19-4333; Rev 3; 9/93 Microprocessor Supervisory Circuits _______________________Applications Battery-Powered Computers and Controllers Intelligent Instruments Automotive Systems Critical µP Power Monitoring ___________________________Features ♦ Precision Supply-Voltage Monitor: 4.65V for MAX690A/MAX802L/MAX805L 4.40V for MAX692A/MAX802M ♦ Reset Time Delay – 200ms ♦ Watchdog Timer – 1.6sec Timeout ♦ Battery-Backup Power Switching ♦ 200µA Quiescent Supply Current ♦ 50nA Quiescent Supply Current in BatteryBackup Mode ♦ Voltage Monitor for Power-Fail or Low-Battery Warning ♦ Power-Fail Accuracy Guaranteed to ±2% (MAX802L/M) ♦ Guaranteed RESET Assertion to VCC = 1V ♦ 8-Pin SO and DIP Packages ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX690ACPA 0°C to +70°C 8 Plastic DIP MAX690ACSA 0°C to +70°C 8 SO MAX690AC/D 0°C to +70°C MAX690AEPA -40°C to +85°C 8 Plastic DIP MAX690AESA -40°C to +85°C 8 SO MAX690AMJA -55°C to +125°C 8 CERDIP** Dice* Ordering Information continued on last page. * Dice are specified at TA = +25°C **Contact factory for availability and processing to MIL-STD-883. _________________Pin Configurations __________Typical Operating Circuit TOP VIEW UNREGULATED DC REGULATED +5V R1 O.1µF VCC VCC PFI R2 PFO WDI VBATT VOUT GND NMI µP I/O LINE GND VCC MAX690A MAX802L V OUT 1 V CC 2 RESET BUS 3.6V LITHIUM BATTERY RESET GND 3 PFI 4 MAX690A MAX692A MAX802L MAX802M MAX805L 8 V BATT 7 RESET (RESET) 6 WDI 5 PFO DIP/SO CMOS RAM GND ( ) ARE FOR MAX805L ONLY. ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX690A/MAX692A/MAX802L/MAX802M/MAX805L __________________General Description The MAX690A/MAX692A/MAX802L/MAX802M/MAX805L reduce the complexity and number of components required for power-supply monitoring and battery-control functions in microprocessor (µP) systems. They significantly improve system reliability and accuracy compared to separate ICs or discrete components. These parts provide four functions: 1) A reset output during power-up, power-down, and brownout conditions. 2) Battery-backup switching for CMOS RAM, CMOS µP, or other low-power logic. 3) A reset pulse if the optional watchdog timer has not been toggled within 1.6sec. 4) A 1.25V threshold detector for power-fail warning or low-battery detection, or to monitor a power supply other than +5V. The parts differ in their reset-voltage threshold levels and reset outputs. The MAX690A/MAX802L/MAX805L generate a reset pulse when the supply voltage drops below 4.65V, and the MAX692A/MAX802M generate a reset below 4.40V. The MAX802L/MAX802M guarantee power-fail accuracies to ±2%. The MAX805L is the same as the MAX690A except that RESET is provided instead of RESET. All parts are available in 8-pin DIP and SO packages. The MAX690A/MAX802L are pin compatible with the MAX690 and MAX694. The MAX692A/MAX802M are pin compatible with the MAX692. MAX690A/MAX692A/MAX802L/MAX802M/MAX805L Microprocessor Supervisory Circuits ABSOLUTE MAXIMUM RATINGS Terminal Voltage (with respect to GND) VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V VBATT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V All Other Inputs (Note 1) . . . . . . . . . . . . . . . . -0.3V to (VCC + 0.3V) Input Current VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200mA VBATT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA Output Current VOUT . . . . . . . . . . . . . . . . . . . Short-Circuit Protected for up to 10sec All Other Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA Rate of Rise, VCC, VBATT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100V/µs Continuous Power Dissipation Plastic DIP (derate 9.09mW/°C above +70°C) . . . . . . . . 727mW SO (derate 5.88mW/°C above +70°C) . . . . . . . . . . . . . . . . 471mW CERDIP (derate 8.00mW/°C above +70°C) . . . . . . . . . . . 640mW Operating Temperature Ranges: MAX69_AC_ _, MAX80_ _ C_ _ . . . . . . . . . . . . . . . . . . 0°C to +70°C MAX69_AE_ _, MAX80_ _ E_ _ . . . . . . . . . . . . . . . . -40°C to +85°C MAX69_AMJA, MAX805LMJA. . . . . . . . . . . . . . . . -55°C to +125°C Storage Temperature Range . . . . . . . . . . . . . . . . . . -65°C to +160°C Lead Temperature (soldering, 10sec) . . . . . . . . . . . . . . . . . . +300°C Note 1: The input voltage limits on PFI and WDI may be exceeded if the current into these pins is limited to less than 10mA. Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V CC = 4.75V to 5.5V for MAX690A/MAX802L/MAX805L, V CC = 4.5V to 5.5V for MAX692A/MAX802M, V BATT = 2.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL Operating Voltage Range, VCC, VBATT (Note 2) Supply Current (Excluding IOUT) ISUPPLY ISUPPLY in Battery-Backup Mode (Excluding IOUT) CONDITIONS MAX69_AC, MAX802_C MIN 1.0 MAX805LC MAX69_AE/M, MAX80_ _E VOUT Output VOUT in Battery-Backup Mode Battery Switch Threshold, VCC to VBATT MAX 5.5 UNITS 1.1 5.5 V 1.2 5.5 MAX69_AC, MAX802_C 200 350 MAX69_AE/M, MAX802_E, MAX805LE/M TA = +25°C VCC = 0V, VBATT = 2.8V TA = TMIN to TMAX 200 500 5.5V > VCC> VBATT +0.2V VBATT Standby Current (Note 3) TA = +25°C TA = TMIN to TMAX 0.05 -0.1 IOUT = 5mA IOUT = 50mA VCC - 0.5 IOUT = 250µA, VCC < VBATT - 0.2V VBATT - 0.1 VBATT - 0.02 VCC < VRT 2 VCC - 0.25 Power-up 20 Power-down -20 40 VRT 4.65 4.75 MAX692A, MAX802M MAX802L, TA = +25°C, VCC falling 4.25 4.40 4.50 MAX802M, TA = +25°C, VCC falling 4.30 4.70 140 VCC - 1.5 µA V V V 4.45 40 tRS µA mV 4.50 4.55 µA mV MAX690A, MAX802L, MAX805L ISOURCE = 800µA RESET Output Voltage 0.02 -1.0 0.02 VCC - 0.05 VCC - 0.025 Reset Threshold Hysteresis Reset Pulse Width 1.0 5.0 Battery Switchover Hysteresis Reset Threshold TYP 200 mV 280 ISINK = 3.2mA 0.4 MAX69_AC, MAX802_C, VCC = 1.0V ISINK = 50µA 0.3 MAX69_AE/M, MAX802_E, VCC = 1.2V, ISINK = 100µA 0.3 _______________________________________________________________________________________ ms V Microprocessor Supervisory Circuits (V CC = 4.75V to 5.5V for MAX690A/MAX802L/MAX805L, V CC = 4.5V to 5.5V for MAX692A/MAX802M, V BATT = 2.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MAX805LC, ISOURCE = 4µA, VCC = 1.1V MAX805LE/M, ISOURCE = 4µA, VCC = 1.2V RESET Output Voltage MAX805L, ISOURCE = 800µA MIN TYP 0.9 VCC - 1.5 tWD WDI Pulse Width tWP WDI Input Threshold (Note 4) 0.4 1.00 VIL = 0.4V, VIH = (0.8) (VCC) VCC = 5V PFI Input Threshold 3.5 50 150 -150 1.20 1.25 1.30 MAX802_C/E, VCC = 5V 1.225 1.250 1.275 -25 VCC - 1.5 0.01 25 ISOURCE = 800µA ISINK = 3.2mA sec ns 0.8 WDI = 0V MAX69_A, MAX805L, VCC = 5V PFI Input Current PFO Output Voltage 2.25 50 WDI = VCC WDI Input Current 1.60 Logic low Logic high UNITS V MAX805L, ISINK = 3.2mA Watchdog Timeout MAX 0.8 -50 0.4 V µA V nA V Note 2: Either VCC or VBATT can go to 0V, if the other is greater than 2.0V. Note 3: "-" = battery-charging current, "+" = battery-discharging current. Note 4: WDI is guaranteed to be in an intermediate, non-logic level state if WDI is floating and VCC is in the operating voltage range. WDI is internally biased to 35% of VCC with an input impedance of 50kΩ. _______________________________________________________________________________________ 3 MAX690A/MAX692A/MAX802L/MAX802M/MAX805L ELECTRICAL CHARACTERISTICS (continued) __________________________________________Typical Operating Characteristics OUTPUT VOLTAGE vs. LOAD CURRENT 5.00 2.78 VOUT (V) 4.90 4.85 VBATT = OV TA = +25°C VCC = 0V VBATT = +2.8V TA = +25°C VCC 2.76 +5V 0V VCC VCC 2.74 SLOPE = 80Ω GND 0V 2.70 0 10 20 40 30 0 50 0.4 0.2 IOUT (mA) 0.6 0.8 1.0 500ms/div IOUT (mA) MAX690A RESET RESPONSE TIME POWER-FAIL COMPARATOR RESPONSE TIME +5V VCC POWER-FAIL COMPARATOR RESPONSE TIME +5V PFO VCC RESET GND PFI PFO PFO 1k 30pF RESET 30pF +1.30V PFI +0V 0V PFI +1.2V 2µs/div +1.20V 400ns/div MAX805L RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE 400ns/div MAX805L RESET RESPONSE TIME +5V VCC 1V/div +5V 10k +5V VCC 0V +4V VCC RESET GND 10k 330pF +4V 330 pF 1V/div RESET 0V 0V 500ms/div 4 +3V +1.3V VCC = +5V TA = +25°C 0V VCC VBATT RESET GND 1k +1.25V 30pF +1.25V 10k 0V VCC = +5V TA = +25°C PFO +4V TA = +25°C VCC +5V PFI +5V +5V RESET 330pF RESET RESET 2.72 4.75 2k 1V/div SLOPE = 5Ω 4.80 1V/div VOUT (V) +5V 2.80 VCC = +5V VBATT = +2.8V TA = +25°C 4.95 RESET MAX690A RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE OUTPUT VOLTAGE vs. LOAD CURRENT 1V/div MAX690A/MAX692A/MAX802L/MAX802M/MAX805L Microprocessor Supervisory Circuits 2µs/div _______________________________________________________________________________________ Microprocessor Supervisory Circuits PIN NAME FUNCTION 1 VOUT Supply Output for CMOS RAM. When VCC is above the reset threshold, VOUT connects to VCC through a P-channel MOSFET switch. When VCC is below the reset threshold, the higher of VCC or VBATT will be connected to VOUT. 2 2 VCC +5V Supply Input 3 3 GND Ground 4 4 PFI Power-Fail Comparator Input. When PFI is less than 1.25V, PFO goes low. Connect PFI to GND or VCC when not used. 5 5 PFO Power-Fail Output. When PFI is less than 1.25V, PFO goes low; otherwise PFO stays high. WDI Watchdog Input. If WDI remains high or low for 1.6sec, the internal watchdog timer runs out and reset is triggered. If WDI is left floating or connected to a high-impedance three-state buffer, the watchdog feature is disabled. The internal watchdog timer clears whenever reset is asserted, WDI is three-stated, or WDI sees a rising or falling edge. RESET Reset Output. Whenever RESET is triggered, it pulses low for 200ms. It stays low when VCC is below the reset threshold (4.65V in the MAX690A/MAX802L and 4.4V in the MAX692A/MAX802M) and remains low for 200ms after VCC rises above the reset threshold. A watchdog timeout also triggers RESET. Active-High Reset Output is the inverse of RESET. When RESET is asserted, the RESET output voltage = VCC or VBATT, whichever is higher. MAX690A/MAX692A MAX802L/MAX802M MAX805L 1 6 6 7 – 7 RESET 8 8 VBATT Backup-Battery Input. When VCC falls below the reset threshold, VBATT will be switched to VOUT if VBATT is 20mV greater than VCC. When VCC rises to 20mV above VBATT, VOUT will be reconnected to VCC. The 40mV hysteresis prevents repeated switching if VCC falls slowly. _______________________________________________________________________________________ 5 MAX690A/MAX692A/MAX802L/MAX802M/MAX805L ______________________________________________________________Pin Description MAX690A/MAX692A/MAX802L/MAX802M/MAX805L Microprocessor Supervisory Circuits VBATT +5V BATTERY-SWITCHOVER CIRCUITRY VOUT VCC 0V VCC RESET GENERATOR 3.5V RESET (RESET) 1.25V 0V +5V tRS 3.0V RESET 0V +5V (RESET) WATCHDOG TIMER WDI VOUT 3.0V 0V MAX690A MAX692A MAX802L MAX802M MAX805L 0.8V PFI +5V PFO PFO 0V 1.25V ( ) ARE FOR MAX805L ONLY. GND ( ) ARE FOR MAX805L ONLY. Figure 1. Block Diagram Figure 2. Timing Diagram _______________Detailed Description Reset Output A microprocessor’s (µP’s) reset input starts the µP in a known state. When the µP is in an unknown state, it should be held in reset. The MAX690A/MAX692A/MAX802L/ MAX802M assert reset during power-up and prevent code execution errors during power-down or brownout conditions. On power-up, once VCC reaches 1V, RESET is guaranteed to be a logic low. As VCC rises, RESET remains low. When VCC exceeds the reset threshold, an internal timer keeps RESET low for a time equal to the reset pulse width; after this interval, RESET goes high (Figure 2). If a brownout condition occurs (if VCC dips below the reset threshold), RESET is triggered. Each time RESET is triggered, it stays low for the reset pulse width interval. Any time VCC goes below the reset threshold, the internal timer restarts the pulse. If a brownout condition interrupts a previously initiated reset pulse, the reset pulse continues for another 200ms. On powerdown, once VCC goes below the threshold, RESET is guaranteed to be logic low until VCC droops below 1V. RESET is also triggered by a watchdog timeout. If a high or low is continuously applied to the WDI pin for 1.6sec, RESET pulses low. As long as RESET is assert6 VBATT = PFI = 3.0V IOUT = 0mA ed, the watchdog timer remains clear. When RESET comes high, the watchdog resumes timing and must be serviced within 1.6sec. If WDI is tied high or low, a RESET pulse is triggered every 1.8sec (tWD plus tRS). The MAX805L active-high RESET output is the inverse of the MAX690A/MAX692A/MAX802L/MAX802M RESET output, and is guaranteed to be valid with VCC down to 1.1V. Some µPs, such as Intel’s 80C51, require an active-high reset pulse. Watchdog Input The watchdog circuit monitors the µP’s activity. If the µP does not toggle the watchdog input (WDI) within 1.6sec, a reset pulse is triggered. The internal 1.6sec timer is cleared by either a reset pulse or by open circuiting the WDI input. As long as reset is asserted or the WDI input is open circuited, the timer remains cleared and does not count. As soon as reset is released or WDI is driven high or low, the timer starts counting. It can detect pulses as short as 50ns. Power-Fail Comparator The PFI input is compared to an internal 1.25V reference. If PFI is less than 1.25V, PFO goes low. The power-fail comparator is intended for use as an undervoltage detector to signal a failing power supply; it _______________________________________________________________________________________ Microprocessor Supervisory Circuits VCC +5V SW1 SW2 SW4 SW3 D1 VOUT VCC TO STATIC RAM D2 MAX690A MAX802L VBATT MAX805L RESET (RESET) SUBSTRATE MAX690A MAX802L MAX805L MAX692A MAX802M D3 TO µP + 0.1F VOUT GND CONDITION SW1/SW2 SW3/SW4 VCC > Reset Threshold Open Closed VCC < Reset Threshold and VCC > VBATT Open Closed VCC < Reset Threshold and VCC < VBATT Closed Open ( ) ARE FOR MAX805L ONLY. RESET THRESHOLD = 4.65V IN MAX690A/MAX802L/MAX805L. RESET THRESHOLD = 4.4V IN MAX692A/MAX802M Figure 3. Backup-Battery Switchover Block Diagram need not be dedicated to this function though, as it is completely separate from the rest of the circuitry. The external voltage divider drives PFI to sense the unregulated DC input to the +5V regulator (see Typical Operating Circuit). The voltage-divider ratio can be chosen such that the voltage at PFI falls below 1.25V just before the +5V regulator drops out. PFO then triggers an interrupt which signals the µP to prepare for power-down. To conserve backup-battery power, the power-fail detector comparator is turned off and PFO is forced low when VBATT connects to VOUT. Figure 4. Using a SuperCap as a Backup Power Source with a MAX690A/MAX802L/MAX805L and a +5V ±5% Supply than VCC. When VCC exceeds the reset threshold, it is connected to the MAX690A/MAX692A/MAX802L/MAX802M/MAX805L substrate, regardless of the voltage applied to VBATT (Figure 3). During this time, the diode (D1) between VBATT and the substrate will conduct current from VBATT to VCC if Table 1. Input and Output Status in Battery-Backup Mode SIGNAL VCC Disconnected from VOUT VOUT Connected to VBATT through an internal 80Ω PMOS switch VBATT Connected to VOUT. Current drawn from the battery is less than 1µA, as long as VCC < VBATT - 1V. Backup-Battery Switchover In the event of a brownout or power failure, it may be necessary to preserve the contents of RAM. With a backup battery installed at VBATT, the devices automatically switch RAM to backup power when VCC fails. As long as VCC exceeds the reset threshold, VOUT connects to VCC through a 5Ω PMOS power switch. Once VCC falls below the reset threshold, VCC or VBATT (whichever is higher) switches to VOUT. Unlike the MAX690/MAX692, the MAX690A/MAX692A/MAX802L/MAX802M/MAX805L don’t always connect VBATT to VOUT when VBATT is greater than VCC. VBATT connects to VOUT (through an 80Ω switch) only when VCC is below the reset threshold and VBATT is greater STATUS PFI Power-fail comparator is disabled. PFO Logic low RESET Logic low RESET Logic high (MAX805L only) WDI Watchdog timer is disabled _______________________________________________________________________________________ 7 MAX690A/MAX692A/MAX802L/MAX802M/MAX805L VBATT MAX690A/MAX692A/MAX802L/MAX802M/MAX805L Microprocessor Supervisory Circuits VIN +5V +5V R1 VOUT VCC VCC TO STATIC RAM MAX692A MAX802M PFI RESET VBATT TO µP R3 R2 C1* + 100k 0.1F MAX690 MAX692A MAX802L MAX802M MAX805L PFO GND GND TO µP *OPTIONAL +5V Figure 5. Using a SuperCap™ as a Backup Power Source with the MAX692A/MAX802M and a +5V ±10% Supply PFO 0V VBATT is 0.6V or greater than VCC. When VBATT connects to VOUT, backup mode is activated and the internal circuitry is powered from the battery (Table 1). When VCC is just below VBATT, the current drawn from VBATT is typically 30µA. When VCC drops to more than 1V below VBATT, the internal switchover comparator shuts off and the supply current falls to less than 1µA. __________Applications Information VL 0V VTRIP = 1.25/ R2 R2 + R2 VTRIP VIN VH R2 || R3 VIH = 1.25/ R1 + R2 || R3 VL − 1.25 5 − 1.25 1.25 + = R1 R3 R2 Figure 6. Adding Hysteresis to the Power-Fail Comparator Using a SuperCap™ as a Backup Power Source SuperCaps are capacitors with extremely high capacitance values, on the order of 0.1F. Figure 4 shows a SuperCap used as a backup power source. Do not allow the SuperCap’s voltage to exceed the maximum reset threshold by more than 0.6V. In Figure 4’s circuit, the SuperCap rapidly charges to within a diode drop of VCC. However, after a long time, the diode leakage current will pull the SuperCap voltage up to VCC. When using a SuperCap with the MAX690A/MAX802L/MAX805L, VCC may not exceed 4.75V + 0.6V = 5.35V. Use the SuperCap circuit of Figure 5 with a MAX692A or MAX802M and a ±10% supply. This circuit ensures that the SuperCap only charges to V CC 0.5V. At the maximum V CC of 5.5V, the SuperCap charges up to 5.0V, only 0.5V above the maximum reset threshold—well within the requisite 0.6V. Allowable Backup Power-Source Batteries Lithium batteries work very well as backup batteries due to very low self-discharge rates and high energy density. Single lithium batteries with open-circuit voltages of 3.0V to 3.6V are ideal. Any battery with an open-circuit voltage less than the minimum reset threshold plus 0.3V can be Table 2. Allowable Backup-Battery Voltages (see Using a SuperCap as a Backup Power Source section for use with a SuperCap) MAXIMUM BACKUP-BATTERY PART NO. VOLTAGE (V) MAX690A/ 4.80 MAX802L/MAX805L MAX692A/ 4.55 MAX802M ™SuperCap is a trademark of Baknor Industries. 8 _______________________________________________________________________________________ Microprocessor Supervisory Circuits Operation Without a Backup Power Source If a backup power source is not used, ground VBATT and connect VOUT to VCC. Since there is no need to switch over to any backup power source, VOUT does not need to be switched. A direct connection to VCC eliminates any voltage drops across the switch which may push VOUT below VCC. Replacing the Backup Battery The backup battery can be removed while VCC remains valid, without danger of triggering RESET/RESET. As long as VCC stays above the reset threshold, batterybackup mode cannot be entered. In other switchover +5V R1 VCC PFI R2 MAX690A MAX692A MAX802L MAX802M MAX805L PFO ICs where battery-backup mode is entered whenever VBATT gets close to VCC, an unconnected VBATT pin accumulates leakage charge and triggers RESET/RESET in error. Adding Hysteresis to the Power-Fail Comparator Hysteresis adds a noise margin to the power-fail comparator and prevents repeated triggering of PFO when VIN is close to its trip point. Figure 6 shows how to add hysteresis to the power-fail comparator. Select the ratio of R1 and R2 such that PFI sees 1.25V when VIN falls to its trip point (VTRIP). R3 adds the hysteresis. It will typically be an order of magnitude greater than R1 or R 2 (about 10 times either R 1 or R 2). The current through R1 and R2 should be at least 1µA to ensure that the 25nA (max) PFI input current does not shift the trip point. R3 should be larger than 10kΩ so it does not load down the PFO pin. Capacitor C1 adds additional noise rejection. Monitoring a Negative Voltage The power-fail comparator can be used to monitor a negative supply rail using the circuit of Figure 7. When the negative rail is good (a negative voltage of large magnitude), PFO is low. When the negative rail is degraded (a negative voltage of lesser magnitude), PFO goes high. This circuit’s accuracy is affected by the PFI threshold tolerance, the VCC line, and the resistors. Interfacing to µPs with Bidirectional Reset Pins µPs with bidirectional reset pins, such as the Motorola 68HC11 series, can contend with the MAX690A/MAX692A/MAX802L/MAX802M RESET output. If, for example, the RESET output is driven high and the µP wants to pull it low, indeterminate logic levels may result. To correct this, connect a 4.7kΩ resistor between the RESET output and the µP reset I/O, as in Figure 8. Buffer the RESET output to other system components GND V- +5V PFO 0V VTRIP V- 5 − 1.25 0V 1.25 - VTRIP = NOTE: R1 VTRIP IS NEGATIVE R2 Figure 7. Monitoring a Negative Voltage _______________________________________________________________________________________ 9 MAX690A/MAX692A/MAX802L/MAX802M/MAX805L connected directly to the V BATT input of the MAX690A/MAX692A/MAX802L/MAX802M/MAX805L with no additional circuitry (see the Typical Operating Circuit). However, batteries with open-circuit voltages that are greater cannot be used for backup, as current is sourced into the substrate through the diode (D1 in Figure 3) when VCC is close to the reset threshold. MAX690A/MAX692A/MAX802L/MAX802M/MAX805L Microprocessor Supervisory Circuits BUFFERED RESET TO OTHER SYSTEM COMPONENTS VCC MAX690A MAX692A MAX802L RESET MAX802M GND VCC 4.7k RESET GND Figure 8. Interfacing to µPs with Bidirectional Reset I/O 10 ______________________________________________________________________________________ Microprocessor Supervisory Circuits Part Number Minimum Nominal Reset Reset Pulse Threshold Width (V) (ms) Nominal Watchdog Timeout Backup- CE Period Battery Write (sec) Switch Protect MAX690A/692A 4.65/4.40 140 1.6 ✔ MAX691A/693A 4.65/4.40 140/adj. 1.6/adj. ✔ MAX696 Adj. 35/adj. 1.6/adj. ✔ MAX697 Adj. 35/adj. 1.6/adj. MAX700 4.65/adj. 200 - MAX703/704 4.65/4.40 140 - MAX705/706 4.65/4.40 140 MAX706P 2.63 140 MAX706R/S/T 2.63/2.93/ 3.08 MAX707/708 MAX708R/S/T MAX709L/M/ R/S/T PowerFail Comparator Manual- Watch- LowReset dog Line Input Output Output Active- BatteryHigh On Reset Output ✔ ✔/10ns ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ 1.6 ✔ ✔ ✔ 1.6 ✔ ✔ ✔ 140 1.6 ✔ ✔ ✔ 4.65/4.40 140 - ✔ ✔ ✔ 2.63/2.93/ 3.08 140 - ✔ ✔ ✔ 4.65/4.40/ 140 2.63/2.93/3.08 ✔ ✔/10ns ✔ ✔ ✔ ✔ ✔ ✔/10ns ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ MAX791 4.65 140 1 MAX792L/M/ R/S/T 4.65/4.40/ 140 2.63/2.93/3.08 1 MAX800L/M 4.60/4.40 140 1.6/adj. ✔ MAX802L/M 4.60/4.40 140 1.6 ✔ ✔/±2% MAX805L 4.65 140 1.6 ✔ ✔ MAX813L 4.65 140 1.6 MAX820L/M/ R/S/T 4.65/4.40/ 140 2.63/2.93/3.08 1 MAX1232 4.37/4.62 250 0.15/0.60/1.2 MAX1259 - - - ✔/10ns ✔/10ns ✔/±2% ✔ ✔ ✔ ✔ ✔ ✔ ✔/±2% ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ______________________________________________________________________________________ 11 MAX690A/MAX692A/MAX802L/MAX802M/MAX805L ________________________µ P Supervisory Circuits MAX690A/MAX692A/MAX802L/MAX802M/MAX805L Microprocessor Supervisory Circuits __Ordering Information (continued) PART TEMP. RANGE MAX692ACPA 0°C to +70°C 8 Plastic DIP MAX692ACSA 0°C to +70°C 8 SO MAX692AC/D 0°C to +70°C MAX692AEPA -40°C to +85°C 8 Plastic DIP MAX692AESA -40°C to +85°C 8 SO MAX692AMJA -55°C to +125°C 8 CERDIP** MAX802LCPA 0°C to +70°C 8 Plastic DIP MAX802LCSA 0°C to +70°C 8 SO MAX802LEPA -40°C to +85°C MAX802LESA -40°C to +85°C MAX802MCPA ____________________Chip Topography PIN-PACKAGE V CC V OUT V BATT Dice* RESET (RESET) 0.061" WDI (1.55mm) GND 8 Plastic DIP 8 SO 0°C to +70°C 8 Plastic DIP MAX802MCSA 0°C to +70°C 8 SO MAX802MEPA -40°C to +85°C MAX802MESA -40°C to +85°C MAX805LCPA 0°C to +70°C 8 Plastic DIP MAX805LCSA 0°C to +70°C 8 SO MAX805LC/D 0°C to +70°C MAX805LEPA -40°C to +85°C 8 Plastic DIP 8 SO PFI PFO 0.078" (1.98mm) ( ) ARE FOR MAX805L ONLY. TRANSISTOR COUNT: 573; SUBSTRATE MUST BE LEFT UNCONNECTED. Dice* 8 Plastic DIP MAX805LESA -40°C to +85°C 8 SO MAX805LMJA -55°C to +125°C 8 CERDIP** * Dice are specified at TA = +25°C. **Contact factory for availability and processing to MIL-STD-883. Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1993 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.