LTC2909 Precision Triple/Dual Input UV, OV and Negative Voltage Monitor U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Two Low Voltage Adjustable Inputs (0.5V) Pin Selectable Input Polarity Allows Negative and OV Monitoring Guaranteed Threshold Accuracy: ±1.5% 6.5V Shunt Regulator for High Voltage Operation Low 50µA Quiescent Current Buffered 1V Reference for Negative Supply Offset Input Glitch Rejection Adjustable Reset Timeout Period Selectable Internal Timeout Saves Components Open-Drain ⎯R⎯S⎯T Output Accurate UVLO for 2.5V, 3.3V, 5V Systems Ultralow Voltage Reset: VCC = 0.5V Guaranteed Space Saving 8-Lead TSOT-23 and 3mm × 2mm DFN Packages U APPLICATIO S ■ ■ ■ ■ The two inputs have a nominal 0.5V threshold, featuring tight 1.5% threshold accuracy over the entire operating temperature range. Glitch filtering ensures reliable reset operation without false triggering. A third fixed-threshold UVLO monitor on the part’s VCC (also 1.5% accuracy) is available for standard logic supplies. The common reset output has a timeout that may use a preset 200ms, be set by an external capacitor or be disabled. A three-state input pin sets the input polarity of each adjustable input without requiring any external components. The LTC2909 provides a highly versatile, precise, spaceconscious, micropower solution for supply monitoring. Desktop and Notebook Computers Handheld Devices Network Servers Core, I/O Monitor Automotive , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U ■ The LTC®2909 is a dual input monitor intended for a variety of system monitoring applications. Polarity selection and a buffered reference output allow the LTC2909 to monitor positive and negative supplies for undervoltage (UV) and overvoltage (OV) conditions. TYPICAL APPLICATIO 3.3V UV/OV (Window) Monitor Application with 200ms Internal Timeout (3.3V Logic Out) SEL Pin Connection for Input Polarity Combinations CBYP 100nF POLARITY 3.3V RP6 453k RPU 10k ADJ1 ADJ2 SEL PIN + + VCC SEL + – OPEN TMR – – GND VCC RST ADJ1 LTC2909-2.5 RP5 10.7k REF ADJ2 RP4 76.8k FAULT OUTPUT GND 2909 TA01a 2909fa 1 LTC2909 U W W W ABSOLUTE AXI U RATI GS (Notes 1, 2) Terminal Voltages VCC (Note 3)............................................. –0.3V to 6V SEL, ⎯R⎯S⎯T .............................................. –0.3V to 7.5V ADJ1, ADJ2 .......................................... –0.3V to 7.5V TMR ..........................................–0.3V to (VCC + 0.3V) Terminal Currents IVCC (Note 3) ....................................................±10mA IREF ....................................................................±1mA Operating Temperature Range LTC2909C ................................................ 0°C to 70°C LTC2909I .............................................– 40°C to 85°C Storage Temperature Range DFN....................................................– 65°C to 125°C TSOT-23.............................................– 65°C to 150°C Lead Temperature (Soldering, 10 sec) TSOT-23............................................................ 300°C U W U PACKAGE/ORDER I FOR ATIO TOP VIEW SEL 1 TMR 2 VCC 3 RST 4 9 8 ADJ1 7 ADJ2 6 REF 5 GND DDB PACKAGE 8-LEAD (3mm ´ 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 76°C/W EXPOSED PAD (PIN 9) MAY BE LEFT OPEN OR TIED TO GND (PCB CONNECTION REQUIRED FOR STATED θJA) TOP VIEW ADJ1 1 ADJ2 2 REF 3 GND 4 8 SEL 7 TMR 6 VCC 5 RST TS8 PACKAGE 8-LEAD PLASTIC TSOT-23 TJMAX = 125°C, θJA = 250°C/W ORDER PART NUMBER DDB PART* MARKING LTC2909CDDB-2.5 LTC2909IDDB-2.5 LTC2909CDDB-3.3 LTC2909IDDB-3.3 LTC2909CDDB-5 LTC2909IDDB-5 LBXG LBXG LBZS LBZS LBZT LBZT ORDER PART NUMBER TS8 PART* MARKING LTC2909CTS8-2.5 LTC2909ITS8-2.5 LTC2909CTS8-3.3 LTC2909ITS8-3.3 LTC2909CTS8-5 LTC2909ITS8-5 LTBXF LTBXF LTBZV LTBZV LTBZW LTBZW Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges. 2909fa 2 LTC2909 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 2.5V (LTC2909-2.5), VCC = 3.3V (LTC2909-3.3), VCC = 5V (LTC2909-5), ADJ1 = ADJ2 = 0.55V, SEL = floating, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS VCC(MIN) Operating Supply Voltage ⎯R⎯S⎯T in Correct State ● MIN 0.5 VCC(SHUNT) VCC Shunt Regulation Voltage IVCC = 1mA, IVREF = 0 ● 6.0 ICC VCC Input Current 2.175 < VCC < 6V ● VRT ADJ Input Threshold ● ΔVRT ADJ Hysteresis (Note 4) TMR = VCC IADJ ADJ Input Current VADJ = 0.55V ● VCC(UVLO) VCC UVLO Threshold LTC2909-2.5 LTC2909-3.3 LTC2909-5 ● ● ● ΔVCC(UVLO) UVLO Hysteresis (Note 4) TMR = VCC VREF Buffered Reference Voltage VCC > 2.175V, IVREF = ±1mA ITMR(UP) TMR Pull-Up Current ITMR(DOWN) t⎯R⎯S⎯T(EXT) TYP MAX UNITS V 6.5 6.9 V 50 150 µA 0.492 0.500 0.508 V 1.5 3.5 10.0 mV ±15 nA 2.175 2.871 4.350 2.213 2.921 4.425 2.250 2.970 4.500 V V V 0.3 0.7 2.0 % ● 0.985 1.000 1.015 V VTMR = 1V ● –1.5 –2.1 –2.7 µA TMR Pull-Down Current VTMR = 1V ● 1.5 2.1 2.7 µA Reset Timeout Period, External CTMR = 2.2nF ● 16 20 25 ms t⎯R⎯S⎯T(INT) Reset Timeout Period, Internal VTMR = 0V ● 150 200 260 ms VTMR(DIS) Timer Disable Voltage VTMR Rising ● VCC – 0.36 VCC – 0.25 VCC – 0.16 ΔVTMR(DIS) Timer Disable Hysteresis VTMR Falling ● 60 110 150 mV VTMR(INT) Timer Internal Mode Voltage VTMR Falling ● 0.14 0.21 0.27 V ΔVTMR(INT) Timer Internal Mode Hysteresis VTMR Rising ● 40 70 110 mV tPROP ADJx Driven Beyond Reset Threshold (VRTX) by 5mV ● 50 150 500 µs tUV ADJx Comparator Propagation Delay to ⎯R⎯S⎯T VCC Undervoltage Detect to ⎯R⎯S⎯T VCC Less Than UVLO Threshold (VCC(UVLO)) by 1% ● 50 150 500 µs VOL(⎯R⎯S⎯T) ⎯R⎯S⎯T Output Voltage Low VCC = 0.5V, I = 5µA VCC = 1V, I = 100µA VCC = 3V, I = 2500µA ● ● ● 0.01 0.01 0.10 0.15 0.15 0.30 V V V IOH(⎯R⎯S⎯T) ⎯R⎯S⎯T Output Voltage High Leakage ⎯R⎯S⎯T = VCC ● ±1 µA 0.4 V V Three-State Input SEL VIL Low Level Input Voltage ● VIH High Level Input Voltage ● VZ Pin Voltage when Left in Open State ISEL(Z) Allowable Leakage in Open State ISEL SEL Input Current 1.4 ISEL = 0µA 0.9 ● SEL = VCC or SEL = GND 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 reliability and lifetime. Note 2: All currents into pins are positive; all voltages are referenced to GND unless otherwise noted. Note 3: VCC maximum pin voltage is limited by input current. Since the VCC pin has an internal 6.5V shunt regulator, a low impedance supply V ● V ±5 ±10 µA µA ±25 µA which exceeds 6V may exceed the rated terminal current. Operation from higher voltage supplies requires a series dropping resistor. See Applications Information. Note 4: Threshold voltages have no hysteresis unless the part is in comparator mode. Hysteresis is one-sided, affecting only invalid-to-valid transitions. See Applications Information. 2909fa 3 LTC2909 U W 506 504 502 500 498 496 494 492 –50 –25 0 50 75 25 TEMPERATURE (°C) 100 125 1.5 0.015 1.0 1.010 0.5 0 –0.5 –1.5 –50 –25 50 25 75 0 TEMPERATURE (°C) 1.015 TA = 125°C TA = –40°C TA = 25°C TA = –40°C 0.995 0.995 0.990 0.990 0.985 0.985 2 1 2.5 4.5 5 3 3.5 4 SUPPLY VOLTAGE, VCC (V) 5.5 Allowable Glitch Duration vs Magnitude RESET OCCURS ABOVE CURVE 200 100 0 0.1 1 10 100 GLITCH PERCENTAGE PAST THRESHOLD (%) 2909 G07 100 VCC = 5V VCC = 3.3V 45 40 VCC = 2.5V 35 30 25 –25 0 50 75 25 TEMPERATURE (°C) 100 125 Reset Timeout Period vs Temperature 260 1000 100 10 1 0.1 125 2909 G06 RESET TIMEOUT PERIOD, tRST (ms) RESET TIMEOUT PERIOD, tRST (ms) 500 300 ADJ1 = 0.55V 55 ADJ2 = 0.45V SEL = OPEN 50 20 –50 6 10000 600 50 25 75 0 TEMPERATURE (°C) 2909 G03 External Timeout Period vs Capacitance 700 –25 2909 G05 2909 G04 400 0.985 –50 60 1.000 1.000 –0.5 0 0.5 LOAD CURRENT, IREF (mA) 0.995 Quiescent Supply Current vs Temperature TA = 125°C 1.005 TA = 25°C MAXIMUM ALLOWABLE GLITCH DURATION (µs) 125 IREF = 0A REF VOLTAGE, VREF (V) REF VOLTAGE, VREF (V) 100 1.010 –1 1.000 REF Output Line Regulation 1.010 1.005 1.005 2909 G02 REF Output Load Regulation VCC = 2.5V IREF = 0A 0.990 –1.0 2909 G01 1.015 REF Output Voltage vs Temperature QUIESCENT SUPPLY CURRENT, ICC (µA) THRESHOLD VOLTAGE, VRT (mV) 508 VCC UVLO Threshold Variation vs Temperature REF VOLTAGE, VREF (V) ADJ Threshold Voltage vs Temperature THRESHOLD VOLTAGE VARIATION (% OF 25°C VALUE) TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted 1 10 100 TMR PIN CAPACITANCE, CTMR (nF) 1000 2909 G08 240 EXTERNAL WITH 22nF CAPACITOR 220 INTERNAL 200 180 160 140 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 2909 G09 2909fa 4 LTC2909 U W TYPICAL PERFOR A CE CHARACTERISTICS Shunt Regulation Voltage vs Supply Current 6.8 ICC = 10mA 6.6 ICC = 1mA ICC = 100µA 6.4 6.2 6.0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 7.0 ⎯R⎯S⎯T Output Voltage vs VCC 5 TA = 25°C ADJ1 = 0.55 ADJ2 = 0.45 4 SEL = OPEN 10k PULL-UP R TO VCC 6.8 RST VOLTAGE (V) 7.0 SHUNT REGULATION VOLTAGE, VCC(SHUNT) (V) 6.6 6.4 2 LTC2909-2.5 LTC2909-3.3 0 6.0 0.01 0.1 1 10 SUPPLY CURRENT, ICC (mA) 100 PULL-DOWN CURRENT, IRST (mA) RST WITH 10k PULL-UP 0.1 RST WITH 100k PULL-UP 1 ADJ1 = 0.55 ADJ2 = 0.55 5 SEL = OPEN 4 RST AT 150mV 3 2 0.1 0.2 0.3 0.4 0.5 0.6 0.7 SUPPLY VOLTAGE, VCC (V) 0 0.8 1 5 2 3 4 SUPPLY VOLTAGE, VCC (V) RST AT 50mV 0.01 0.0001 0.2 0.4 0.6 0.8 SUPPLY VOLTAGE, VCC (V) 0 ⎯R⎯S⎯T VOL vs I⎯R⎯S⎯T ISEL vs Temperature –20 VCC = 3V NO PULL-UP R 0.8 1 2909 G15 2909 G14 2909 G13 1.0 RST AT 150mV 0.1 0.001 RST AT 50mV 1 0 0 0 5 ⎯R⎯S⎯T Pull-Down Current vs VCC 6 0.4 0.2 3 4 2 SUPPLY VOLTAGE, VCC (V) 2909 G12 ⎯R⎯S⎯T Pull-Down Current vs VCC VCC 1 0 2909 G11 ⎯R⎯S⎯T Output Voltage vs VCC 0.3 LTC2909-5 1 2909 G10 RST VOLTAGE (V) 3 6.2 PULL-DOWN CURRENT, IRST (mA) SHUNT REGULATION VOLTAGE, VCC(SHUNT) (V) Shunt Regulation Voltage vs Temperature TA = 25°C unless otherwise noted ISEL vs Temperature 20 SEL = GND –18 18 –16 16 SEL = VCC TA = –40°C 0.4 –14 –12 0.2 0 ISEL (µA) TA = 25°C 0.6 ISEL (µA) RST VOL (V) TA = 125°C 0 5 10 15 20 IRST (mA) 25 30 1635 G07 –10 –50 14 12 –25 50 25 0 75 TEMPERATURE (°C) 100 125 2909 G17 10 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 2909 G18 2909fa 5 LTC2909 U U U PI FU CTIO S (TSOT-23/DFN Package) ADJ1 (Pin 1/Pin 8): Adjustable Voltage Input 1. Input to voltage monitor comparator 1 (0.5V nominal threshold). The polarity of the input is selected by the state of the SEL pin (refer to Table 1). Tie to REF if unused (with SEL = VCC or Open). ADJ2 (Pin 2/Pin 7): Adjustable Voltage Input 2. Input to voltage monitor comparator 2 (0.5V nominal threshold). The polarity of the input is selected by the state of the SEL pin (refer to Table 1). Tie to GND if unused (with SEL = GND or Open). REF (Pin 3/Pin 6): Buffered Reference Output. 1V nominal reference used for the offset of negative-monitoring applications. The buffered reference can source and sink 1mA. The reference can drive a capacitive load of up to 1000pF. Larger capacitance may degrade transient performance. This pin does not require a bypass capacitor, nor is one recommended. Leave open if unused. GND (Pin 4/Pin 5): Device Ground. ⎯ S ⎯ T⎯ (Pin 5/Pin 4): Open-Drain Inverted Reset Logic Output. R Asserts low when any positive polarity input voltage is below threshold or any negative polarity input voltage is above threshold or VCC is below UVLO threshold. Held low for a timeout after all voltage inputs are valid. Requires an external pull-up resistor and may be pulled above VCC. VCC (Pin 6/Pin 3): Power Supply. Bypass this pin to ground with a 0.1μF (or greater) capacitor. Operates as a direct supply input for voltages up to 6V. Operates as a shunt regulator for supply voltages greater than 6V and should have a resistor between this pin and the supply to limit VCC input current to no greater than 10mA. When used without a current-limiting resistor, pin voltage must not exceed 6V. UVLO options allow VCC to be used as an accurate third fixed 10% UV supply monitor. TMR (Pin 7/Pin 2): Reset Timeout Control. Attach an external capacitor (CTMR) to GND to set a reset timeout of 9ms/nF. A low leakage ceramic capacitor is recommended for timer accuracy. Capacitors larger than 1μF (9 second timeout) are not recommended. See Applications Information for further details. Leaving this pin open generates a minimum timeout of approximately 400μs. A 2.2nF capacitor will generate a 20ms timeout. Tying this pin to ground will enable the internal 200ms timeout. Tying this pin to VCC will disable the reset timer and put the part in comparator mode. Signals from the comparator outputs will then go directly to ⎯R⎯S⎯T. SEL (Pin 8/Pin 1): Input Polarity Select Three-State Input. Connect to VCC, GND or leave unconnected in open state to select one of three possible input polarity combinations (refer to Table 1). Exposed Pad (Pin 9, DFN Only): The Exposed Pad may be left unconnected. For better thermal contact, tie to a PCB trace. This trace must be grounded or unconnected. 2909fa 6 LTC2909 W BLOCK DIAGRA SEL VCC VCC THREE-STATE DECODE CONTROL 2 ADJ1 6.5V CONTROL 1 + TMR – ADJ2 ADJUSTABLE PULSE GENERATOR + THREE-STATE DECODE RST GND 200ms PULSE GENERATOR – VCC + – + – SEL GND OPEN VCC 500mV + REF + – 1.000V CONTROL 1 H L L CONTROL 2 H H L – 2909 BD WU W TI I G DIAGRA S Normal Positive Polarity Input Timing VADJ VRT VADJ tPROP RST Comparator Mode Positive Polarity Input Timing tRST 1V tPROP VRT RST tRST 1V tPROP Comparator Mode Negative Polarity Input Timing VADJ tPROP VRT tPROP tPROP Normal UVLO Timing RST 1V Comparator Mode UVLO Timing VCC VCC(UVLO) tUV ,VRT 1V RST VCC VCC(UVLO) ,VRT 1V RST Normal Negative Polarity Input Timing VADJ VRT tRST tUV RST ,VCC(UVLO) tUV 1V 2909 TD 2909fa 7 LTC2909 U W U U APPLICATIO S I FOR ATIO The LTC2909 is a low power, high accuracy dual/triple supply monitor with two adjustable inputs and an accurate UVLO. Reset timeout may be selected with an external capacitor, set to an internally generated 200ms, or disabled entirely. The three-state polarity select pin (SEL) chooses one of three possible polarity combinations for the adjustable input thresholds, as described in Table 1. Both input voltages (VADJ1 and VADJ2) must be valid (above threshold if configured for positive polarity, below threshold if configured for negative polarity), and VCC above the UVLO threshold for the reset timeout before ⎯R⎯S⎯T is released. The LTC2909 asserts the reset output during power-up, power-down and brownout conditions on any of the voltage inputs. Power-Up The LTC2909 uses proprietary low voltage drive circuitry for the ⎯R⎯S⎯T pin which holds ⎯R⎯S⎯T low with as little as 200mV of VCC. This helps prevent an unknown voltage on the ⎯R⎯S⎯T line during power-up. In applications where the low voltage pull-down capability is important, the supply to which the external pull-up resistor connects should be the same supply which powers the part. Using the same supply for both ensures that ⎯R⎯S⎯T never floats above 200mV during power-up, as the pulldown ability of the pin will then increase as the required pull-down current to maintain a logic low increases. Once VCC passes the UVLO threshold, polarity selection and timer initialization will occur. If the monitored supplies (ADJ1 and ADJ2) are valid, the appropriate timeout delay will begin, after which ⎯R⎯S⎯T will be released. Otherwise, the part will wait until all supplies are valid (including VCC above the UVLO threshold) before beginning the timeout. Power-Down On power-down, once VCC drops below the UVLO threshold or either VADJ becomes invalid, ⎯R⎯S⎯T asserts logic low. VCC of at least 0.5V guarantees a logic low of 0.15V at ⎯R⎯S⎯T. Shunt Regulator The LTC2909 contains an internal 6.5V shunt regulator on the VCC pin to allow operation from a high voltage supply. To operate the part from a supply higher than 6V, the VCC pin must have a series resistor, RCC, to the supply. This resistor should be sized according to the following equation: VS(MAX ) – 6.2V 10mA ≤ RCC ≤ VS(MIN) – 6.8V 200µA + IVREF where VS(MIN) and VS(MAX) are the operating minimum and maximum of the supply, and IVREF is the maximum current the user expects to draw from the reference output. As an example, consider operation from an automobile battery which might dip as low as 10V or spike to 60V. Assume that the user will be drawing 100μA from the reference. We must then pick a resistance between 5.4k and 10.7k. When the VCC pin is connected to a low impedance supply, it is important that the supply voltage never exceed 6V, or the shunt regulator may begin to draw large currents. Some supplies may have nominal value sufficiently close to the shunt regulation voltage to prevent sizing of the resistor according to the above equation. For such supplies, a 470Ω series resistor may be used. Polarity Selection The external connection of the SEL pin selects the polarities of the LTC2909 adjustable inputs. SEL may be connected to GND, connected to VCC or left unconnected during normal operation. When left unconnected, the maximum leakage allowable from the pin to either GND or VCC is 10μA. Table 1 shows the three possible selections of polarity based on SEL connection. Table 1. Voltage Threshold Selection ADJ1 INPUT ADJ2 INPUT SEL Positive Polarity (+) UV or (–) OV Positive Polarity (+) UV or (–) OV VCC Positive Polarity (+) UV or (–) OV Negative Polarity (–) UV or (+) OV Open Negative Polarity (–) UV or (+) OV Negative Polarity (–) UV or (+) OV Ground Note: Open = open circuit or driven by a three-state buffer in high impedance state with leakage current less than 10μA. If the user’s application requires, the SEL pin may be driven using a three-state buffer which satisfies the VIL, VIH and leakage of the three-state pin. 2909fa 8 LTC2909 U U W U APPLICATIO S I FOR ATIO If the state of the SEL pin configures a given input as “negative polarity,” the voltage at the ADJx pin must be below the trip point (0.5V nominal), or the ⎯R⎯S⎯T output will be pulled low. Conversely, if a given input is configured as “positive polarity,” the pin voltage must be above the trip point or ⎯R⎯S⎯T will assert low. Thus, a “negative polarity” input may be used to determine whether a monitored negative voltage is smaller in absolute value than it should be (–UV), or a monitored positive voltage is larger than it should be (+OV). The opposite is true for a “positive polarity” input (–OV or +UV). These usages are also shown in Table 1. For purposes of this data sheet, a negative voltage is considered “undervoltage” if it is closer to ground than it should be (e.g., –4.3V for a –5V supply). Proper configuration of the SEL pin and setting of the trip-points via external resistors allows for any two fault conditions to be detected. For example, the LTC2909 may monitor two supplies (positive, negative or one of each) for UV or for OV (or one UV and one OV). It may also monitor a single supply (positive or negative) for both UV and OV. Tables 2a and 2b show example configurations for monitoring possible combinations of fault condition and supply polarity. Table 2a. Possible Combinations of Supply Monitoring. For Example Purposes, All Supplies are Monitored at 5% Tolerance and Connections are Shown Only for ADJ1, ADJ2, REF, SEL SEL = GND SEL = VCC 15V (UV) 5V (UV) RP2A 3.09M –15V (UV) –5V (UV) RP2B 1.15M RN2A 3.09M RN2B 1.37M ADJ1 ADJ2 RP1A 115k ADJ1 SEL ADJ2 RN1A 107k RP1B 137k REF REF 2 Positive UV 2 Negative UV –15V (OV) –5V (OV) RN2A 10.2M 15V (OV) 5V (OV) RN2B 1.37M RP2A 6.19M RP2B 1.33M ADJ1 ADJ2 RN1A 309k ADJ1 SEL RN1B 118k ADJ2 RP1A 200k REF 2 Negative OV 2 Positive OV 15V (UV) –15V (OV) 15V (OV) –15V (UV) RN2 10.2M RP2 6.19M RN2 3.09M ADJ1 ADJ2 RP1 115k SEL RP1B 137k REF RP2 3.09M SEL RN1B 133k ADJ1 SEL RN1 309k ADJ2 RP1 200k REF 1 Positive UV, 1 Negative OV SEL RN1 107k REF 1 Positive OV, 1 Negative UV 2909fa 9 LTC2909 U U W U APPLICATIO S I FOR ATIO Table 2b. Possible Combinations of Supply Monitoring. For Example Purposes, All Supplies are Monitored at 5% Tolerance and Connections are Shown Only for ADJ1, ADJ2, REF, SEL SEL OPEN 15V (UV/OV) –15V (UV/OV) RP6 2.37M RN6 10.2M ADJ1 RP5 10.7k ADJ2 ADJ1 RN5 40.2k SEL ADJ2 REF REF 1 Negative UV and OV 1 Positive UV and OV –15V (OV) 15V (OV) 15V (UV) –15V (UV) RP2 3.09M RN2 3.09M RN2 10.2M RP2 6.19M ADJ1 ADJ1 ADJ2 RP1 115k ADJ2 SEL RN1 309k RN1 107k REF 1 Positive UV, 1 Negative UV 15V (UV) 5V (OV) 1 Negative OV, 1 Positive OV –15V (OV) –5V (UV) RP2B 1.33M RN2A 10.2M RN2B 1.37M ADJ1 ADJ2 RP1A 115k SEL RP1 200k REF RP2A 3.09M SEL RN4 309k RP4 76.8k ADJ1 SEL RP1B 137k REF 1 Positive UV, 1 Positive OV Adjust Input Trip Point The trip threshold for the supplies monitored by the adjustable inputs is set with an external resistor divider, allowing the user complete control over the trip point. Selection of this trip voltage is crucial to the reliability of the system. Any power supply has some tolerance band within which it is expected to operate (e.g., 5V ±10%). It is generally undesirable that a supervisor issue a reset when the power supply is inside this tolerance band. Such a “nuisance” reset reduces reliability by preventing the system from functioning under normal conditions. To prevent nuisance resets, the supervisor threshold must be guaranteed to lie outside the power supply tolerance ADJ2 RN1A 309k SEL RN1B 133k REF 1 Negative UV, 1 Negative OV band. To ensure that the threshold lies outside the power supply tolerance range, the nominal threshold must lie outside that range by the monitor’s accuracy specification. All three of the LTC2909 inputs (ADJ1, ADJ2, VCC UVLO) have the same relative threshold accuracy of ±1.5% of the programmed nominal input voltage (over the full operating temperature range). Therefore, using the LTC2909, the typical 10% UV threshold is at 11.5% below the nominal input voltage level. For a 5V input, the threshold is nominally 4.425V. With ±1.5% accuracy, the trip threshold range is 4.425V ±75mV over temperature (i.e., 10% to 13% below 5V). The monitored system must thus operate reliably down to 4.35V or 13% below 5V over temperature. 2909fa 10 LTC2909 U W U U APPLICATIO S I FOR ATIO The above discussion is concerned only with the DC value of the monitored supply. Real supplies also have relatively high frequency variation from sources such as load transients, noise and pickup. These variations should not be considered by the monitor in determining whether a supply voltage is valid or not. The variations may cause spurious outputs at ⎯R⎯S⎯T, particularly if the supply voltage is near its trip threshold. A common solution to the problem of spurious reset is to introduce hysteresis around the nominal threshold. However, this hysteresis degrades the effective accuracy of the monitor and increases the range over which the system must operate. The LTC2909 therefore does not have hysteresis, except in comparator mode (see Setting the Reset Timeout). If hysteresis is desired in other modes, it may be added externally. See Typical Applications for an example. lowpass filter with the resistor divider will further reject high frequency components of the supply, at the cost of slowing the monitor’s response to fault conditions. Selecting External Resistors In a typical positive supply monitoring application, the ADJx pin connects to a tap point on an external resistive divider between a positive voltage being monitored and ground, as shown in Figure 1. When monitoring a negative supply, the ADJx pin connects to a tap point on a resistive divider between the negative voltage being monitored and the buffered reference (REF), as shown in Figure 2. VMON RP2 The LTC2909 uses two techniques to combat spurious reset without sacrificing threshold accuracy. First, the timeout period helps prevent high frequency variation whose frequency is above 1/ tRST from appearing at the ⎯R⎯S⎯T output. The combination of the reset timeout and comparator filtering prevents spurious changes in the output state without sacrificing threshold accuracy. If further supply glitch immunity is needed, the user may place an external capacitor from the ADJ input to ground. The resultant RC + RP1 – 0.5V + – 2909 F01 When either ADJ1 or ADJ2 becomes invalid, the ⎯R⎯S⎯T pin asserts low. When the supply recovers past the threshold, the reset timer starts (assuming it is not disabled) and ⎯R⎯S⎯T does not go high until it finishes. If the supply becomes invalid any time during the timeout period, the timer resets and starts fresh when the supply next becomes valid. While the reset timeout is useful at preventing toggling of the reset output in most cases, it is not effective at preventing nuisance resets due to short glitches (from load transients or other effects) on a valid supply. To reduce sensitivity to these short glitches, the comparator outputs go through a lowpass filter before triggering the output logic. Any transient at the input of a comparator needs to be of sufficient magnitude and duration to pass the filter before it can change the monitor state. ADJx Figure 1. Setting Positive Supply Trip Point REF RN1 ADJx + RN2 – VMON 0.5V + – 2909 F02 Figure 2. Setting Negative Supply Trip Point Normally the user will select a desired trip voltage based on their supply and acceptable tolerances, and a value of RN1 or RP1 based on current draw. Current used by the resistor divider will be approximately: I= 0.5V R X1 Recommended range is 1k to 1M. 2909fa 11 LTC2909 U U W U APPLICATIO S I FOR ATIO For a positive-monitoring application, RP2 is then chosen by: REF ADJ1 RP2 = RP1(2VTRIP – 1) For a negative-monitoring application: RN4 RN2 = RN1(1 – 2VTRIP) RN5 Note that the value VTRIP should be negative for a negative application. The LTC2909 can also be used to monitor a single supply for both UV and OV. This may be accomplished with three resistors, instead of the four required for two independent supplies. Configurations are shown in Figures 3 and 4. RP4 or RN4 may be chosen as is RP1 above. For a given RP4, monitoring a positive supply: RP5 = RP 4 VOV – VUV VUV RP6 = RP 4 ( 2VUV – 1) VOV VUV VUV – VOV 1 – VUV RN6 = RN4 (1 – 2VUV ) 1 – VOV 1 – VUV For example, consider monitoring a –5V supply at ±10%. For this supply application: VOV = –5.575V and VUV = –4.425V. ADJ1 + VMON RP6 RP5 + RN6 – VMON 0.5V + – 2909 F04 Figure 4. Setting UV and OV Trip Point for a Negative Supply Suppose we wish to consume about 5μA in the divider, so RN4 = 100k. We then find RN5 = 21.0k, RN6 = 1.18M (nearest 1% standard values have been chosen). Suggested values of resistors for 5% monitoring are shown in Table 3. The LTC2909 contains an accurate third 10% undervoltage monitor on the VCC pin. This monitor is fixed at a nominal 11.5% below the VCC specified in the part number. The standard part (LTC2909-2.5) is configured to monitor a 2.5V supply (UVLO threshold of 2.213V), but versions to monitor 3.3V and 5.0V (UVLO of 2.921V and 4.425V, respectively) are available. For applications that do not need VCC monitoring, the 2.5V version should be used, and the UVLO will simply guarantee that the VCC is above the minimum required for proper threshold and timer accuracy before the timeout begins. The reset timeout of the LTC2909 may be configured in one of three ways: internal 200ms, programmed by external capacitor and no timeout (comparator mode). The mode of the timer is determined by the connection of the TMR pin. + RP4 – 0.5V ADJ2 Setting the Reset Timeout – ADJ2 – VCC Monitoring/UVLO For monitoring a negative supply with a given RN4: RN5 = RN4 + + – 2909 F03 Figure 3. Setting UV and OV Trip Point for a Positive Supply In externally-controlled mode, the TMR pin is connected by a capacitor to ground. The value of that capacitor allows for selection of a timeout ranging from about 400μs to 10 seconds. See the following section for details. 2909fa 12 LTC2909 U W U U APPLICATIO S I FOR ATIO Table 3. Suggested Resistor Values for 5% Monitoring 5% UV NOMINAL RX1 VOLTAGE 24 232k 15 115k 12 49.9k 9 115k 5 137k 3.3 221k 2.5 115k 1.8 63.4k 1.5 59.0k 1.2 127k 1 200k –5 133k –9 97.6k –12 107k –15 107k Trip points are nominal voltage ±6.5%. 5% OV RX2 RX1 RX2 RX4 5% UV and OV RX5 10.2M 3.09M 1.07M 1.82M 1.15M 1.15M 422k 150k 107k 158k 174k 1.37M 1.74M 2.49M 3.09M 102k 200k 102k 78.7k 137k 340k 51.1k 115k 137k 102k 100k 118k 115k 40.2k 309k 5.11M 6.19M 2.49M 1.43M 1.33M 2.05M 221k 324k 301k 158k 113k 1.37M 2.32M 1.07M 10.2M 82.5k 76.8k 76.8k 162k 76.8k 76.8k 137k 82.5k 76.8k 187k 107k 174k 182k 40.2k 309k 11.5k 10.7k 10.7k 22.6k 10.7k 10.7k 19.1k 11.5k 10.7k 26.1k 15.0k 20.0k 22.6k 5.11k 40.2k RX6 4.12M 2.37M 1.87M 2.94M 732k 453k 576k 221k 158k 267k 105k 2.00M 3.65M 1.07M 10.2M If the user wishes to avoid having an external capacitor, the TMR pin should be tied to ground, switching the part to an internal 200ms timer. the threshold is 500mV when the input is below 500mV, and switches to 496.5mV when the input goes above 500mV. If the user requires a shorter timeout than 400μs, or wishes to perform application-specific processing of the reset output, the part may be put in comparator mode by tying the TMR pin to VCC. In comparator mode, the timer is bypassed and comparator outputs go straight to the reset output. The comparator mode feature should be enabled by directly shorting the TMR pin to the VCC pin. Connecting the pin to any other voltage may have unpredictable results. The current required to hold TMR at ground or VCC is about 2μA. To force the pin from the floating state to ground or VCC may require as much as 100μA during the transition. When the part is in comparator mode, one of the two means of preventing false reset has been removed, so a small amount of one-sided hysteresis is added to the inputs to prevent oscillation as the monitored voltage passes through the threshold. This hysteresis is such that the valid-to-invalid transition threshold is unchanged, but the invalid-to-valid threshold is moved by about 0.7%. Thus, when the ADJ input polarity is positive, the threshold voltage is 500mV nominal when the input is above 500mV. As soon as the input drops below 500mV, the threshold moves up to 503.5mV nominal. Conversely, when configured as a negative-polarity input, Selecting the Reset Timing Capacitor Connecting a capacitor, CTMR, between the TMR pin and ground sets the reset timeout, tRST. The following formula approximates the value of capacitor needed for a particular timeout: CTMR = t⎯R⎯S⎯T • 110 [pF/ms] Leaving the TMR pin open with no external capacitor generates a reset timeout of approximately 400μs. Maximum length of the reset timeout is limited by the ability of the part to charge a large capacitor on start-up. Initially, with a large (discharged) capacitor on the TMR pin, the part will assume it is in internal timer mode (since the pin voltage will be at ground). If the 2μA flowing out of the TMR pin does not charge the capacitor to the groundsense threshold within the first 200ms after supplies become good, the internal timer cycle will complete and ⎯R⎯S⎯T will go high too soon. 2909fa 13 LTC2909 U U W U APPLICATIO S I FOR ATIO This imposes a practical limit of 1μF (9 second timeout) if the length of timeout during power-up needs to be longer than 200ms. If the power-up timeout is not important, larger capacitors may be used, subject to the limitation that the capacitor leakage current must not exceed 500nA, or the function of the timer will be impaired. pulled above VCC, providing the voltage limits of the pin are observed. ⎯R⎯S⎯T Output Characteristics The open-drain nature of the ⎯R⎯S⎯T pin allows for wired-OR connection of several LTC2909s to monitor more than two supplies (see Typical Applications). Other logic with opendrain outputs may also connect to the ⎯R⎯S⎯T line, allowing other logic-determined conditions to issue a reset. The DC characteristics of the ⎯R⎯S⎯T pull-down strength are shown in the Typical Performance Characteristics section. ⎯R⎯S⎯T is an open-drain pin and thus requires an external pull-up resistor to the logic supply. ⎯R⎯S⎯T may be As noted in the discussion of power up and power down, the circuits that drive ⎯R⎯S⎯T are powered by VCC. During a fault condition, VCC of at least 0.5V guarantees a VOL of 0.15V at ⎯R⎯S⎯T . U TYPICAL APPLICATIO S Six Supply Undervoltage Monitor with 2.5V Reset Output and 20ms Timeout 15V 5V –5V –15V 3.3V 2.5V SYSTEM CBYP1 100nF RN2A 1.37M VCC ADJ1 RN2B 3.09M CBYP2 100nF RPU 10k RN1A 133k RP2A 1.15M VCC RST RST LTC2909-2.5 ADJ1 RP1A 137k LTC2909-3.3 REF SEL SEL REF ADJ2 TMR TMR ADJ2 RN1B 107k RP2B 3.09M RP1B 115k CTMR1 CTMR2 2.2nF 2.2nF GND 2909 TA02 GND 48V Telecom UV/OV Monitor with Hysteresis VIN 36V TO 72V RP2A 1.43M RCC 27k 0.25W RP2B 1.91M RP2A2 169k 10k* LTC2909-2.5 RP1B 13.7k MANUAL RESET PUSHBUTTON SEL ADJ2 RP1A 18.7k RP1B2 681k REF M1 RN2 2.49M GND RP2 1.07M RN1 107k –12V *OPTIONAL FOR ESD RPU 10k VCC RST ADJ1 RP1 49.9k TMR 2909 TA03 M1, M2: FDG6301N OR SIMILAR 1.8V RST ADJ1 VUV(RISING): 43.3V VUV(FALLING): 38.7V 12V RPU 10k VCC CBYP 100nF RCC 10k 5V M2 VOV(RISING): 71.6V VOV(FALLING): 70.2V ±12V UV Monitor Powered from 12V, 20ms Timeout (1.8V Logic Out) SYSTEM CBYP 100nF FAULT OUTPUT LTC2909-2.5 SEL REF ADJ2 TMR CTMR 2.2nF GND 2909 TA01b IF LOADING OF RST WILL EXCEED 1nF, A 1nF BYPASS CAPACITOR ON M1’s DRAIN IS RECOMMENDED 2909fa 14 LTC2909 U PACKAGE DESCRIPTIO DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702) 0.61 ±0.05 (2 SIDES) R = 0.115 TYP 5 0.56 ± 0.05 (2 SIDES) 3.00 ±0.10 (2 SIDES) 0.675 ±0.05 2.50 ±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 4 0.25 ± 0.05 0.75 ±0.05 0.200 REF 0.50 BSC 2.20 ±0.05 (2 SIDES) 0.38 ± 0.10 8 (DDB8) DFN 1103 0.50 BSC 2.15 ±0.05 (2 SIDES) 0 – 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 1 PIN 1 CHAMFER OF EXPOSED PAD 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 0.09 – 0.20 (NOTE 3) 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 1.95 BSC TS8 TSOT-23 0802 2909fa 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 LTC2909 U TYPICAL APPLICATIO Automotive Supply System with Overvoltage, Overcurrent and Overtemperature Protection and Undervoltage Reset DC/DC D1: 1N5238B OR SIMILAR Q1, Q2: FFB2227 OR SIMILAR VIN 12V DC/DC M1 IRLZ34 RS 0.01Ω RG2 10Ω 2N6507 3.3V SYSTEM CBYP3 100nF RL1 4.7k RCC 4.7k Q1 RP2A 2.49M RP2B 2.05M RP2C 221k RL2 100k RG1 1k RPU1 4.7k CBYP2 100nF VCC ADJ1 RST CG 10nF PWRGD LT1641-2 GND TIMER RP2E 1.15M LTC2909-2.5 RFB2 100k VCC ADJ1 LTC2909-2.5 REF SEL VCC RST ADJ1 RREF 10.7k ON FB TMR CT 680nF CIRCUIT BREAKER AND CROWBAR TMR ADJ2 GND RFB1 10k RP1A 102k RP1B 340k RP1D 49.9k REF SEL SENSE GATE VCC RP2D 1.07M Q2 D1 CBYP1 100nF 2.5V ADJ2 GND RP1C 51.1k NTC THERMISTOR NTHS-1206N01 R25 = 100k R = 10.7k AT 85°C SEL RPU2 10k LTC2909-2.5 RST REF TMR ADJ2 RP1E 221k GND 2909 TA05 12V OV AND 3.3V OV DETECT 2.5V OV AND T > 85°C DETECT 12V, 3.3V and 2.5V UV DETECT RELATED PARTS PART NUMBER DESCRIPTION COMMENTS 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%) LTC1536 Precision Triple Supply Monitor for PCI Applications Meets PCI tFAIL Timing Specifications LTC1540 Nanopower Comparator with Reference Adjustable Hysteresis LTC1726-2.5/LTC1726-5 Micropower Triple Supply Monitor for 2.5V/5V, 3.3V and ADJ Adjustable Reset and Watchdog Time-Outs LTC1727/LTC1728 Micropower Triple Supply Monitor with Open-Drain Reset Individual Monitor Outputs in MSOP/5-Lead SOT-23 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 3mm × 3mm 10-Lead DFN Package 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, Margining Functions LTC2903 Precision Quad Supply Monitor 6-Lead SOT-23 Package, Ultralow Voltage Reset LTC2904/LTC2905 3-State Programmable Precision Dual Supply Monitor LTC2906/LTC2907 Precision Dual Supply Monitor 1-Selectable and 1 Adjustable Adjustable Tolerance and Reset Timer, 8-Lead SOT-23 Package ⎯ S ⎯ T⎯ Outputs/Adjustable Reset Timer Separate VCC Pin, RST/R LTC2908 Precision Six Supply Monitor (Four Fixed and 2 Adjustable) 8-Lead SOT-23 and DDB Packages LT6700 Micropower, Low Voltage, Dual Comparator with 400mV Reference 6-Lead SOT-23 Package 2909fa 16 Linear Technology Corporation LT 0606 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005