package......................................–65°C to 125°C TSOT-23 Package...............................–65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C PIN CONFIGURATION LTC2908CDDB-A1 LTC2908IDDB-A1 LTC2908CDDB-B1 LTC2908IDDB-B1 LTC2908CDDB-C1 LTC2908IDDB-C1 TOP VIEW LTC2908CTS8-A1 LTC2908ITS8-A1 LTC2908CTS8-B1 LTC2908ITS8-B1 TOP VIEW GND 1 8 VADJ2 GND 1 8 VADJ4 RST 2 7 V3 RST 2 7 VADJ3 V2 1 6 VADJ2 V4 2 RST 3 GND 4 V4 3 9 V2 4 LTC2908CTS8-C1 LTC2908ITS8-C1 6 VADJ1 5 V1 DDB8 PACKAGE 8-LEAD (3mm × 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 76°C/W EXPOSED PAD (PIN 9) (PCB CONNECTION OPTIONAL) VADJ5 3 V1 4 9 5 VADJ1 DDB8 PACKAGE 8-LEAD (3mm × 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 76°C/W EXPOSED PAD (PIN 9) (PCB CONNECTION OPTIONAL) TOP VIEW TOP VIEW 8 V1 7 VADJ1 6 V3 5 VADJ2 TS8 PACKAGE 8-LEAD PLASTIC TSOT-23 TJMAX = 125°C, θJA = 250°C/W V1 1 VADJ5 2 RST 3 GND 4 8 VADJ1 7 VADJ2 6 VADJ3 5 VADJ4 TS8 PACKAGE 8-LEAD PLASTIC TSOT-23 TJMAX = 125°C, θJA = 250°C/W ORDER INFORMATION Lead Free Finish TAPE AND REEL (MINI) TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION LTC2908CDDB-A1#TRMPBF LTC2908CDDB-A1#TRMPBF LBFD 8-LEAD (3mm × 2mm) PLASTIC DFN LTC2908IDDB-A1#TRMPBF LTC2908IDDB-A1#TRMPBF LBFF 8-LEAD (3mm × 2mm) PLASTIC DFN LTC2908CDDB-B1#TRMPBF LTC2908CDDB-B1#TRMPBF LBFG 8-LEAD (3mm × 2mm) PLASTIC DFN LTC2908IDDB-B1#TRMPBF LTC2908IDDB-B1#TRMPBF LBFH 8-LEAD (3mm × 2mm) PLASTIC DFN LTC2908CDDB-C1#TRMPBF LTC2908CDDB-C1#TRMPBF LCFV 8-LEAD (3mm × 2mm) PLASTIC DFN LTC2908IDDB-C1#TRMPBF LTC2908IDDB-C1#TRMPBF LCFV 8-LEAD (3mm × 2mm) PLASTIC DFN LTC2908CTS8-A1#TRMPBF LTC2908CTS8-A1#TRMPBF LTBFJ 8-LEAD PLASTIC TSOT-23 LTC2908ITS8-A1#TRMPBF LTC2908ITS8-A1#TRMPBF LTBFK 8-LEAD PLASTIC TSOT-23 LTC2908CTS8-B1#TRMPBF LTC2908CTS8-B1#TRMPBF LTBFM 8-LEAD PLASTIC TSOT-23 LTC2908ITS8-B1#TRMPBF LTC2908ITS8-B1#TRMPBF LTBFN 8-LEAD PLASTIC TSOT-23 LTC2908CTS8-C1#TRMPBF LTC2908CTS8-C1#TRMPBF LTCFT 8-LEAD PLASTIC TSOT-23 LTC2908ITS8-C1#TRMPBF LTC2908ITS8-C1#TRMPBF LTCFT 8-LEAD PLASTIC TSOT-23 TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ TEMPERATURE RANGE 0°C to 70°C –40°C to 85°C 0°C to 70°C –40°C to 85°C 0°C to 70°C –40°C to 85°C 0°C to 70°C –40°C to 85°C 0°C to 70°C –40°C to 85°C 0°C to 70°C –40°C to 85°C 2908fc 2 LTC2908 ELECTRICAL CHARACTERISTICS (LTC2908-A1) The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VCC = 5V unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT50 5V, 5% Reset Threshold V1 Input Threshold l 4.600 4.675 4.750 V VRT33 3.3V, 5% Reset Threshold V2 Input Threshold l 3.036 3.086 3.135 V VRT25 2.5V, 5% Reset Threshold V3 Input Threshold l 2.300 2.338 2.375 V VRT18 1.8V, 5% Reset Threshold V4 Input Threshold l 1.656 1.683 1.710 V VRTADJ ADJ, 5% Reset Threshold VADJ1, VADJ2 Input Threshold l 0.492 0.500 0.508 V (LTC2908-B1) The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VCC = 3.3V unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT33 3.3V, 5% Reset Threshold V1 Input Threshold l 3.036 3.086 3.135 V VRT25 2.5V, 5% Reset Threshold V2 Input Threshold l 2.300 2.338 2.375 V VRT18 1.8V, 5% Reset Threshold V3 Input Threshold l 1.656 1.683 1.720 V VRT15 1.5V, 5% Reset Threshold V4 Input Threshold l 1.380 1.403 1.425 V VRTADJ ADJ, 5% Reset Threshold VADJ1, VADJ2 Input Threshold l 0.492 0.500 0.508 V (LTC2908-C1) The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VCC = 2.5V unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VRT25 2.5V, 5% Reset Threshold V1 Input Threshold l 2.300 2.338 2.375 V VRTADJ ADJ, 5% Reset Threshold VADJ1, VADJ2, VADJ3, VADJ4, VADJ5, Input Threshold l 0.492 0.500 0.508 V The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VCC = 5V for the LT2908-A1, VCC = 3.3V for the LTC2908-B1or VCC = 2.5V for the LTC2908-C1, unless otherwise noted. (Notes 2, 3) SYMBOL PARAMETER CONDITIONS VCC Internal Supply Voltage RST in Correct Logic State l MIN IV1 V1 Input Current (Note 4) V1 = 5.0V (LTC2908-A1) V1 = 3.3V (LTC2908-B1) V1 = 2.5V (LTC2908-C1) l l l IV2 V2 Input Current (Note 4) V2 = 3.3V (LTC2908-A1) V2 = 2.5V (LTC2908-B1) IV3 V3 Input Current IV4 IVADJ TYP 0.5 MAX UNITS 6 V 26 24 22 70 70 70 μA μA μA l l 10 8 30 30 μA μA V3 = 2.5V (LTC2908-A1) V3 = 1.8V (LTC2908-B1) l l 2 2 5 5 μA μA V4 Input Current V4 = 1.8V (LTC2908-A1) V4 = 1.5V (LTC2908-B1) l l 2 2 5 5 μA μA VADJ1, VADJ2, VADJ3, VADJ4, VADJ5 Input Current VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = 0.55V l ±15 nA 2908fc 3 LTC2908 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VCC = 5V for the LT2908-A1, VCC = 3.3V for the LTC2908-B1 or VCC = 2.5V for the LTC2908-C1, unless otherwise noted. (Notes 2, 3) SYMBOL PARAMETER CONDITIONS tRST Reset Time-Out Period tUV VX Undervoltage Detect to RST VX Less Than Reset Threshold VRTX by More Than 1% VOH Output Voltage High RST (Note 5) IRST = –1μA, VCC = 5V (LTC2908-A1) IRST = –1μA, VCC = 3.3V (LTC2908-B1) IRST = –1μA, VCC = 2.5V (LTC2908-C1) l l l VOL Output Voltage Low RST VCC = 0.5V, IRST = 5μA VCC = 1.0V, IRST = 100μA VCC = 3.0V, IRST = 2500μA l l l l Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliabilty and lifetime. Note 2: The greater of V1, V2 is the internal supply voltage (VCC) for the LTC2908-A1 and the LTC2908-B1. V1 is the internal supply voltage (VCC) for the LTC2908-C1. MIN TYP MAX UNITS 160 200 260 ms 250 μs VCC – 1.5 VCC – 1.0 VCC – 1.0 V V V 0.01 0.01 0.10 0.15 0.15 0.30 V V V Note 3: All currents into pins are positive; all voltages are referenced to GND unless otherwise noted. Note 4: Under typical operating conditions, most of the quiescent current is drawn from the V1 input. When V2 exceeds V1, V2 supplies most of the quiescent current. Note 5: The output pin RST has an internal pull-up to VCC of typically 6μA. However, an external pull-up resistor may be used when a faster rise time is required or for VOH voltages greater than VCC. TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at TA = 25°C unless otherwise noted. 5V Threshold Voltage vs Temperature 3.3V Threshold Voltage vs Temperature 3.135 2.375 4.725 THRESHOLD VOLTAGE, VRT25 (V) THRESHOLD VOLTAGE, VRT50 (V) THRESHOLD VOLTAGE, VRT33 (V) 4.750 3.115 4.700 2.360 3.095 4.675 2.345 3.075 4.650 2.330 3.055 4.625 4.600 –50 2.5V Threshold Voltage vs Temperature –25 50 25 0 TEMPERATURE (°C) 75 100 2908 G01 3.035 –50 2.315 –25 50 25 0 TEMPERATURE (°C) 75 100 2908 G02 2.300 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 2908 G03 2908fc 4 LTC2908 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at TA = 25°C unless otherwise noted. 1.8V Threshold Voltage vs Temperature 1.5V Threshold Voltage vs Temperature 1.700 1.690 1.680 1.670 1.425 0.5080 1.420 0.5060 THRESHOLD VOLTAGE, VRTADJ (V) THRESHOLD VOLTAGE, VRT15 (V) THRESHOLD VOLTAGE, VRT18 (V) 1.710 ADJ Threshold Voltage vs Temperature 1.415 1.410 1.405 1.400 1.395 1.390 1.385 –25 50 25 0 TEMPERATURE (°C) 75 100 1.380 –50 –25 0 25 50 TEMPERATURE (°C) 75 2908 G04 0.5000 0.4980 0.4960 0.4940 0.4920 –50 IV1 vs Temperature V1 = 5.0V (A1)/V1 = 3.3V (B1) 2.1 V2 = 3.3V (A1)/V2 = 2.5V (B1) V3 = 2.5V (A1)/V3 = 1.8V (B1) 2.0 V4 = 1.8V (A1)/V4 = 1.5V (B1) VADJ1 = VADJ2 = 0.55V 1.9 10 A1 9 B1 8 23 C1 1.8 1.7 7 21 100 2.2 V1 = 5.0V (A1)/V1 = 3.3V (B1) 13 V2 = 3.3V (A1)/V2 = 2.5V (B1) V3 = 2.5V (A1)/V3 = 1.8V (B1) 12 V4 = 1.8V (A1)/V4 = 1.5V (B1) 11 VADJ1 = VADJ2 = 0.55V IV2 (μA) 25 75 IV3 vs Temperature 14 V1 = 5.0V (A1)/V1 = 3.3V (B1)/V1 = 2.5V (C1) 31 V2 = 3.3V (A1)/V2 = 2.5V (B1) V3 = 2.5V (A1)/V3 = 1.8V (B1) 29 V4 = 1.8V (A1)/V1 = 1.5V (B1) VADJ1 = VADJ2 = VADJ3 = 27 VADJ4 =VADJ5 = 0.55V B1 0 50 25 TEMPERATURE (°C) 2908 G06 IV2 vs Temperature A1 –25 2908 G05 33 IV1 (μA) 100 0.5020 IV3 (μA) 1.660 –50 0.5040 1.6 6 19 1.5 5 –25 0 25 50 TEMPERATURE (°C) 75 4 –50 100 –25 0 50 25 TEMPERATURE (°C) 75 2908 G07 700 2.2 TYPICAL TRANSIENT DURATION (μs) IV4 (μA) 1.9 1.8 1.7 1.6 1.5 –25 0 50 25 TEMPERATURE (°C) 75 100 2908 G10 0 50 25 TEMPERATURE (°C) 75 Reset Time-Out Period (tRST) vs Temperature 250 TA = 25°C 600 500 100 2908 G09 Typical Transient Duration vs Comparator Overdrive V1 = 5.0V (A1)/V1 = 3.3V (B1) 2.1 V2 = 3.3V (A1)/V2 = 2.5V (B1) V3 = 2.5V (A1)/V3 = 1.8V (B1) 2.0 V4 = 1.8V (A1)/V4 = 1.5V (B1) VADJ1 = VADJ2 = 0.55V –25 2908 G08 IV4 vs Temperature 1.4 –50 1.4 –50 100 RESET TIME-OUT PERIOD, tRST (ms) 17 –50 RESET OCCURS ABOVE CURVE 400 300 200 100 0 0.1 1 10 100 COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 2908 G11 240 230 220 210 200 190 180 170 160 150 –50 –25 0 50 25 TEMPERATURE (°C) 75 100 2908 G12 2908fc 5 LTC2908 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at TA = 25°C unless otherwise noted. 0.4 V1 = V2 (A1/B1) V3 = 2.5V (A1)/V3 = 1.8V (B1) V4 = 1.8V (A1)/V4 = 1.5V (B1) 4.0 V ADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = 0.55V RST OUTPUT VOLTAGE (V) 3.0 VRT33 LTC2908-B1 2.0 0.3 V1 = INPUT 0.2 V2 = GND 0.1 1.0 V2 = V1 VRT50 LTC2908-A1 0 1 0 3 2 4 5 0 0.4 0.2 RST Pull-Down Current vs Supply Voltage LTC2908-C1 10 RST AT 150mV 3.0 2.5 2.0 1.5 RST AT 50mV 0 VRT25 LTC2908-C1 0.5 2.0 1.5 SUPPLY VOLTAGE VCC (V) 0 1.0 1 RST AT 150mV 0.1 RST AT 50mV 2.5 25°C 0.3 0.2 0.1 0 RST AT 50mV 0 2908 G17 1.20 V1 = 3.3V 0.7 V2 = 2.5V V3 = 1.8V 0.6 V4 = 1.5V VADJ1 = VADJ2 = 0.4V 2908 G18 1.0 V1 = 2.5V VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = 0.4V 85°C 25°C 0.80 0.5 85°C 1 0.2 0.4 0.6 0.8 SUPPLY VOLTAGE, VCC (V) RST Output Voltage Low vs RST Pull-Down Current LTC2908-C1 –40°C 0.4 –40°C 0.60 25°C 0.3 0.40 0.2 0.20 0.1 0 25 30 35 20 15 RST PULL-DOWN CURRENT, IRST (mA) 10 RST AT 150mV 0.1 2908 G16 RST OUTPUT VOLTAGE LOW, VOL (V) RST OUTPUT VOLTAGE LOW, VOL (V) –40°C 0.4 VCC = V1 V2 = V3 = V4 = VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = GND 1 1 0.2 0.4 0.6 0.8 SUPPLY VOLTAGE, VCC (V) 0.8 0.5 5 2908 G15 RST Output Voltage Low vs RST Pull-Down Current LTC2908-B1 V1 = 5.0V 0.7 V2 = 3.3V V3 = 2.5V 0.6 V4 = 1.8V VADJ1 = VADJ2 = 0.4V 2 3 4 SUPPLY VOLTAGE, VCC (V) 0.001 0 0.8 5 1 0 RST AT 50mV VRT50 LTC2908-A1 0.01 0.001 RST Output Voltage Low vs RST Pull-Down Current LTC2908-A1 0 VRT33 LTC2908-B1 10 VCC = V1 = V2 V3 = V4 = VADJ1 = VADJ2 = GND 2928 G25 85°C 1 RST Pull-Down Current vs Supply Voltage with 1 Input 0.01 1.0 0.5 2 RST Pull-Down Current vs Supply Voltage with 2 Inputs LTC2908-A1/LTC29089-B1 RST PULL-DOWN CURRENT, IRST (mA) RST PULL-DOWN CURRENT, IRST (mA) 3.5 3 2908 G14 2908 G13 VCC = V1 VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = 0.55V RST AT 150mV 4 V1 (V) V1 (V) 4.0 0.8 0.6 VCC = V1 = V2 V3 = 2.5V (A1)/V3 = 1.8V (B1) 5 V4 = 1.8V (A1)/V4 = 1.5V (B1) VADJ1 = VADJ2 = 0.55V 0 RST PULL-DOWN CURRENT, IRST (mA) 0 6 V3 = V4 = VADJ1 = VADJ2 = GND (A1/B1) VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = GND (C1) RST OUTPUT VOLTAGE LOW, VOL (V) RST OUTPUT VOLTAGE (V) 5.0 VRT25 LTC2908-C1 RST Pull-Down Current vs Supply Voltage LTC2908-A1/LTC2908-B1 RST Output Voltage vs V1 with 10k Pull-Up Resistor to V1 RST PULL-DOWN CURRENT, IRST (mA) RST Output Voltage vs V1 with 10k Pull-Up Resistor to V1 0 5 10 20 15 RST PULL-DOWN CURRENT, IRST (mA) 25 2908 G19 0.00 0.0 25.0 5.0 10.0 15.0 20.0 RST PULL-DOWN CURRENT, IRST (mA) 2908 G23 2908fc 6 LTC2908 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are at TA = 25°C unless otherwise noted. RST Output Voltage High vs RST Output Source Current LTC2908-A1 RST Pull-Up Current vs Supply Voltage –25 –20 5 VCC = V1 = V2 (A1/B1), VCC = V1(C1) V3 = 2.5V (A1)/V3 = 1.8V (B1) V4 = 1.8V (A1)/V4 = 1.5V (B1) VADJ1 = VADJ2 = 0.55V (A1/B1) VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = 0.55V(C1) RST HELD AT 0V –15 RST OUTPUT VOLTAGE HIGH, VOH (V) RST PULL-UP CURRENT, IRST (μA) –30 VRT25 LTC2908-C1 VRT33 LTC2908-B1 –10 –5 0 1.5 VRT50 LTC2908-A1 2 3.5 4.5 3 4 2.5 SUPPLY VOLTAGE, VCC (V) 4 3 25°C –40°C 1 5 V1 = 5.0V V2 = 3.3V V3 = 2.5V V4 = 1.8V VADJ1 = VADJ2 = 0.55V 2 0 2908 G20 –4 –12 –16 –20 –8 OUTPUT SOURCE CURRENT, IRST (μA) 2908 G21 RST Output Voltage High vs RST Output Source Current LTC2908-B1 RST Output Voltage High vs RST Output Source Current LTC2908-C1 2.0 2.5 2.0 25°C 1.5 85°C –40°C V1 = 3.3V V2 = 2.5V 1.0 V3 = 1.8V V4 = 1.5V VADJ1 = VADJ2 = 0.55V 0.5 –4 –6 –8 –10 –12 0 –2 OUTPUT SOURCE CURRENT, IRST (μA) RST OUTPUT VOLTAGE HIGH VOH (V) 3.0 RST OUTPUT VOLTAGE HIGH, VOH (V) 85°C 1.5 85°C 1.0 0.5 –40°C V1 = 2.5V VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = 0.55V 0 25°C –1 –2 –3 –4 –5 –6 –7 OUTPUT SOURCE CURRENT, IRST (μA) –8 2908 G22 2908 G24 PIN FUNCTIONS (TS8 Package/DDB8 Package) LTC2908-A1/LTC2908-B1 V2 (Pin 1/Pin 4): Voltage Input 2. The greater of V1, V2 is also the internal VCC. The operating voltage on this pin shall not exceed 6V. When in normal operation (V1 > V2), this pin draws approximately 8μA. When this pin is acting as the VCC (V2 > V1), this pin draws an additional 16μA. Bypass this pin to ground with a 0.1μF (or greater) capacitor. V4 (Pin 2/Pin 3): Voltage Input 4. RST (Pin 3/Pin 2): Reset Logic Output. Pulls low when any voltage input is below the reset threshold and is held low for 200ms after all voltage inputs are above threshold. This pin has a weak pull-up to VCC and may be pulled above VCC using an external pull-up. GND (Pin 4/Pin 1): Device Ground. VADJ2 (Pin 5/Pin 8): Adjustable Voltage Input 2. See Table 1 for recommended ADJ resistors values. V3 (Pin 6/Pin 7): Voltage Input 3. VADJ1 (Pin 7/Pin 6): Adjustable Voltage Input 1. See Table 1 for recommended ADJ resistors values. V1 (Pin 8/Pin 5): Voltage Input 1. The greater of V1, V2 is also the internal VCC. The operating voltage on this pin shall not exceed 6V. When in normal operation (V1 > V2), this pin draws approximately 26 μA. When this pin is not acting as the VCC (V2 > V1), this pin draws approximately 8μA. Bypass this pin to ground with a 0.1μF (or greater) capacitor. Exposed Pad (Pin 9, DDB8 Only): Exposed Pad may be left open or connected to device ground. 2908fc 7 LTC2908 PIN FUNCTIONS (TS8 Package/DDB8 Package) LTC2908-C1 V1 (Pin 1/Pin 4): Voltage Input 1. V1 is the internal VCC. The operating voltage on this pin shall not exceed 6V. When in normal operation, this pin draws approximately 22μA. Bypass this pin to ground with a 0.1μF (or greater) capacitor. VADJ5 (Pin 2/Pin 3): Adjustable Voltage Input 5. See Table 1 for recommended ADJ resistors values. RST (Pin 3/Pin 4): Reset Logic Output. Pulls low when any voltage input is below the reset threshold and is held low for 200ms after all voltage inputs are above threshold. This pin has a weak pull-up to Vcc and may be pulled above Vcc using an external pull-up. GND (Pin 4/Pin 1): Device Ground. VADJ4 (Pin 5/Pin 8): Adjustable Voltage Input 4. See Table 1 for recommended ADJ resistors values. VADJ3 (Pin 6/Pin 7): Adjustable Voltage Input 3. See Table 1 for recommended ADJ resistors values. VADJ2 (Pin 7/Pin 6): Adjustable Voltage Input 2. See Table 1 for recommended ADJ resistors values. VADJ1 (Pin 8/Pin 5): Adjustable Voltage Input 1. See Table 1 for recommended ADJ resistors values. Exposed Pad (Pin 9, DDB8 Only): Exposed Pad may be left open or connected to device ground. BLOCK DIAGRAMS LTC2908-A1/LTC2908-B1 – V1 POWER DETECT V2 + C1 VCC – + C2 VCC V3 – + V4 C4 C5 – + GND RST 200ms RESET PULSE GENERATOR – + VADJ2 C3 – + VADJ1 6μA C6 BANDGAP REFERENCE 2908 BD 2908fc 8 LTC2908 BLOCK DIAGRAMS LTC2908-C1 – V1 + C1 – VADJ1 + C2 V1 – VADJ2 + 6μA C3 RST 200ms RESET PULSE GENERATOR – VADJ3 + C4 – VADJ4 + C5 – VADJ5 + GND C6 BANDGAP REFERENCE 2908 BDa TIMING DIAGRAM VX Monitor Timing VX VRTX tUV RST tRST 1V 2908 TD 2908fc 9 LTC2908 APPLICATIONS INFORMATION Supply Monitoring The LTC2908 is a low power, high accuracy, six input supply monitoring circuit with two adjustable inputs. The reset delay is set to a nominal of 200ms with an internal capacitor, eliminating the need for an external timing capacitor. All input voltages must be above predetermined thresholds for the reset not to be invoked. The LTC2908 asserts the reset output during power-up, power-down and brownout conditions on any one of the voltage inputs. Ultralow Voltage Pull-Down on RST The LTC2908 issues a logic low on the RST output when any one of the inputs falls below its threshold. Ideally, the RST logic output would remain low with the input supply voltage down to zero volts. Most supervisors lack pulldown capability below 1V. The LTC2908 power supply supervisor incorporates a novel low voltage pull-down circuit that can hold the RST line low with as little as 200mV of input supply voltage on V1 and/or V2 (see Figures 1 and 2). The pull-down circuit helps maintain a low impedance path to ground, reducing the risk of the RST node from floating to an indeterminate voltage. During power-up, RST starts asserting low as soon as there is at least 200mV on V1 and/or V2. The RST pulldown capability is a function of V1 and V2 as shown in the Typical Performance Characteristics. The greater of V1, V2 is the internal supply voltage (VCC) that powers the other internal circuitry. Once all the V X inputs rise above their thresholds, an internal timer is started. After the internal timer counts a 200ms delay time, RST weakly pulls high to VCC. Power-Down On power-down, once any of the V X inputs drop below their threshold, RST asserts logic low. VCC of at least 0.5V guarantees a logic low of 0.15V at RST. 10 VCC = V1 = V2 V3 = V4 = VADJ1 = VADJ2 = GND 1 Power-Up RST PULL-DOWN CURRENT, IRST (mA) RST PULL-DOWN CURRENT, IRST (mA) 10 Such an indeterminate voltage may trigger external logic causing erroneous reset operation(s). Furthermore, a mid-scale voltage level 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. RST AT 150mV 0.1 RST AT 50mV 0.01 VCC = V1 V2 = V3 = V4 = VADJ1 = VADJ2 = VADJ3 = VADJ4 = VADJ5 = GND 1 RST AT 150mV 0.1 RST AT 50mV 0.01 0.001 0.001 0 0.2 0.4 0.6 0.8 SUPPLY VOLTAGE, VCC (V) 1 2908 G16 Figure 1. RST Pull-Down Current vs Supply Voltage with 2 Inputs LTC2908-A1/ LTC2908-B1 0 1 0.2 0.4 0.6 0.8 SUPPLY VOLTAGE, VCC (V) 2908 G17 Figure 2. RST Pull-Down Current vs Supply Voltage with 1 Input 2908fc 10 LTC2908 APPLICATIONS INFORMATION The noninverting input on the VADJ comparator is set to 0.5V. And the high impedance inverting input directly ties to the VADJ pin. In a typical application, this pin connects to a tap point on an external resistive divider between the positive voltage being monitored and ground (see Figure 3). The following formula derives the value of the R1 resistor in the divider from a particular value of R2 and the desired trip voltage: V R1= TRIP – 1R2 0.5V R2 = 100k is recommended. Table 1 shows suggested 1% resistor values for various adjustable applications and their corresponding trip thresholds. Table 1. Suggested 1% Resistor Values for the VADJ Inputs VSUPPLY (V) 12 VTRIP (V) 11.25 R1 (kΩ) 2150 R2 (kΩ) 100 10 9.4 1780 100 8 7.5 6 5 3.3 3 2.5 1.8 1.5 1.2 1.0 0.9 0.8 0.7 0.6 7.5 7 5.6 4.725 3.055 2.82 2.325 1.685 1.410 1.120 0.933 0.840 0.750 0.655 0.561 1400 1300 1020 845 511 464 365 237 182 124 86.6 68.1 49.9 30.9 12.1 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 VTRIP R1 1% LTC2908-A1/LTC2908-B1/LTC2908-C1 – VADJ R2 1% + + – 0.5V In an application with less than six supply voltages, the unused supervisor inputs should be tied to the closest higher supply voltage available. Threshold Accuracy Specifying system voltage margin for worst-case operation requires the 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 ±5% 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 4.75V (5% below 5V), is the exact voltage at which a perfectly accurate supervisor generates a reset (see Figure 4). Such a perfectly accurate supervisor does not exist—the actual reset threshold may vary over a specified band (±1.5% for the LTC2908 supervisors). Figure 5 shows the typical relative threshold accuracy for all six inputs over temperature. 5.000V 4.750V ±1.5% THRESHOLD 4.675V BAND 4.600V 4.500V –5.0% –6.5% 2908 F03 –8.0% REGION OF POTENTIAL MALFUNCTION WITH 2.5% MONITOR 2908 F04 ±2.5% THRESHOLD BAND –10% 1.5 1.0 0.5 0 –0.5 –1.0 –1.5 –50 Figure 3. Setting the Adjustable Trip Point NOMINAL SUPPLY VOLTAGE MINIMUM SUPPLY IDEAL RELIABLE TOLERANCE SUPERVISOR SYSTEM THRESHOLD VOLTAGE Figure 4. Threshold Band Diagram TYPICAL THRESHOLD ACCURACY (%) Adjustable Input –25 0 25 50 TEMPERATURE (°C) 75 100 2908 F05 Figure 5. Typical Threshold Accuracy vs Temperature 2908fc 11 LTC2908 APPLICATIONS INFORMATION 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 (for example at 4.8V). Adding half of the reset threshold accuracy spread (1.5%) to the ideal 5% thresholds puts the LTC2908 thresholds at 6.5% (typ) below the nominal input voltage. For example, the 5V typical threshold is 4.675V, or 75mV below the ideal threshold of 4.750V. The guaranteed threshold lies in the band between 4.600V (8% below 5V) and 4.750V (5% below 5V) over temperature. 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 4.60V (8% below 5V). System ICs working with a ±2.5% accurate supervisor must operate down to 4.50V (10% below 5V), 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 is near the reset threshold. A less desirable but common solution to this problem is to introduce hysteresis around the nominal threshold. Notice however, this hysteresis introduces an error term in the threshold accuracy. Therefore, a ±2.5% accurate monitor with ±1% hysteresis is equivalent to a ±3.5% monitor with no hysteresis. Therefore, the LTC2908 takes a different approach to solving this problem of supply noise causing spurious reset. The first line of defense against this spurious reset is a first order lowpass filter at the output of the comparators. Therefore, each comparator output is integrated over time before triggering the output logic. Therefore, any kind of transient at the input of the comparator needs to be of sufficient magnitude and duration before it can trigger a change in the output logic. The second line of defense is the 200ms delay time tRST. This delay eliminates the effect of any supply noise, whose frequency is above 1/200ms = 5Hz, on the RST output. When any one of the supply voltages drops below its threshold, the RST pin asserts low. When the supply recovers above its threshold, the reset-pulse-generator timer starts counting. If all the supplies remain above their corresponding threshold when the timer finishes counting, the RST pin weakly pulls high. However, if any of the supplies falls below its threshold any time during the period when the timer is still counting, the timer resets and it starts fresh when all the supplies rise above their corresponding threshold. Note that this second line of defense is only effective for a rising supply and does not affect the sensitivity of the system to a falling supply. Therefore, the first line of defense that works for both cases of rising and falling is necessary. These two approaches prevent spurious reset caused by supply noise without sacrificing the threshold accuracy. Although all six comparators for the six inputs have builtin glitch filtering, use bypass capacitors on the V1 and V2 inputs because the greater of V1 or V2 supplies the VCC for the part (a 0.1μF ceramic capacitor satisfies most applications). Apply filter capacitors on the V3, V4, VADJ1, VADJ2, VADJ3, VADJ4 and VADJ5 inputs in extremely noisy situations. 2908fc 12 LTC2908 APPLICATIONS INFORMATION RST Output Characteristics The DC characteristics of the RST pull-up and pull-down strength are shown in the Typical Performance Characteristics section. The RST output has a weak internal pull-up to VCC = Max(V1, V2) and a strong pull-down to ground. The weak pull-up and strong pull-down arrangement allows this pin to have open-drain behavior while possessing several other beneficial characteristics. The weak pull-up eliminates the need for external pull-up resistors when the rise time on these pins is not critical. On the other hand, the open-drain RST behavior allows for wired-OR connections and can be useful when more than one signal needs to pull down on the RST line. As noted in the discussion of power-up and power-down, the circuits that drive RST are powered by VCC. During fault condition, VCC of at least 0.5V guarantees a maximum VOL = 0.15V at RST. Output Rise and Fall Time Estimation The following formula estimates the output fall time (90% to 10%) for a particular external load capacitance (CLOAD): tFALL ≈ 2.2 • RPD • CLOAD where RPD is the on-resistance of the internal pull-down transistor estimated to be typically 40Ω at room temperature (25°C) and CLOAD is the external load capacitance on the pin. Assuming a 150pF load capacitance, the fall time is about 13ns. The rise time on the RST pin is limited by a weak internal pull-up current source to VCC. The following formula estimates the output rise time (10% to 90%) at the RST pin: tRISE ≈ 2.2 • RPU • CLOAD where RPU is the on-resistance of the pull-up transistor. Notice that this pull-up transistor is modeled as a 6μA current source in the Block Diagram as a typical representation. The on-resistance as a function of the VCC = Max(V1, V2) voltage (for VCC > 1V) at room temperature is estimated as follows: 6 • 105 RPU = Ω MAX ( V1,V2) – 1V At VCC = 3.3V, RPU is about 260k. Using 150pF for load capacitance, the rise time is 86μs. A smaller external pull-up resistor may be used if the output needs to pull up faster and/or to a higher voltage. For example, the rise time reduces to 3.3μs for a 150pF load capacitance when using a 10k pull-up resistor. TYPICAL APPLICATIONS Six Supply Monitor, 5% Tolerance, 12V, 5V, 3.3V, 2.5V, 1.8V, 1V 12V DC/DC DC/DC DC/DC DC/DC DC/DC 5V 3.3V SYSTEM 2.5V 1.8V 1.0V C1 C2 0.1μF 0.1μF V1 R1 2.15M R3 R2 100k 86.6k V2 V3 V4 VADJ1 LTC2908-A1 GND R4 100k VADJ2 RST 2908 TA02 2908fc 13 LTC2908 TYPICAL APPLICATIONS Quad Supply Monitor with One Adjustable Input, 5% Tolerance, 3.3V, 2.5V, 1.8V, 1.2V 3.3V DC/DC DC/DC DC/DC 2.5V SYSTEM 1.8V 1.2V C1 C2 0.1μF 0.1μF V1 R3 124k V2 V3 V4 VADJ1 LTC2908-B1 GND R4 100k VADJ2 RST 2908 TA03 Pin Programmable Dual Supply Monitor with Possible Future Expansion up to Six Supplies, 5% Tolerance, 3.3V and 2.5V 3.3V DC/DC SYSTEM 2.5V C2 0.1μF C1 0.1μF V1 V2 V3 V4 LTC2908-B1 GND VADJ1 VADJ2 RST 2908 TA05 Six Supply Monitor, 5% Tolerance 12V, 2.5V, 1.8V, 1.5V, 1.2V, 1.0V 12V DC/DC DC/DC DC/DC DC/DC DC/DC 2.5V 1.8V SYSTEM 1.5V 1.2V 1.0V C1 0.1μF R1 2.15M V1 R3 R2 100k 237k VADJ1 R4 100k VADJ2 R5 182k R6 100k VADJ3 LTC2908-C1 GND R7 124k R9 R8 100k 86.6k VADJ4 R10 100k VADJ5 RST 2908 TA06 2908fc 14 LTC2908 PACKAGE DESCRIPTION DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702 Rev B) 0.61 ±0.05 (2 SIDES) 3.00 ±0.10 (2 SIDES) R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 0.70 ±0.05 2.55 ±0.05 1.15 ±0.05 PACKAGE OUTLINE 2.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.25 ± 0.05 0.56 ± 0.05 (2 SIDES) 0.75 ±0.05 0.200 REF 0.50 BSC 2.20 ±0.05 (2 SIDES) 1 (DDB8) DFN 0905 REV B 0.50 BSC 2.15 ±0.05 (2 SIDES) 0 – 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 4 0.25 ± 0.05 PIN 1 R = 0.20 OR 0.25 × 45° CHAMFER BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. 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 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.52 MAX 2.90 BSC (NOTE 4) 0.65 REF 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.22 – 0.36 8 PLCS (NOTE 3) 0.65 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 0.09 – 0.20 (NOTE 3) 1.95 BSC TS8 TSOT-23 0802 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 2908fc 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 LTC2908 TYPICAL APPLICATION Six Supply Monitor with Manual Reset Button, 5% Tolerance, 12V, 5V, 3.3V, 2.5V, 1.8V, 1.5V 12V (VTRIP = 11.25V) DC/DC DC/DC DC/DC DC/DC DC/DC 5V (VTRIP = 4.675V) 3.3V (VTRIP = 3.086V) SYSTEM 2.5V (VTRIP = 2.338V) 1.8V (VTRIP = 1.685V) 1.5V (VTRIP = 1.410V) C1 C2 0.1μF 0.1μF R1 182k R2 100k R3 MANUAL 2.15M RESET BUTTON R5* (NORMALLY OPEN) 10k R4 100k V1 *OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE V2 V3 V4 VADJ1 LTC2908-A1 GND VADJ2 RST 2908 TA04 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/LTC1326-2.5 Micropower Precision Triple Supply Monitor for 5V/2.5V, 3.3V and ADJ 4.725V, 3.118V, 1V Threshold (±0.75%)and ADJ LTC1536 Precision Triple Supply Monitor for PCI Applications Meets PCI tFAIL Timing Specifications LTC1726-2.5/LTC1726-5 Micropower Triple Supply Monitor for 2.5V/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 and DFN Packages LTC2901 Programmable Quad Supply Monitor Adjustable Reset and Watchdog Timer, 16-Lead SSOP Package LTC2902 Programmable Quad Supply Monitor Adjustable Reset and Tolerance, 16-Lead SSOP Package LTC2903 Precision Quad Supply Monitor 6-Lead SOT-23 Package LTC2904 Three-State Programmable Precision Dual Supply Monitor Adjustable Tolerance, 8-Lead SOT-23 and DFN Packages LTC2905 Three-State Programmable Precision Dual Supply Monitor Adjustable Reset and Tolerance, 8-Lead SOT-23 and DFN Packages LTC2906 Dual Supply Monitor with One Pin Selectable Threshold and One Adjustable Input 0.5V Adjustable Threshold and Three Supply Tolerances, 8-Lead SOT-23 and DFN Packages LTC2907 Dual Supply Monitor with One Pin Selectable Threshold and One Adjustable Input 0.5V Adjustable Threshold, Reset and Three Supply Tolerances, 8-Lead SOT-23 and DFN Packages LTC2909 Precision Triple/Dual Input UV, OV and Negative Voltage Monitor Shunt Regulated VCC Pin, Adjustable Threshold and Reset, 8-Lead SOT-23 and DFN Packages 2908fc 16 Linear Technology Corporation LT 0708 REV C • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2004