19-0099; Rev 5; 4/06 +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits Features The MAX706P/R/S/T, MAX706AP/AR/AS/AT, and MAX708R/S/T microprocessor (µP) supervisory circuits reduce the complexity and number of components required to monitor +3V power-supply levels in +3V to +5V µP systems. These devices significantly improve system reliability and accuracy compared to separate ICs or discrete components. ♦ µMAX Package, Small 8-Pin SO The MAX706P/R/S/T and MAX706AP/AR/AS/AT supervisory circuits provide the following four functions: 1) A reset output during power-up, power-down, and brownout conditions. 2) An independent watchdog output that goes low if the watchdog input has not been toggled within 1.6s. 3) A 1.25V threshold detector for power-fail warning, low-battery detection, or for monitoring a power supply other than the main supply. 4) An active-low, manual-reset input. ♦ Debounced TTL/CMOS-Compatible Manual Reset Input The only difference between the MAX706R/AR, MAX706S/AS, and MAX706T/AT is the reset-threshold voltage levels, which are 2.63V, 2.93V, and 3.08V, respectively. All have active-low reset output signals. The MAX706P/AP are identical to the MAX706R/AR, except the reset output signal is active-high. The watchdog timer function for the MAX706AP/AR/AS/AT disables when the WDI input is left open or connected to a high-impedance state of a low-leakage tri-state output. The MAX708R/S/T provide the same functions as the MAX706R/S/T and MAX706AR/AS/AT except they do not have a watchdog timer. Instead, they provide both RESET and RESET outputs. As with the MAX706, devices with R, S, and T suffixes have reset thresholds of 2.63V, 2.93V, and 3.08V, respectively. These devices are available in 8-pin SO, DIP, and µMAX® packages and are fully specified over the operating temperature range. ♦ Precision Supply-Voltage Monitors 2.63V (MAX706P/R, MAX706AP/AR, and MAX708R) 2.93V (MAX706S, MAX706AS, and MAX708S) 3.08V (MAX706T, MAX706AT, and MAX708T) ♦ 200ms Reset Time Delay ♦ 100µA Quiescent Current ♦ WDI Disable Feature (MAX706AP/AR/AS/AT) ♦ Watchdog Timer: 1.6s Timeout ♦ Reset Output Signal: Active-High Only (MAX706P, MAX706AP) Active-Low Only (MAX706R/S/T, MAX706AR/AS/AT) Active-High and Active-Low (MAX708R/S/T) ♦ Voltage Monitor for Power-Fail or Low-Battery Warning ♦ 8-Pin Surface-Mount Package ♦ Guaranteed RESET Assertion to VCC = 1V Ordering Information PART† TEMP RANGE MAX706PCPA 0°C to +70°C 8 PDIP P8-1 MAX706PCSA 0°C to +70°C 8 SO S8-2 MAX706PCUA 0°C to +70°C 8 µMAX U8-1 MAX706PEPA -40°C to +85°C 8 PDIP P8-1 Portable Instruments PKG CODE †SO, µMAX, and PDIP packages are available in lead-free. Ordering Information continued at end of data sheet. Pin Configurations appear at end of data sheet. Typical Operating Circuits Applications Battery-Powered Equipment PINPACKAGE UNREGULATED DC MAX639 DC-DC CONVERTER +3V/+3.3V VCC Computers Controllers Intelligent Instruments VCC Critical µP Power Monitoring PFI PUSHBUTTON SWITCH µMAX is a registered trademark of Maxim Integrated Products, Inc. µP MAX706R/S/T MAX706AR/AS/AT MR RESET WDI WDO PFO GND RESET I/O LINE NMI INTERRUPT Typical Operating Circuits continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T General Description MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits ABSOLUTE MAXIMUM RATINGS Terminal Voltage (with respect to GND) VCC ........................................................................-0.3V to +6V All Other Inputs (Note 1)..........................-0.3V to (VCC + 0.3V) Input Current VCC ..................................................................................20mA GND .................................................................................20mA Output Current (all outputs) ................................................20mA Continuous Power Dissipation (TA = +70°C) 8-Pin CERDIP (derate 8mW/°C above +70°C)..............640mW 8-Pin PDIP (derate 9.1mW/°C above +70°C).............727.3mW 8-Pin SO (derate 5.9mW/°C above +70°C)................470.6mW 8-Pin µMAX (derate 4.5mW/oC above +70°C) ..............362mW Operating Temperature Range MAX70_C .............................................................0°C to +70°C MAX70_E ..........................................................-40°C to +85°C MAX70_M .......................................................-55°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: The input-voltage limits on PFI, WDI, and MR can be exceeded if the input current is 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 (MAX70_P/R, MAX706AP/AR: VCC = 2.7V to 5.5V; MAX70_S, MAX706AS: VCC = 3.0V to 5.5V; MAX70_T, MAX706AT: VCC = 3.15V to 5.5V; TJ = TA = TMIN to TMAX, unless otherwise noted. Typical values are at TJ = TA = +25°C.) (Note 2) PARAMETER Supply Voltage Range SYMBOL CONDITIONS VCC VCC < 3.6V Supply Current ISUPPLY VCC < 5.5V Reset Threshold (Note 3) (VCC Falling) VRST Reset Threshold Hysteresis (Note 3) VHYS Reset Pulse Width (Note 3) tRST MIN TYP MAX MAX70_C 1.0 5.5 MAX70_E/M 1.2 5.5 MAX706_C 90 200 MAX706_E/M 90 300 MAX708_C 50 200 MAX708_E/M 50 300 MAX706_C 135 350 MAX706_E/M 135 500 MAX708_C 65 350 MAX708_E/M 65 500 MAX70_P/R/, MAX706AP/AR 2.55 2.63 2.70 MAX70_S, MAX706AS 2.85 2.93 3.00 MAX70_T, MAX706AT 3.00 3.08 3.15 20 V µA V mV MAX70_P/R/, MAX706AP/AR VCC = 3.0V 140 200 280 MAX70_S, MAX706AS, VCC = 3.3V 140 200 280 VCC = 5V UNITS ms 200 RESET OUTPUT Output-Voltage High (MAX70_R/S/T) (MAX706AR/AS/AT) VOH VRST(MAX) < VCC < 3.6V ISOURCE = 500µA VOL VRST(MAX) < VCC < 3.6V ISINK = 1.2mA VOH 4.5V < VCC < 5.5V IRSOURCE = 800µA VOL 4.5V < VCC < 5.5V ISINK = 3.2mA VOL 2 0.8 x VCC 0.3 VCC 1.5 V 0.4 MAX70_C VCC = 1.0V, ISINK = 50µA 0.3 MAX70_E/M: VCC = 1.2V, ISINK = 100µA 0.3 _______________________________________________________________________________________ +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits (MAX70_P/R, MAX706AP/AR: VCC = 2.7V to 5.5V; MAX70_S, MAX706AS: VCC = 3.0V to 5.5V; MAX70_T, MAX706AT: VCC = 3.15V to 5.5V; TJ = TA = TMIN to TMAX, unless otherwise noted. Typical values are at TJ = TA = +25°C.) (Note 2) PARAMETER Output-Voltage High (MAX706P) (MAX706AP) Output-Voltage High (MAX708_) SYMBOL CONDITIONS MIN VOH VRST(MAX) < VCC < 3.6V ISOURCE = 215µA VCC 0.6 VOL VRST(MAX) < VCC < 3.6V ISINK = 1.2mA VOH 4.5 < VCC < 5.5V ISOURCE = 800µA ISINK = 3.2mA TYP MAX 0.3 UNITS V VCC 1.5 VOL 4.5V < VCC < 5.5V VOH VRST(MAX) < VCC < 3.6V ISOURCE = 500µA 0.8 x VCC VOL VRST(MAX) < VCC < 3.6V ISINK = 500µA VOH 4.5V < VCC < 5.5V ISOURCE = 800µA VOL 4.5V < VCC < 5.5V ISINK = 1.2mA 0.4 0.3 V VCC 1.5 0.4 WATCHDOG INPUT MAX706P/R, MAX706AP/AR, VCC = 3.0V 1.00 1.60 2.25 1.00 1.60 2.25 VIL MAX706S/T, MAX706AS/AT, VCC = 3.3V VRST(MAX) < VCC VIL = 0.4V < 3.6V 4.5V < VCC < VIH = 0.8V x VCC 5.5V VRST(MAX) < VCC < 3.6V VIH VRST(MAX) < VCC < 3.6V VIL VCC = 5.0V VIH VCC = 5.0V Watchdog Timeout Period tWD WDI Pulse Width (MAX706_, MAX706A_) tWP Watchdog Input Threshold (MAX706_, MAX706A_) WDI Input Current WDI = 0V or VCC s 100 ns 50 0.6 0.7 x VCC V 0.8 3.5 MAX706_ MAX706A_ -1.0 -5 +0.02 +1.0 +5 µA _______________________________________________________________________________________ 3 MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T ELECTRICAL CHARACTERISTICS (continued) MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits ELECTRICAL CHARACTERISTICS (continued) (MAX70_P/R, MAX706AP/AR: VCC = 2.7V to 5.5V; MAX70_S, MAX706AS: VCC = 3.0V to 5.5V; MAX70_T, MAX706AT: VCC = 3.15V to 5.5V; TJ = TA = TMIN to TMAX, unless otherwise noted. Typical values are at TJ = TA = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN VOH VRST(MAX) < VCC < 3.6V ISOURCE = 500µA 0.8 x VCC VOL VRST(MAX) < VCC < 3.6V ISINK = 500µA TYP MAX UNITS WATCHDOG OUTPUT WDO Output Voltage (MAX706_, MAX706A_) VOH 4.5V < VCC < 5.5V ISOURCE = 800µA VOL 4.5V < VCC < 5.5V ISINK = 1.2mA 0.3 V VCC 1.5 0.4 MANUAL RESET INPUT MR Pullup Current MR Pulse Width MR = 0 tMR VIL MR Input Threshold MR to Reset Output Delay 25 70 250 4.5V < VCC < 5.5V 100 250 600 µA VRST(MAX) < VCC < 3.6V 500 4.5V < VCC < 5.5V 150 ns VRST(MAX) < VCC < 3.6V VIH VRST(MAX) < VCC < 3.6V VIL 4.5V < VCC < 5.5V VIH 4.5V < VCC < 5.5V tMD VRST(MAX) < VCC < 3.6V 0.6 0.7 x VCC V 0.8 2.0 VRST(MAX) < VCC < 3.6V 750 4.5V < VCC < 5.5V 250 ns POWER-FAILURE COMPARATOR PFI Input Threshold (MAX70_P/R, MAX706AP/AR) PFI falling VCC = 3.0V 1.20 1.25 1.30 (MAX70_S/T, MAX706AS/AT) PFI falling, VCC = 3.3V 1.20 1.25 1.30 -25 +0.01 +25 PFI Input Current PFO Output Voltage VOH VRST(MAX) < VCC < 3.6V ISOURCE = 500µA VOL VRST(MAX) < VCC < 3.6V ISINK = 1.2mA VOH 4.5V < VCC < 5.5V ISOURCE = 800µA VOL 4.5V < VCC < 5.5V ISINK = 3.2mA V 0.8 x VCC 0.3 VCC 1.5 Note 2: All devices 100% production tested at TA = +85°C. Limits over temperature are guaranteed by design. Note 3: Applies to both RESET in the MAX70_R/S/T and MAX706AR/AS/AT, and RESET in the MAX706P/MAX706AP. 4 nA _______________________________________________________________________________________ 0.4 V +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits _______________________________________________________________________________________ 5 MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T Pin Description PIN MAX706P MAX706AP SO/DIP µMAX SO/DIP µMAX MAX708R/S/T MR 4 VCC Supply Voltage Input 5 GND Ground 1 3 1 3 2 4 2 4 2 3 5 3 5 3 5 7 4 5 6 7 FUNCTION Active-Low, Manual-Reset Input. Pull MR below 0.6V to trigger a reset pulse. MR is TTL/CMOS compatible when VCC = 5V and can be shorted to GND with a switch. MR is internally connected to a 70µA source current. Connect to VCC or leave unconnected. 3 6 NAME SO/DIP µMAX 1 4 6 MAX706R/S/T, MAX706AR/AS/AT 4 5 6 7 6 8 6 8 — — 7 1 — — 8 2 8 2 8 2 — — — — 7 1 7 1 — — — — 6 8 PFI Adjustable Power-Fail Comparator Input. Connect PFI to a resistive divider to set the desired PFI threshold. When PFI is less than 1.25V, PFO goes low and sinks current; otherwise, PFO remains high. Connect PFI to GND if not used. PFO Active-Low, Power-Fail Comparator Output. PFO asserts when PFI is below the internal 1.25V threshold. PFO deasserts when PFI is above the internal 1.25V threshold. Leave PFO unconnected if not used. WDI Watchdog Input. A falling or rising transition must occur at WDI within 1.6s to prevent WDO from asserting (see Figure 4). The internal watchdog timer is reset to zero when reset is asserted or when transition occurs at WDI. The watchdog function for the MAX706P/R/S/T can not be disabled. The watchdog timer for the MAX706AP/AR/AS/AT disables when WDI input is left open or connected to a tri-state output in its high-impedance state with a leakage current of less than 600nA. Active-High Reset Output. Reset remains high when VCC is RESET below the reset threshold or MR is held low. It remains low for 200ms after the reset conditions end (Figure 3). WDO Active-Low Watchdog Output. WDO goes low when a transition does not occur at WDI within 1.6s and remains low until a transition occurs at WDI (indicating the watchdog interrupt has been serviced). WDO also goes low when VCC falls below the reset threshold; however, unlike the reset output signal, WDO goes high as soon as VCC rises above the reset threshold. Active-Low Reset Output. RESET remains low when VCC is RESET below the reset threshold or MR is held low. It remains low for 200ms after the reset conditions end (Figure 3). N.C. No Connection. Not internally connected. _______________________________________________________________________________________ +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits 6 WATCHDOG TRANSITION DETECTOR VCC 70µA MR VCC PFI WATCHDOG TIMER 8 WDO VCC MR 1 2 4 RESET 70µA TIMEBASE FOR RESET AND WATCHDOG RESET GENERATOR 8 7 VCC RESET GENERATOR 2 7 RESET RESET (RESET) 2.63V MAX706P/R 2.93V MAX706S MAX706P/R/S/T 3.08V MAX706T MAX706AP/AR/AS/AT PFI 5 1 PFO 4 2.63V MAX708R 2.93V MAX708S 3.08V MAX708T MAX708R/S/T 5 PFO 1.25V 1.25V 3 GND ( ) ARE FOR MAX706P/AP. 3 GND Figure 1. MAX706_ Functional Diagram RESET and RESET Outputs A microprocessor’s (µP’s) reset input starts in a known state. When the µP is in an unknown state, it should be held in reset. The MAX706P/R/S/T and the MAX706AP/ AR/AS/AT assert reset when V CC is low, preventing code execution errors during power-up, power-down, or brownout conditions. On power-up once VCC reaches 1V, RESET is guaranteed to be logic-low and RESET is guaranteed to be logic-high. As VCC rises, RESET and RESET remain asserted. Once VCC exceeds the reset threshold, the internal timer causes RESET and RESET to be deasserted after a time equal to the reset pulse width, which is typically 200ms (Figure 3). If a power-fail or brownout condition occurs (i.e., VCC drops below the reset threshold), RESET and RESET are asserted. As long as VCC remains below the reset threshold, the internal timer is continually reset, causing the RESET and RESET outputs to remain asserted. Thus, a brownout condition that interrupts a previously initiated reset pulse causes an additional 200ms delay from the time the latest interruption occurred. On power-down once VCC drops below the reset threshold, Figure 2. MAX708_ Functional Diagram RESET and RESET are guaranteed to be asserted for VCC ≥ 1V. The MAX706P/MAX706AP provide a RESET signal, and the MAX706R/S/T and MAX706AR/AS/AT provide a RESET signal. The MAX708R/S/T provide both RESET and RESET. Watchdog Timer The MAX706P/R/S/T and the MAX706AP/AR/AS/AT watchdog circuit monitor the µP’s activity. If the µP does not toggle the watchdog input (WDI) within 1.6s, the watchdog output (WDO) goes low (Figure 4). If the reset signal is asserted, the watchdog timer will be reset to zero and disabled. As soon as reset is released, the timer starts counting. WDI can detect pulses as narrow as 100ns with a 2.7V supply and 50ns with a 4.5V supply. The watchdog timer for the MAX706P/R/S/T cannot be disabled. The watchdog timer for the MAX706AP/AR/AS/AT operates similarly to the MAX706P/R/S/T. However, the watchdog timer for the MAX706AP/AR/AS/AT disables when the WDI input is left open or connected to a tri-state output in its highimpedance state and with a leakage current of less than 600nA. The watchdog timer can be disabled anytime, provided WDO is not asserted. _______________________________________________________________________________________ 7 MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T WDI MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits +3.3V VCC +1V VRST VRST tRST tRST +12V +3V/+3.3V RESET 0V +3.3V TO µP MAX706_ MAX708R/S/T RESET 0V MR 130kΩ 1% +3.3V MR* 0V PFI PFO GND tMD tMR +3.3V WDO* RESET (RESET) VCC 1MΩ 1% *NOTE: MR EXTERNALLY DRIVEN LOW. WDO TIMING SHOWN FOR MAX706P/R/S/T. 0V Figure 3. RESET, RESET, MR, and WDO Timing tWP tWD tWD PARAMETER MIN TYP MAX UNIT +12V RESET 10.24 THRESHOLD AT +25°C 10.87 11.50 V ( ) ARE FOR MAX706P/AP tWD +3V/+3.3V WDI 0V Figure 5. Monitoring Both +3V/+3.3V and +12V +3V/+3.3V WDO 0V +3V/+3.3V RESET 0V RESET EXTERNALLY TRIGGERED BY MR tRST MAX706R/S/T MAX708R/S/T MAX706AR/AS/AT RESET Figure 4. MAX706AP/AR/AS/AT Watchdog Timing WDO can be connected to the nonmaskable interrupt (NMI) input of a µP. When VCC drops below the reset threshold, WDO immediately goes low, even if the watchdog timer has not timed out (Figure 3). Normally, this would trigger an NMI, but since reset is asserted simultaneously, the NMI is overridden. The WDO should not be connected to RESET directly. Instead, connect WDO to MR to generate a reset pulse when it times out. Manual Reset The manual reset (MR) input allows RESET and RESET to be activated by a pushbutton switch. The switch is effectively debounced by the 140ms minimum reset pulse width. MR can be driven by an external logic line since it is TTL/CMOS compatible. The minimum MR 8 R1 Figure 6. RESET Valid to GND Circuit input pulse width is 500ns when VCC = +3V and 150ns when VCC = +5V. Leave MR unconnected or connect to VCC when not used. Power-Fail Comparator The power-fail comparator can be used for various purposes because its output and noninverting input are not internally connected. The inverting input is internally connected to a 1.25V reference. The power-fail comparator has 10mV of hysteresis, which prevents repeated triggering of the power-fail output (PFO). _______________________________________________________________________________________ +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits Regulated and unregulated voltages can be monitored by simply adjusting the PFI resistive-divider network values to the appropriate ratio. In addition, the reset signal can be asserted at voltages other that VCC reset threshold, as shown in Figure 5. Connect PFO to MR to initiate a reset pulse when the 12V supply drops below a user-specified threshold (11V in this example) or when VCC falls below the reset threshold. VIN MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T To build an early-warning power-failure circuit, use the power-fail comparator input (PFI) to monitor the unregulated DC supply voltage (see the Typical Operating Circuits). Connect the PFI to a resistive-divider network such that the voltage at PFI falls below 1.25V just before the regulator drops out. Use PFO to interrupt the µP so it can prepare for an orderly power-down. +3V/+3.3V R1 VCC PFI C1* MAX706_ MAX708R/S/T R3 R2 PFO GND TO µP *OPTIONAL +3V/+3.3V PFO Operation with +3V and +5V Supplies The MAX706P/R/S/T, the MAX706AP/AR/AS/AT, and the MAX708R/S/T provide voltage monitoring at the reset threshold (2.63V to 3.08V) when powered from either +3V or +5V. These devices are ideal in portable-instrument applications where power can be supplied from either a +3V battery or an AC-DC wall adapter that generates +5V (a +5V supply allows a µP or a microcontroller to run faster than a +3V supply). With a +3V supply, these ICs consume less power, but output drive capability is reduced, the MR to RESET delay time increases, and the MR minimum pulse width increases. The Electrical Characteristics table provides specifications for operation with both +3V and +5V supplies. 0V 0V VTRIP = 1.25 Applications Information Adding Hysteresis to the Power-Fail Comparator Hysteresis adds a noise margin to the power-fail comparator and prevents repeated triggering of the PFO when VIN is near the power-fail comparator trip point. Figure 7 shows how to add hysteresis to the power-fail comparator. Select the ratio of R1 and R2 such that PFI (R1 + R2) R2 VH = 1.25 (1 + R3 + R2 R1) VL = 1.25 + R1 1.25 - VCC - 1.25 R2 × R3 R2 R3 Figure 7. Adding Hysteresis to the Power-Fail Comparator +3V/+3.3V Ensuring a Valid RESET Output Down to VCC = 0V When V CC falls below 1V, the MAX706R/S/T, MAX706AR/AS/AT, and MAX708R/S/T RESET output no longer sinks current; it becomes an open circuit. Highimpedance, CMOS logic inputs can drift to undetermined voltages if left as open circuit. If a pulldown resistor is added to the RESET pin , as shown in Figure 6, any stray charge or leakage current will flow to ground, holding RESET low. Resistor value R is not critical, but it should not load RESET and should be small enough to pull RESET and the input it is driving to ground. 100kΩ is suggested for R1. VL VTRIP VH VIN R1 VCC PFO PFI MAX706_ MAX708R/S/T R2 GND +3V/+3.3V V- PFO 0V VTRIP VCC - 1.25 1.25 - VTRIP = R1 R2 0V V- NOTE: VTRIP IS NEGATIVE. Figure 8. Monitoring a Negative Voltage _______________________________________________________________________________________ 9 MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits sees 1.25V when V IN falls to the desired trip point (VTRIP). Resistor R3 adds hysteresis. R3 will typically be an order of magnitude greater than R1 and R2. 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 significantly. R3 should be larger than 10kΩ to prevent it from loading down the PFO pin. Capacitor C1 adds noise rejection. Monitoring a Negative Voltage The power-fail comparator can be used to monitor a negative supply voltage using the circuit of Figure 8. When the negative supply is valid, PFO is low. When the negative supply voltage drops, PFO goes high. This circuit’s accuracy is affected by the PFI threshold tolerance, the VCC voltage, and resistors R1 and R2. Bypassing VCC For noisy systems, bypass VCC with a 0.1µF capacitor to GND. Ordering Information (continued) PART† MAX706PEUA MAX706PMJA MAX706RCPA TEMP RANGE -40°C to +85°C PINPACKAGE 8 µMAX -55°C to +125°C 8 CERDIP* 0°C to +70°C 8 Plastic Dip PKG CODE TEMP RANGE PART† PINPACKAGE PKG CODE U8-1 MAX706ASESA -40°C to +85°C 8 SO S8-2 J8-2 MAX706ASEUA -40°C to +85°C 8 µMAX U8-1 P8-1 MAX706ATEPA -40°C to +85°C 8 Plastic Dip P8-1 -40°C to +85°C 8 SO S8-2 0°C to +70°C 8 SO S8-2 MAX706ATESA MAX706RCUA 0°C to +70°C 8 µMAX U8-1 MAX706ATEUA -40°C to +85°C 8 µMAX U8-1 MAX706REPA -40°C to +85°C 8 Plastic Dip P8-1 MAX708RCPA 0°C to +70°C 8 Plastic Dip P8-1 0°C to +70°C 8 SO S8-2 MAX706RCSA MAX706RESA MAX706REUA MAX706RMJA -40°C to +85°C 8 SO S8-2 MAX708RCSA -40°C to +85°C 8 µMAX U8-1 MAX708RCUA 0°C to +70°C 8 µMAX U8-1 J8-2 MAX708REPA -40°C to +85°C 8 Plastic Dip P8-1 P8-1 MAX708RESA -40°C to +85°C 8 SO S8-2 8 µMAX U8-1 -55°C to +125°C 8 CERDIP* MAX706SCPA 0°C to +70°C 8 Plastic Dip MAX706SCSA 0°C to +70°C 8 SO S8-2 MAX708REUA -40°C to +85°C MAX706SCUA 0°C to +70°C 8 µMAX U8-1 MAX708RMJA -55°C to +125°C 8 CERDIP* J8-2 0°C to +70°C 8 Plastic Dip P8-1 MAX706SEPA -40°C to +85°C 8 Plastic Dip P8-1 MAX708SCPA MAX706SESA -40°C to +85°C 8 SO S8-2 MAX708SCSA 0°C to +70°C 8 SO S8-2 MAX706SEUA -40°C to +85°C 8 µMAX U8-1 MAX708SCUA 0°C to +70°C 8 µMAX U8-1 J8-2 MAX708SEPA -40°C to +85°C 8 Plastic Dip P8-1 MAX706SMJA -55°C to +125°C 8 CERDIP* MAX706TCPA 0°C to +70°C 8 Plastic Dip P8-1 MAX708SESA -40°C to +85°C 8 SO S8-2 MAX706TCSA 0°C to +70°C 8 SO S8-2 MAX708SEUA -40°C to +85°C 8 µMAX U8-1 MAX706TCUA 0°C to +70°C 8 µMAX U8-1 MAX708SMJA -55°C to +125°C 8 CERDIP* J8-2 MAX706TEPA -40°C to +85°C 8 Plastic Dip P8-1 MAX708TCPA 0°C to +70°C 8 Plastic Dip P8-1 MAX706TESA -40°C to +85°C 8 SO S8-2 MAX708TCSA 0°C to +70°C 8 SO S8-2 U8-1 MAX708TCUA 0°C to +70°C 8 µMAX U8-1 J8-2 MAX708TEPA -40°C to +85°C 8 Plastic Dip P8-1 P8-1 MAX708TESA -40°C to +85°C 8 SO S8-2 MAX708TEUA -40°C to +85°C 8 µMAX U8-1 -55°C to +125°C 8 CERDIP* J8-2 MAX706TEUA MAX706TMJA MAX706APEPA -40°C to +85°C 8 µMAX -55°C to +125°C 8 CERDIP* -40°C to +85°C 8 Plastic Dip MAX706APESA -40°C to +85°C 8 SO S8-2 MAX706APEUA -40°C to +85°C 8 µMAX U8-1 MAX708TMJA †SO, µMAX, and PDIP packages are available in lead-free. MAX706AREPA -40°C to +85°C 8 Plastic Dip P8-1 MAX706ARESA -40°C to +85°C 8 SO S8-2 *Contact factory for availability and processing to MIL-STD-883. **Future product—contact factory for availability. MAX706AREUA -40°C to +85°C 8µMAX U8-1 Chip Information MAX706ASEPA -40°C to +85°C 8 Plastic Dip P8-1 10 PROCESS: CMOS ______________________________________________________________________________________ +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits Typical Operating Circuits (continued) TOP VIEW MR 1 8 WDO VCC 2 7 RESET GND 3 MAX706P MAX706AP PFI 4 6 WDI 5 PFO UNREGULATED DC MAX639 DC-DC CONVERTER -3V/+3.3V µP VCC VCC DIP/SO RESET PFI MR 1 VCC 2 8 WDO 7 RESET MAX706R/S/T GND 3 MAX706AR/AS/AT 6 PFI 4 5 WDI PUSHBUTTON SWITCH RESET RESET MR PFO INTERRUPT GND MAX708R/S/T PFO DIP/SO MR 1 8 RESET VCC 2 7 RESET 6 N.C. 5 PFO 8 WDI 7 PFO 6 PFI 5 GND GND 3 MAX708R/S/T PFI 4 DIP/SO (RESET) RESET 1 WDO 2 MR 3 V CC 4 MAX706P/R/S/T MAX706AP/AR/ AS/AT µMAX RESET 1 8 N.C. RESET 2 7 PFO 6 PFI 5 GND MR 3 V CC 4 MAX708R/S/T µMAX ( ) ARE FOR MAX706P/AP ONLY. ______________________________________________________________________________________ 11 MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T Pin Configurations Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) CDIPS.EPS MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits 12 ______________________________________________________________________________________ +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits E Ø0.50±0.1 8 INCHES DIM A A1 A2 b H c D e E H 0.6±0.1 1 L 1 α 0.6±0.1 S BOTTOM VIEW D MIN 0.002 0.030 MAX 0.043 0.006 0.037 0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6° 0° 0.0207 BSC 8LUMAXD.EPS 4X S 8 MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95 0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0° 6° 0.5250 BSC TOP VIEW A1 A2 A c e b FRONT VIEW α L SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 8L uMAX/uSOP APPROVAL DOCUMENT CONTROL NO. 21-0036 REV. J 1 1 ______________________________________________________________________________________ 13 MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) DIM A A1 B C e E H L N E H INCHES MILLIMETERS MAX MIN 0.053 0.069 0.004 0.010 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.050 0.016 MAX MIN 1.75 1.35 0.25 0.10 0.49 0.35 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 SOICN .EPS MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits 1.27 VARIATIONS: 1 INCHES TOP VIEW DIM D D D MIN 0.189 0.337 0.386 MAX 0.197 0.344 0.394 MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC D A B e C 0∞-8∞ A1 L FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, .150" SOIC APPROVAL DOCUMENT CONTROL NO. 21-0041 14 ______________________________________________________________________________________ REV. B 1 1 +3V Voltage Monitoring, Low-Cost µP Supervisory Circuits PDIPN.EPS 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15 © 2006 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX706P/R/S/T, MAX706AP/AR/AS/AT, MAX708R/S/T Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)