rem re MAKI Integrated uP Supervisor Module with Lithium Backup Battery General Description Features The MAX1691 reduces the complexity and number of Internal 3V, 125mAh Lithium Battery components required for power-supply monitoring and , battery contrel functions in microprocessor (uP) sys- 200ms Power OK / Reset Time Delay tems. The MAX1691 features switchover to internal 1A Standby Current, 351A Operating Current backup battery, write protection of CMOS RAM or EEPROM, and a watchdog function. On-Board Gating of Chip-Enable Signals, The internal +3V, 125mAh lithium battery connects to 10ns Max Delay the WP supervisory circuit through external pin strap- # Voltage Monitor for Power-Fail or ping, minimizing battery drain during shipping. Low-Battery Warning The MAX1691 is shipped in special nonconductive 16-Pin, 0.6" Plastic DIP Module material. Note: Storing the MAX1691 in conductive , foam will discharge the internal battery. Applications Ordering Information Computers PART TEMP. RANGE PIN-PACKAGE Control ic 0.6" omroners MAX1691CHE 0% to +70 ht Fiaslc 0.6" Wide Intelligent Instruments oaule Automotive Systems Critical uP Power Monitoring Typical Operating Circuit Pin Configuration +N TOP VIEW FEGULATGR FOR LOADS > 250mA +8 ese.) tL | 3 BATTIN [4 | 18] GATT OUT a of - ws an aI i) Er vi ____ 1 i ec [3] amaxLan fl "EST GND [4] MAXfeg? ~ fis] CEIN BATTIN CEQUT aE BATT ON AAAXLAA _ [5 ha COUT pri MAXteg? SEIN OSCN | 6 | a) Toscin wD) oscse. [7 | Ho] COWLINE NO_7 a2 pe Nu Pri[e 9] PFO CONNECTION _] OSC SEL PFO a NMI [s| [3 | = FESET MYRESET 0.6" Wide DIP Module LOW LINE CNB uP 4 SYSTEM sans 4L INDICATORS - MAXIAA Maxim integrated Products 1 Call toll free 7-800-998-8800 for free samples or literature. L69LXVNMAX1691 Integrated uP Supervisor Module with Lithium Backup Battery ABSOLUTE MAXIMUM RATINGS Terminal Voltage (with respect to GN ND) Voc... All Other Inputs {Note 4)... Input Current BATT OUT ........cceeeeeeeeereees tees we OMA to -25mA .10.3 to +6V 0.3V to (Voyr + 0.30) Voy Peak oo. cccccccecsceecscesseesssaeesseteaeenerseesenerssenseaeeee 1.04 Voo Continuous - 250mA BATT IN Peak 250mA BATT IN Continuous.... 25mA All Other Cutpults ..... Continuous Power Dissipation Plastic DIP Module (derate 8. vomWc) Operating Temperature Range.......... Storage Temperature Range... Lead Temperature (soldering, 10sec) Note 1: The input voltage limits on PFI and WDI may be exceeded if the current into these pins is less than 10mA. Stresses beyond those lisied under Absolute Maximum Ratings may cause permanent damage to the device. These are siress ratings only, and funciional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure ito absolute maximum rating conditions jor exiended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (Voc = 4.75 to 5.5V, VBATTIN = 2.8V applied externally, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Voltage Range, Vcc 0 5.0 5.5 Vv louT = 25mA Voo-0.05 Voc-0.02 Output Voltage, VOUT Voc = 4.5V lour = B50mA Voo.03 Voo.02 Vv Voc to OUT On-Resistance Voc = 4.5V 0.8 1.2 2 Vout in Battery-Backup Mode Voc < VBATT. louT = 100HA VBATT IN - 0.25 Vv Se ees oun) | Yoo> Year 100 | A i | TA = +25C 0.04 1 Moke Exclales lou (Note 2) Voc > VBATTIN- 1.2V Ta = TMIN to TMAX 5 HA VBATT IN Standby Current (Note 3) | VBATT IN+ 0.2V< Voc TAs +25C ot 0.02 HA Ta = TMIN to TMAX -1.0 0.02 Battery-Switchover Threshald Power-up VBATTIN + 0.08 V Power-down VBATT IN - 0.03 Battery-Switchover Hysteresis 60 mv BATT ON Quiput Low Voltage IgnNK = 3.2mA 0.4 Vv BATT GN Output Sink current 60 mA Short-Circuit Current Source current 1 15 100 HA Battery Gapacity (Note 4) 125 mAh Internal Battery Voltage (Note 4) 2.9 Vv RESET AND WATCHDOG TIMER Reset Threshold Voltage 450 4.65 475 Vv Reset Threshold Hysteresis 15 mV Vec to RESET Delay Power-down 80 HS LOWTLINE to RESET Delay 800 ns Feset tee Lumeout Period, Power-up 140 200 280 ms MAAXLMAIntegrated uP Supervisor Module with Lithium Backup Battery ELECTRICAL CHARACTERISTICS (continued) (Voc = 4.75 to 5.5V, VBaTT IN = 2.8V applied externally, Ta = Twin to Tax. unless otherwise noted. Typical values are at +25C.) PARAMETER CONDITIONS MIN TYP MAX | UNITS Reset Active Timeout Period, Extemal Clock | Power-up 2048 Clock Cycles Watchdog Timeout Period, Long period 1.00 1.60 2.25 sec Internal Qscillator Short period 70 100 140 ms Watchdog Timeout Period, Long period 4096 Clock External Clock Short period 1024 Cycles Minimum Watchdog Input Pulse Width VIL = 0.8V, (VIH = 0.75) (Voc) 100 ns I@NK = 5OUA, Voc = 1, VBATTIN = OV, Voc falling 0.004 0.300 RESET Output Voltage ISINK = 3.2mA, Vcc = 4.25V 0.1 0.4 Vv ISQURCE = 1.6mA, Voc = 5 3.5 ___ , Output sink current 60 RESET Gutput Short-Circuit Gurrent mA Qutput source current 7 20 RESET Output Voltage Low (Note 5) ISINK = 3.2mA 0.1 0.4 V RESET Output Short-Circuit Current (Note 5) | Gutput sink current 60 mA a | = 3.2mA, Voc = 4.25V o4 LOWTLINE Output Voltage SINK oe v ISOURCE = 1p, Voc = 5V 35 oo. Qutput sink current 60 mA LOW LINE Output Short-Circuit Current Output source current 1 15 100 pA VIH 0.75 x Voc WDI Threshold Voltage (Note 6) Vv VIL 0.8 WDI = oV -50 -10 WDI Input Current pA WDI = Vout 20 50 POWER-FAIL COMPARATOR PFI Input Threshold Voo = 5V 1.20 1.25 1.30 V PFI Leakage Current +0.01 25 nA - ISINK = 3.2mA 0.4 PRO Output Voltage Vv p 9 ISOURCE = 1p, Voc = 5V 35 , Output sink current 60 mA PFO Output Short-Circuit Current Output source current 1 15 100 pA Vin = -20mV, Vop = 15mV 25 PFI to PFO Delay IN op ps Vin = 20m, Vop = 15mV 60 CHIP-ENABLE GATING CE IN Leakage Current Disabled mode +0.005 +1 pA CE IN to CE OUT Resistance (Note 7) Enabled mode 75 150 3 CE OUT Short-Circuit Current {Reset Active) Disabled mode, CE OUT = 0V 0.10 0.75 2.00 mA CE IN to CE OUT Propagation Delay (Note 8) | 502 source impedance driver, CLoaD = 50pF 6 10 ns CE OUT Output Voltage High Voc = 5, louT = -100nA 3.5 V (Reset Active) Voc = OV, VBATTIN = 2.8V, lout = 1HA 27 RESET to CE OUT Delay Power-down 12 us MA AXILAA 3 L69LXVNMAX1691 Integrated uP Supervisor Module with Lithium Backup Battery ELECTRICAL CHARACTERISTICS (continued) (Voc = 4.754 to 5.5V, VeaTT IN = 2.8V applied externally, Ta = Twin to Tax. unless otherwise noted. Typical values are at 25C.) PARAMETER | CONDITIONS [| MIN TYP MAX | UNITS | INTERNAL OSCILLATOR OSC IN Leakage Current OSC SEL = 0V 0.10 45 pA OSC IN Input Pull-Up Current OSC SEL = Vout or floating, GSC IN = 0V 10 100 pA OSC SEL Input Pull-Up Current OSC SEL = 0V 10 100 pA O8& IN Frequency Range OSC SEL = 0V 50 kHz OSC IN Frequency with External Capacitor OSC SEL = OV, Cosc = 47pF 100 kHz Note 2: The supply current drawn from the battery excluding louT typically goes to 18WA when (VBATTIN - 1) < Yoo < VBATTIN. In most applications, this is a brief period as Vcc falls through this region. Note 3: "+" = battery-discharging current, "= battery-charging current. Note 4: See Typical Operating Characteristics. Note 5: RESET is an open-drain output and sinks current only. Note 6: WDI is internally connected to a voltage divider between VouT and GND. If unconnected, WDI is driven to 1.6 (typ), disabling the watchdog function. Note 7: The chip-enable resistance is tested with Voc = 4.75V. VCE IN = VGE OUT= Voc /2. Note 8: The chip-enable propagation delay is measured from the 50% point at CE IN to the 50% point at CE OUT. Typical Operating Characteristics (VBATT IN = 2.8V externally applied, Voc = 5.0V, Ta = +25C, unless otherwise noted .) Vee SUPPLY CURRENT BATT IN SUPPLY CURRENT vs. TEMPERATURE vs. TEM PERATURE CHI|P-ENABLE ON-RESISTANCE (NORM AL OPERATING M CDE) (BATTERY -BACKUP MQDE) vs. TEMPERATURE 50 - . 120 * PAL, CEIN = ov 3 Yoo = v, 3 _ Veg = 4 75V, 2 _ ig NO LOAD 8 Vee n= Veo! 2 2 gs 5 2 100 c a = a = f 3 a gery S 4p * = 80 Leer > fa So Lanner] 4 oa uu Laveseeeerntnen) & a a aso = > =< aq Pl ir a 50 2 3 E a Pet = = Pe a S 30 40 o 10 20 30 40 50 60 70 o 10 2 30 40 50 BO O70 o 10 20 30 40 50 680 70 TEMPERATURE {C} TEMPERATURE {C| TEMPERATURE (C 4 PRAXKLAAIntegrated uP Supervisor Module with Lithium Backup Battery (VBATT IN = 2.8V externally applied, Voc = Veatt in TO OUT ON- RESISTANCE vs, TEM PERATURE 20 Voo= 0 Crory] BATT IN TO QUT ON-RESI STANCE (2) oO 100620068006 6400 BOD TEMPERATURE (C) RESET THRESHCLD vs, TEMPERATURE 475 MAneat 7 470 } a a mH 460 455 450 445 440 RESET THRESHOLD ( 435 430 oO 10062006800 6400 50D TEMPERATURE (C) BATT IN CURRENT vs. INPUT SUPPLY VOLTAGE PAAAIEML 101 lgut= 0A |BATT IN (HA) 5.0V, Ta = +25C, unless otherwise noted.) Vcc TO OUT ON-RESISTANCE vs. TEM PERATURE og 08 Voc TO OUT ON-RESISTANCE () OF 06 oO 10 0620068006400 6807 TEMPERATURE {C} RESET QUTPUT RESISTANCE vs. TEMPERATURE 600 MANIGRL a 500 4p |. SOURCING CURRENT 300 200 Voo= OV, SINKING CURRENT RESET OUTPUT RESISTANCE (2) 100 Q Oo 610062006 680 40 GO TEMPERATURE (C) WATCHDOG AND RESET TIMEOUT PERIOD vs. OSC IN TIMING CAPACITOR (Cogc) 100 = zs z LONG WATCHODG = TIMEGUT PERI OD B 10 oa o & oa bE a 9 4 = SHORT WATCHODG RESET ACTIVE TIMECUT PERIOD TIMEOUT PERIOD 0 10 100 1000 Case (pF) ho un mR o a S o wn o o he 7 RESET DELAY (ms} PROPAGATION DELAY (ns) PA THRESHOLD (} 3 20 Typical Operating Characteristics (continued) PFI THRESHOLD vs, TEMPERATURE aan 6a1 8 L69LXVN 10 200 630064006 6-80 TEMPERATURE (*C} RESET DELAY vs, TEMPERATURE MAKES! Von= OV TOBY Oo 61006200 630) C40 CPD TEMPERATURE {C} CHIP- ENABLE PROPAGATION DELAY vs, CE OUT LOAD CAPACITANCE | PAANIEL 12 YL | Vee n= OV TOBY DRIVER SOURCE IMPEDANCE = 500 a 50 100 150 200 250 Loan {PF}MAX1691 Integrated uP Supervisor Module with Lithium Backup Battery Typical Operating Characteristics (continued) (VBATT IN = 2.8V externally applied, Voc = 5.0V, Ta = +25C, unless otherwise noted.) Vcc TO Vout vs. OUTPUT CURRENT BATT IN TO Vout vs. CUTPUT CURRENT _ (NORMAL OP ERATING MCLE) (BATTERY-BACKUP MCDE) Voc TOLOW LINE AND CE QUT DELAY 1000 * 1000 : 3 z 3 z +5 Voc RESET = THRSHOLD = 100 tee tao = 100 SLOPE = 80 4 = 5 LOW LINE 5 5 LO 2 Re 2 z Hl g E 7 AESET S LO _ Hi Vop=4 5 CE OUT =0V 1 1 LO 1 10 100 1000 1 10 100 lout {mA} lout (mA) Typical Battery Characteristics* (Note 9} EFFECT OF LOAD RESISTANCE LOAD CHARACTERISTICS TEMPERATURE CHARACTERISTICS ON OP ERATING VOLTAGE 35 2 = 42 2 Ta= 420C Jo LOAD 15k [8 a 3 g Lr Z 30 Ta = 480C Es Lee a Ler] Lata = f mh r Ler = a5 Ss = Let ly w an 3 28 Lt LU = o a =| f Si eo TT = 15ko | 30k | 50KO > Ta=-10C | Ty = 420C B28 OH wh = N NO Wita = +9086 214074) 15 2 24 pt Ta = 420C (+68F) 5 NIN Ta= 10C (414F) = PN Ta = -20C (-4F] 10 ean 0 1000 2000 3000 4000 5000 6000 0 6200 400s BDDsSs=(iODS1DG ot 1 10 SERVICE LIFE (Hrs) SEAVICE LIFE {Hrs} LOAD (M2) *Source: Rayovac Note 9: Nominal voltage is 3.0V, nominal capacity is 130mAh at 30kQ to 2.0V at +21 C. Typical storage life is less than 0.5% per year at +21 C. Operating temperature range is -40C to +70C; prolonged operation and/or storage at elevated termpera- tures affects life and reliability. 6 MRAAXLAAIntegrated uP Supervisor Module with Lithium Backup Battery Pin Description PIN NAME FUNCTION 1 BATT IN Backup-battery input. Gonnect to BATT GUT. Output supply voltage connects to Vcc when Vcc is greater than VBATTIN and above the reset 2 OUT threshold. When Vec falls below VgaTTIN and is below the reset threshold, OUT connects to BATT IN. Connect a 0.1pF capacitor from OUT to GND. 3 Voc Input supply voltage, +5 input. 4 GND Ground. OV reference for all signals. Connected to the negative terminal of the internal battery. 5 BATT ON Battery-on output goes high when OUT switches to BATT IN. BATT ON goes low when OUT switches to Voc. Connect the base of a PNP to BATT ON for QUT current requirements greater than 250mA. External oscillator input . When OSC SEL is unconnected or driven high, the internal oscillator sets the 6 OSC IN reset delay and watchdog timeout period. The timing can be adjusted by connecting an external capacitor to this pin (Figure 2). When OSC SEL is high or floating, OSC IN selects between fast and slow watchdog timeout periods. Oscillator select. When OSC SEL is unconnected or driven high, the intemal oscillator sets the reset 7 OSC SEL delay and the watchdog timeout period. Setting OSC SEL low enables OSC IN {Table 1}. OSC SEL has a 10HA intemal pull-up. a PFI Power-fail input is the noninverting input to the power-fail comparator. When PFI is less than 1.25, PFG goes low. Connect PFI to GND or OUT when not used. 9 PFO Power-fail output is the output of the power-fail comparator. PFO goes low when PFI is less than 1.25V. PFOis an uncommitted comparator, and has no effect on any other internal circuitry. maae | LOW LINE output goes low when Vcc falls below the reset threshold. It returns high as soon as Vcc 10 LOW LINE ; rises above the reset threshold. Watchdog inputa three level input. If WDI remains either high or low for longer than the watchdog 14 WO! timeout period, reset is asserted. Leaving WDI unconnected disables the watchdog function. WDI connects to an intemal voltage divider between QUT and GND that sets it to mid-supply when lett unconnected. Chip-enable output goes low only when CE IN is low and Vcc is above the reset threshold. If CE IN is 12 CEOUT low when reset is asserted, CE OUT will stay low for 12p1s or until CE IN goes high, whichever occurs first. 13 CE IN Chip-enable input to CE gating circuit. Connect to GND or QUT if not used. scec RESET output goes low whenever Vcc falls below the reset threshold. RESET remains low typically for 14 RESET 200ms after Vcc crosses the reset threshold on power-up. 15 RESET Active-high reset output is open drain and the inverse of RESET. 16 BATT OUT Battery output connects to the positive terminal of the internal 125mAh lithium battery. Gonnect BATT OUT to BATT IN. MAAXLAA L69LXVNMAX1691 Integrated uP Supervisor Module with Lithium Backup Battery Detailed Description The MAX1691 combines a MAX691A integrated circuit and a 125mAh battery in one package. All pins on the MAX691A are available on the MAX1691 except WDO. The MAX1691 is not pin compatible with the MAX691A. RESET and RESET Outputs The MAX1691's RESET and RESET outputs ensure the uP (with reset inputs either asserted high or low) pow- ers up in a Known state and prevent code execution errors during power-down or brownout conditions. The active-low RESET output both sources and sinks current, while the open-drain RESET output sinks current only. For a battery voltage > 2V, RESET and RESET remain valid for Voc from OV to 5.5V. RESET and RESETare asserted when Vcc falls below the 4.65V reset threshold and typically remain asserted for 200ms after Vcc rises above the reset threshold on power-up (Figure 1). The MAX1691 battery switchover compara- tor does not affect reset assertion. However, both reset outputs are asserted in battery-backup mode since Vcc must be below the reset threshold to enter battery- backup mode. Watchdog Function The watchdog monitors uP activity via the watchdog input (WDI). If the pP becomes inactive, RESET and RESET are asserted. To use the watchdog function, con- nect WDI to a bus line or pP input/output (I/O) line. If WDI remains high or low for longer than the watchdog timeout period (1.6sec nominal), RESET and RESET are asserted (see AESET and RESET Outpuis section). WD! Watchdog Input Changing WDI's state (high-to-low, low-to-high, or a minimum 100ns pulse) during the watchdog period resets the watchdog timer. The watchdog timer default pericd is 1.6sec. Disable the watchdog function by floating WDI. An internal resistor network (100k equivalent impedance at WDI) biases WDI to approximately 1.6V. Internal comparators detect this level and disable the watch- dog timer. When Vcc is below the reset threshold, the watchdog function is disabled and WDI is disconnect- ed from its internal resistor network, thus becoming high impedance. Selecting Alternative Watchdog and Reset Timeout Periods The OSC SEL and OSC IN inputs control the watchdog and reset timeout periods. Floating OSC SEL and OSC IN or tying them both to GUT selects the nominal 1.6sec watchdog timeout period and 200ms reset time- out period. Connecting OSC IN to GND and floating or 5W RESET 4q THRESHOLD 5 CEIN ww wv Ov LOGIC LEVELS SHOWN ARE FROM OV TOSY | Figure f. Reset and Chip-Enable Timing 3 PRAXKLAAIntegrated uP Supervisor Module with Lithium Backup Battery WO | fo AEBET pa 12 | vee BES +1 = RESET TIMEOUT PERCD te = NORM AL WATCHDOG TIMEQUT PERIOD tg = WATCHDOG TIMEOUT PERCD IMMEDIATELY AFTER RESET MAXIM MAXI691 EXTERNAL EXTERNAL CLOCK OSCILLATOR 8 8 ses Eo csc SEL 7 7 BOkHZ OSC IN p YSciN INTERNAL OSCILLATOR INTERNAL OSCILLATOR 18sec WATCHDOG to0ms WATCHDOG NC 84 ogc se. NC 8] ogc se. NC Alose in oT CSCIN Figure 2. Watchdog Timeout Period and Reset Active Time Figure 3. Oscifiator Circuits Table 1. Reset Pulse Width and Watchdog Timeout Selections OSc SEL OSC IN Watchdog Timeout Period Reset Timeout Normal Immediately After Reset Period Low External clock input 1-24 clks 4096 clks 2048 clks Low External capacitor (600/47pF x C)ms (2.4/47pF x C)sec (1200/47pF x C)ms Floating Low 100ms 1.6sec 200ms Floating Floating 1.6560 1.6sec 200ms connecting OSG SEL to OUT selects the 100ms normal GE IN Chip-Enable input watchdog timeout delay and 1.6sec delay immediately after reset. The reset timeout delay remains 200ms (Figure 2). Select alternative timeout periods by con- necting GSC SEL to GND and a capacitor between O8C IN and GND or externally driving OSC IN (see Table 1 and Figure 3). Chip-Enable Signal Gating The MAX1691 provides internal gating of chip-enable sig- nals to prevent erroneous data from being written to CMOS RAM in case of power failure. During nonmal oper- ation, the chip-enable gate is enabled and passes all chip-enable (CE) transitions. When reset is asserted, this path becomes disabled, preventing erroneous data from corrupting the CMOS RAM. The MAX1691 uses a series transmission gate from CE IN to CE OUT (Figure 4). The 10ns (max) CE propagation delay from CE IN to CE OUT makes the MAX1691 compatible with most LPs (Figure 5 shows the test circuit for CE propagation delay). MAAXLAA CE IN is high impedance (disabled mode) while RESET and RESETare asserted. During a power-down sequence where VCC falls below the reset threshold, or when a watchdog fault occurs, CE IN assumes a high-impedance state when the volt- age at CE IN goes high or 15us after reset is asserted, whichever occurs first (Figure 1). During @ power-up sequence, CE IN remains high impedance regardless of CE IN activity until reset is deasserted following the reset timeout period. In the low-impedance mode, CE IN's impedance appears as a 75Q resistor in series with the load at CE OUT. The propagation delay through the GE transmission gate depends on both the source impedance of the drive to CE IN and the capacitive loading on the chip- enable output (CE OUT) (see Chip-Enable Propagation Delay vs. CE OUT Load Capacitance in the Typical Operaiing Characieristics). The CE propagation delay 9 L69LXVNMAX1691 Integrated uP Supervisor Module with Lithium Backup Battery BATT ON a 5 oN M 0 owe 465 a Veo i 3 = >> - --@------ OUT l | BATT IN-! 3, 125mAh CHP-ENABLE parr out S} ___+| a BATTERY OUTPUT p LL CONTROL cen 8 4 . e 2 mE CuT | # Hye RESET JA AXIS MAXt891 (|e i __ N GENERATOR > 4 CSCIN m2 TIMERASE FOR | ESET - FESET AND OSC SEL te WATCHDOG WATCHDOG WO! pet! TRANSITION allt PA om PN ere LL _* i ND 4 Figure 4. Block Diagram is production tested from the 50% point of CE IN to the 50% point of CE OUT using a 50 driver and 50pF of load capacitance (Figure 5). For minimum propagation delay, minimize the capacitive load at CE OUT and use a low output impedance driver. __Chip-Enabie Output CE OUT In the enabled mode, CE OUTs impedance is equiva- lent to 75Q in series with the source driving CE IN. In the disabled mode, the 758 analog switch is off and CE OUT is pulled to OUT. This source turns off when the analog gate is enabled. 19 __ LOW LINE Output LOW LINE is the buffered output of the reset threshold comparator and is pulled low when Voc is below the reset threshold. For normal operation (Vcc above the reset threshold), LOW LINE is pulled to OUT. Power-Fail Comparator The power-fail comparator is an uncommitted comparator that has no effect on the IC's other functions. Gommon uses include low-battery indication (Figure 6) and early power-fail warning (see Typical Operating Circuih. PRAXKLAAIntegrated uP Supervisor Module with Lithium Backup Battery +5 Veo BATT IN AANAXLAA MAX1E91 BATT OUT 500 OUTPUT CEIN IMPEDANCE CEQUT - +5 | Vee BATT OUT MAAXLAA MAXI697 BATT IN PFO] LOW BATT Q.cap 2 Lt GND t Figure 5. C& Propagation Delay Test Circuit Figure 6. Low-Baitery indicator PF! Power-Fail Input input Supply Voltage PFI is the power-fail comparators input. PFI has a guaranteed maximum input leakage of +25nA over temperature, so the current through the resistive divider connected to PFI should be at least 1A to maintain trip point accuracy. The typical comparator delay is 25us from VIL to VOL, and 7Ous from VIH to VOH. If unused, connect PFI to ground. _____- PFO Power-Fail Output The power-fail output (PFO) goes low when PFI goes below 1.25V. It typically sinks 3.2mA with a 0.1V satu- ration voltage. With PFI above 1.25V, PFO is pulled to QUT with only 1A source capability, so an external pull-up resistor is often required. Baittery-Backup Mode The MAX1691 requires two conditions to switch to bat- tery-backup mode: (1) Vcc must be below the reset threshold, and (2) Vcc must be below VBATT IN. Table 2 lists the status of the inputs and outputs in battery- backup mode. BATT ON Output The battery-on (BATT ON) output indicates the status of the internal Vcc/battery switchover comparator, which in turn controls the internal Vcc and battery switches. For Vcc greater than VBATT IN {ignoring the small hys- teresis effect), BATT ON typically sinks 3.2mA at less than 0.1V saturation voltage. In battery-backup mode, BATT ON is pulled up to OUT. Use BATT ON to indi- cate battery switchover status or to supply base drive to an external PNP pass transistor for higher current applications (see Typical Operating Circuit. MAAXLAA The input supply voltage (Vcc) should be a regulated +5V. Voc connects to OUT through a parallel diode and a large PMOS switch. The switch carries the entire current load for currents less than 250mA. The parallel diode carries any current in excess of 250mA. Both the switch and the diode have impedances less than 12. The maximum continuous current is 250mA, but power- on transients may reach a maximum of 1A without damage (Figure 7). Backup-Battery Input The backup-battery input (BATT IN) is similar to the Vcc input except the PMOS switch and parallel diode are much smaller. Accordingly, the on-resistances of both the diode and the switch are each approximate- ly 108. Continuous current should be limited to 25mA and peak currents (only during power-up) limit- ed to 250mA. The reverse leakage of BATT IN is less than 1pA over temperature and supply voltage. To use the internal 125mAh backup battery, connect BATT IN to BATT OUT. OQuiput Supply Voltage The output supply voltage (OUT) pin internally con- nects to the IC's substrate and supplies current to the external system and internal circuitry. All open-circuit outputs except RESET will, for example, assume VOUT in their high states and not the Voc voltage. At the maximum source current of 250mA, VOUT is typically 200mV below Voc. Decouple this terminal with a 0.1pF capacitor to GND. 11 L69LXVNMAX1691 Integrated uP Supervisor Module with Lithium Backup Battery Table 2. Input and Output Status in Battery-Backup Mode which PFO is inactive. PIN NAME STATUS 1 BATT IN Supply current is 14 maximum. 2 OUT QUT is connected to BATT IN through an internal PMOS switch. 3 Voc Battery switchover comparator monitors Vcc for active switchover. 4 GND GND, OV reference for all signals. 5 BATT ON Logic high. The open-circuit output is equal to VOUT. 6 OSC IN OSG IN is ignored. 7 OSC SEL OSG SEL is ignored. 8 PFI The power -fail comparator remains active in battery-backup mode until Voc < VBATT IN - 1.2V, below which PFI is inactive. 9 PRO The power-fail comparator remains active in battery-backup mode until Vcc < VBATT IN - 1.2V, below 10 LOWLINE Logic low. 11 WDI Watchdog is ignored. 12 CE IN High impedance. 13 CE OUT Logic high. The open-circuit voltage is equal to VOUT. 14 RESET Logic low. 15 RESET High impedance. 16 BATT GUT | Connect BATT GUT to BATT IN. Applications Information The MAX1691 is not short-circuit protected. Shorting OUT te ground will destroy the device. If long leads connect to the chip inputs, ensure these leads are free from ringing and other conditions that would forward bias the chip's protection diodes. Storing the MAX1691 in conductive foam can slowly discharge the internal battery. There are three distinct modes of operation: (1) Normal operating mode with all circuitry powered up. Typical supply current from Voc is 35yA while only leakage currents (< 1A) flow from the battery. (2) Battery-backup mode where Vcc is typically within 1.2V below VBATT IN. All circuitry is powered up and the supply current from the battery is typically less than 60LA. (3) Battery-backup mode where Vec is less than VBATT IN by atleast 1.2V. BATT IN supply current is 1A max. Alternative CE Gating Using memory devices with both CE and CE inputs allows the CE loop to be bypassed. To do this, con- 12 nect CE IN to ground, pull up CE OUT to OUT and con- nect CE OUT to the CE input of each memory device as in Figure 8. The CE input of each part then connects directly to the chip select logic, which then does not have to be gated. ee BATTIN . MAAXLAM MAXI691 eer tee OUT 0 4p1F IH Le Figure 7. Voc and BATT IN to OUT Switch PRAXKLAAIntegrated uP Supervisor Module with Lithium Backup Battery Ay = pv * cE PAM OUT cE CEIN CECUT ae @ ce ~ MAAXLAA PAM? MAX1691 cE ec RAMS ND cE tL CE RAMA [| CE * MAXIMUM Rp VALUEDEPENDS a ON THE NUM BER CF RAMS, ACTIVE HIGH CELINES MINIMUM Rip VALUES 1k02 FROM LOGC. Voc PA MAAXLAA MAX1697 PFO a = oO IH = Topp +54 PRO ov l T ov vi vi L Vigp *t * OPTIONAL Vin Pell Bs ) Rt A8 Re Vi=1 26 eer Figure 8. Atemate CE Gating Adding Hysteresis to the Power-Fail Comparator Hysteresis adds a noise margin to the power-fail com- parator and prevents repeated triggering of PRO when VIN is near the power-fail comparator trip point. Figure 9 shows how to add hysteresis to the power-fail com- parator. Select the ratio of Rl and R2 such that PFI sees 1.25V when VIN falls to the desired trip point (VTRIP). Resistor R3 adds hysteresis. It will typically be an order of magnitude greater than Ri or R2. The cur- rent through R1 and R2 should be at least 1A to ensure the 25nA (max) PFI input current does not shift the trip point. R3 should be larger than 10k to pre- vent it from loading down the PFOpin. Capacitor C1 is optional and adds additional noise rejection. Monitoring a Negative Voltage The power-fail comparator can be used to monitor a negative supply voltage using Figure 10s circuit. PFO is low when the negative supply is valid. PROgoes high when the negative supply voltage droops. This circuit's accuracy is affected by variations in the PFI threshold, the Voc voltage, and resistors R1 and R2. MAAXLAA Figure 9. Adding Hysteresis to the Power-Fail Gomparator ov Vip ov BV-125V _125V-Vrap RA Re NOTE: Viqp |S NEGATIVE Figure 10. Monitoring a Negative Voliage 13 L69LXVNMAX1691 Integrated uP Supervisor Module with Lithium Backup Battery o oS z \ Voo=5 | | a 3 Tas 425C i 5 a 0 {WF CAPACITOR = N FROM Voyr TOGND! = g N 60 = i i N a Z 40 N oc Ec = Me = hw = 20 Z \ a, D 10 400 1000 10000 RESET COMPARATOR OVERDAIYVE, (Reset Threshold Voltage - Ver) (mV) Figure 17. Maximum Transient Duration without Causing a Aeset Pulse vs. Reset Comparator Overdrive Negative-Going Vcc Transients While issuing resets to the WP during power-up, power- down, and brownout conditions, these supervisors are relatively immune to short-duration, negative-going Vcc transients (glitches). It is usually undesirable to reset the WP when Veg experiences only small glitches. Figure 11 shows maximum transient duration vs. reset- comparator overdrive, for which reset pulses are not generated. The graph was produced using negative- going Voc pulses, starting at 5V and ending below the reset threshold by the magnitude indicated (reset com- parator overdrive). The graph shows the maximum pulse width a negative-going Ver transient may typical- ly have without causing a reset pulse to be issued. As the amplitude of the transient increases (i.e., goes far- ther below the reset threshold), the maximum allowable pulse width decreases. Typically, a Veg transient that goes 100mV below the reset threshold and lasts for 40us or less will not cause a reset pulse to be issued. A 100nF bypass capacitor mounted close to the Vog pin provides additional transient immunity. Connecting a Timing Capacitor at OSC IN When OSC SEL is connected to ground, OSC IN dis- connects from its internal 10uHA (typ) pull-up and is internally connected to a +100nA current source. When a capacitor is connected from OSC IN to ground (to select alternative reset and watchdog timeout peri- ods), the current source charges and discharges the timing capacitor to create the oscillator that controls the reset and watchdog timeout period. To prevent timing errors or oscillator start-up problems, minimize external current leakage sources at this pin, and locate the capacitor as close to OSC IN as possible. The sum of 14 PC board leakage + OSC capacitor leakage must be small compared to +100nA. Maximum Voc Fall Time The Vgc fall time is limited by the propagation delay of the battery switchover comparator and should not exceed 0.03V/us. A standard rule of thumb for filter capacitance on most regulators is on the order of 100UF per amp of current. When the power supply is shut off or the main battery is disconnected, the associated initial Voc fall rate is just the inverse or TA/O0UF = 0.01V/us. The Veg fall rate decreases with time as Veg falls exponentially, which more than satisfies the maximum fall-time requirement. Watchdog Software Considerations A way to help the watchdog timer keep a closer watch on software execution involves setting and resetting the watchdog input at different points in the program, rather than pulsing the watchdog input high-low-high or low-high-low. This technique avoids a stuck loop where the watchdog timer continues to be reset within the loop, keeping the watchdog from timing out. Figure 12 shows an example flow diagram where the I/O dii- ving the watchdog input is set high at the beginning of the program, set low at the beginning of every subrou- tine or loop, then set high again when the program returns to the beginning. If the program should hang in any subroutine, the 1/0 is continually set low and the watchdog timer is allowed to time out, causing a reset or interrupt to be issued. START SET WD! LOW SUBROUTINE OR PROGRAM LOCP SET WD HIGH FETURN Figure 12. Watehdog Flow Diagram PRAXKLAAIntegrated uP Supervisor Module with Lithium Backup Battery Product Selection Guide WITH | MAX791 (Has Low-Line Output) CHIP- ENABLE WATCH poe pe MAXEBIA, MAXGOSA GATING | MAXBOOLIM (42% Power- Fail) witH t |______________ anos, MAX704, MAXTO4RV/S/T | BATTERY-BACKUP varonnoe : , . ([- a SWITCHOVER | MAXGOGRISIT (42% Power-Fail) k WITHOUT RESET |- MAX690A, MAX692A, MAX690R/S/T CHIF- ENABLE ACTIVE LOW GATING | | MAXBO2L/M/RISIT (42% Power-Fail) k WITH WATCHDOG | RESET | MAXBOSL/RIS/T ACTIVE HIGH = | MAXBO4RISIT (42% Power-Fail) WITH RESET ane ENABLE MAXTO2L/M/RISIT GATING MAXB20L/M/RISIT (42% Power-Fail) | WITHOUT WITHOUT | __________________ Wax707, MAX708, MAX70BRISIT BATTERY-BACKUP WATCHDOG MAKTO => SWITCHOVER MAX7O9L/M/RISIT (RESET ONLY) WITHOUT : RESET CHIP-ENABLE [ MAX705, MAXTO6, MAXTOSRISIT ACTIVE LOW GATING , k WITH WATCHDOG | RESET AGTIVEHIGH | 7Pr MAXTOBP, MAXB13L MA AXILAA 15 L69LXVNMAX1691 Integrated uP Supervisor Module with Lithium Backup Battery Package Information INCHES MILLIMETERS DIM MIN MAX MIN MAX A = 0.375 = 9.53 B | 0.014 | 0.026 0.36 0.66 Cc | 0.008 | 0.018 0.20 046 D = 0.875 = 22.23 E |0.700 | 0.725 | 17.78 18.42 e 0.600 BSC 15.24 BSC en 0.100 BSC 2.54 BSC L | 0.120 | 0.200 3.05 5.08 21-0038B 16-PIN PLASTIC DUAL-IN-LINE MODULE (0.600 in.) , \_ | Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit paient licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice ai any time. 16 Maxim Infegrated Products, 120 San Gabrie! Drive, Sunnyvale, CA 94086 (408) 737-7600 1995 Maxim Integrated Products Printed USA MAXIM. is a registered trademark of Maxim Integrated Products.