19-2629; Rev 5; 3/09 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output Features The MAX6730–MAX6735 single-/dual-/triple-voltage microprocessor (µP) supervisors feature a watchdog timer and manual reset capability. The MAX6730– MAX6735 offer factory-set reset thresholds for monitoring voltages from +0.9V to +5V and an adjustable reset input for monitoring voltages down to +0.63V. The combination of these features significantly improves system reliability and accuracy when compared to separate ICs or discrete components. The active-low reset output asserts and remains asserted for the reset timeout period after all the monitored voltages exceed their respective thresholds. Multiple factoryset reset threshold combinations reduce the number of external components required. The MAX6730/MAX6731 monitor a single fixed voltage, the MAX6732/MAX6733 monitor two fixed voltages, and the MAX6734/MAX6735 monitor two fixed voltages and one adjustable voltage. All devices are offered with six minimum reset timeout periods ranging from 1.1ms to 1120ms. The MAX6730–MAX6735 feature a watchdog timer with an independent watchdog output. The watchdog timer prevents system lockup during code execution errors. A watchdog startup delay of 54s after reset asserts allows system initialization during power-up. The watchdog operates in normal mode with a 1.68s delay after initialization. The MAX6730/MAX6732/MAX6734 provide an active-low, open-drain watchdog output. The MAX6731/MAX6733/MAX6735 provide an active-low, push-pull watchdog output. ♦ VCC1 (Primary Supply) Reset Threshold Voltages from +1.575V to +4.63V Other features include a manual reset input (MAX6730/ MAX6731/MAX6734/MAX6735) and push-pull reset output (MAX6731/MAX6733/MAX6735) or open-drain reset output (MAX6730/MAX6732/MAX6734). The MAX6730– MAX6733 are offered in a tiny SOT23-6 package. The MAX6734/MAX6735 are offered in a space-saving SOT23-8 package. All devices are fully specified over the extended -40°C to +85°C temperature range. Applications Multivoltage Systems Telecom/Networking Equipment Computers/Servers Portable/Battery-Operated Equipment Industrial Equipment Printer/Fax Set-Top Boxes Typical Operating Circuit and Pin Configurations appear at end of data sheet. ♦ VCC2 (Secondary Supply) Reset Threshold Voltages from +0.79V to +3.08V ♦ Adjustable RSTIN Threshold for Monitoring Voltages Down to +0.63V (MAX6734/MAX6735 Only) ♦ Six Reset Timeout Options ♦ Watchdog Timer with Independent Watchdog Output 35s (min) Initial Watchdog Startup Period 1.12s (min) Normal Watchdog Timeout Period ♦ Manual Reset Input (MAX6730/MAX6731/MAX6734/MAX6735) ♦ Guaranteed Reset Valid down to VCC1 or VCC2 = +0.8V ♦ Push-Pull RESET or Open-Drain RESET Output ♦ Immune to Short VCC Transients ♦ Low Supply Current: 14μA (typ) at +3.6V ♦ Small 6-Pin and 8-Pin SOT23 Packages Ordering Information PART* TEMP RANGE PIN-PACKAGE MAX6730UT_D_ -T -40°C to +85°C 6 SOT23 MAX6731UT_D_ -T -40°C to +85°C 6 SOT23 MAX6732UT_ _D_ -T -40°C to +85°C 6 SOT23 MAX6733UT_ _D_ -T -40°C to +85°C 6 SOT23 MAX6734KA_ _D_ -T -40°C to +85°C 8 SOT23 MAX6735KA_ _D_ -T -40°C to +85°C 8 SOT23 *Insert the threshold level suffixes for VCC1 and VCC2 (Table 1) after “UT” or “KA.” For the MAX6730/MAX6731, insert only the VCC1 threshold suffix after the “UT.” Insert the reset timeout delay (Table 2) after “D” to complete the part number. For example, the MAX6732UTLTD3-T provides a VCC1 threshold of +4.625V, a VCC2 threshold of +3.075V, and a 210ms reset timeout period. Sample stock is generally held on standard versions only (see the Standard Versions table). Standard versions have an order increment requirement of 2500 pieces. Nonstandard versions have an order increment requirement of 10,000 pieces. Contact factory for availability. Devices are available in both leaded and lead(Pb)-free/RoHScompliant packaging. Specify lead-free by replacing “-T” with “+T” when ordering. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX6730–MAX6735 General Description MAX6730–MAX6735 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output ABSOLUTE MAXIMUM RATINGS VCC1, VCC2, RSTIN, MR, WDI to GND .....................-0.3V to +6V RST, WDO to GND (open drain)...............................-0.3V to +6V RST, WDO to GND (push-pull) .................-0.3V to (VCC1 + 0.3V) Input Current/Output Current (all pins) ...............................20mA Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23-6 (derate 8.7mW/°C above +70°C) ........696mW 8-Pin SOT23-8 (derate 8.9mW/°C above +70°C) ........714mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C 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 (VCC1 = VCC2 = +0.8V to +5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Supply Voltage SYMBOL CONDITIONS VCC1, VCC2 ICC1 MIN TYP 0.8 MAX UNITS 5.5 V VCC1 < +5.5V, all I/O connections open, outputs not asserted 15 39 VCC1 < +3.6V, all I/O connections open, outputs not asserted 10 28 µA Supply Current ICC2 VCC2 < +3.6V, all I/O connections open, outputs not asserted 4 11 VCC2 < +2.75V, all I/O connections open, outputs not asserted 3 9 4.625 4.750 L (falling) VCC1 Reset Threshold 2 VTH1 4.500 M (falling) 4.250 4.375 4.500 T (falling) 3.000 3.075 3.150 S (falling) 2.850 2.925 3.000 R (falling) 2.550 2.625 2.700 Z (falling) 2.250 2.313 2.375 Y (falling) 2.125 2.188 2.250 W (falling) 1.620 1.665 1.710 V (falling) 1.530 1.575 1.620 _______________________________________________________________________________________ V Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output MAX6730–MAX6735 ELECTRICAL CHARACTERISTICS (continued) (VCC1 = VCC2 = +0.8V to +5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER VCC2 Reset Threshold SYMBOL VTH2 CONDITIONS MIN TYP MAX T (falling) 3.000 3.075 3.150 S (falling) 2.850 2.925 3.000 R (falling) 2.550 2.625 2.700 Z (falling) 2.250 2.313 2.375 Y (falling) 2.125 2.188 2.250 W (falling) 1.620 1.665 1.710 V (falling) 1.530 1.575 1.620 I (falling) 1.350 1.388 1.425 H (falling) 1.275 1.313 1.350 G (falling) 1.080 1.110 1.140 F (falling) 1.020 1.050 1.080 E (falling) 0.810 0.833 0.855 D (falling) 0.765 0.788 0.810 Reset Threshold Tempco Reset Threshold Hysteresis VCC_ to RST Output Delay Reset Timeout Period UNITS V 20 ppm/oC VHYST Referenced to VTH typical 0.5 % tRD VCC1 = (VTH1 + 100mV) to (VTH1 - 100mV) or VCC2 = (VTH2 + 75mV) to (VTH2 - 75mV) 45 µs tRP D1 1.1 1.65 2.2 D2 8.8 13.2 17.6 D3 140 210 280 D5 280 420 560 D6 560 840 1120 D4 1120 1680 2240 626.5 ms ADJUSTABLE RESET COMPARATOR INPUT (MAX6734/MAX6735) RSTIN Input Threshold VRSTIN 611 RSTIN Input Current IRSTIN -25 RSTIN Hysteresis RSTIN to Reset Output Delay tRSTIND VRSTIN to (VRSTIN - 30mV) 642 mV +25 nA 3 mV 22 µs MANUAL RESET INPUT (MAX6730/MAX6731/MAX6734/MAX6735) 0.3 × VCC1 VIL MR Input Threshold VIH MR Minimum Pulse Width 0.7 × VCC1 1 MR Glitch Rejection µs 100 MR to Reset Output Delay MR Pullup Resistance tMR ns 200 25 V 50 ns 80 kΩ _______________________________________________________________________________________ 3 MAX6730–MAX6735 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output ELECTRICAL CHARACTERISTICS (continued) (VCC1 = VCC2 = +0.8V to +5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 35 54 72 1.12 1.68 2.24 UNITS WATCHDOG INPUT Watchdog Timeout Period WDI Pulse Width WDI Input Voltage WDI Input Current tWD-L First watchdog period after reset timeout period tWD-S Normal mode tWDI (Note 2) 50 0.7 × VCC1 VIH IWDI ns 0.3 × VCC1 VIL WDI = 0 or VCC1 s -1 +1 V µA RESET/WATCHDOG OUTPUT RST / WDO Output Low Voltage (Push-Pull or Open Drain) RST / WDO Output High Voltage (Push-Pull Only) RST / WDO Output Open-Drain Leakage Current VOL VOH VCC1 or VCC2 ≥ +0.8V, ISINK = 1µA, output asserted 0.3 VCC1 or VCC2 ≥ +1.0V, ISINK = 50µA, output asserted 0.3 VCC1 or VCC2 ≥ +1.2V, ISINK = 100µA, output asserted 0.3 VCC1 or VCC2 ≥ +2.7V, ISINK = 1.2mA, output asserted 0.3 VCC1 or VCC2 ≥ +4.5V, ISINK = 3.2mA, output asserted 0.4 VCC1 ≥ +1.8V, ISOURCE = 200µA, output not asserted 0.8 × VCC1 VCC1 ≥ +2.7V, ISOURCE = 500µA, output not asserted 0.8 × VCC1 VCC1 ≥ +4.5V, ISOURCE = 800µA, output not asserted 0.8 × VCC1 Output not asserted V 0.5 Note 1: Devices tested at TA = +25°C. Overtemperature limits are guaranteed by design and not production tested. Note 2: Parameter guaranteed by design. 4 _______________________________________________________________________________________ V µA Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output ICC1 12 10 8 6 14 TOTAL 12 10 8 ICC1 6 4 2 18 16 10 35 60 85 TOTAL 10 8 ICC1 6 ICC2 0 -40 -15 10 TEMPERATURE (°C) 35 60 -40 85 -15 SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +1.8V, VCC2 = +1.2V) 14 12 10 TOTAL 8 6 ICC1 4 2 60 85 ICC2 1.010 MAX6730-35 toc05 16 35 NORMALIZED THRESHOLD VOLTAGE vs. TEMPERATURE NORMALIZED THRESHOLD VOLTAGE 18 10 TEMPERATURE (°C) TEMPERATURE (°C) MAX6730-35 toc04 -15 12 2 0 -40 14 4 ICC2 2 0 MAX6730-35 toc03 16 ICC2 4 MAX6730-35 toc02 TOTAL 14 SUPPLY CURRENT (μA) SUPPLY CURRENT (μA) 16 18 SUPPLY CURRENT (μA) MAX6730-35 toc01 18 SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +2.5V, VCC2 = +1.8V) SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +3.3V, VCC2 = +2.5V) SUPPLY CURRENT (μA) SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +5V, VCC2 = +3.3V) 1.008 1.006 1.004 1.002 1.000 0.998 0.996 0.994 0.992 0.990 0 -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX6730–MAX6735 Typical Operating Characteristics (VCC1 = +5V, VCC2 = +3.3V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC1 = +5V, VCC2 = +3.3V, TA = +25°C, unless otherwise noted.) MAXIMUM VCC_ TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE NORMALIZED TIMEOUT PERIOD vs. TEMPERATURE 1.0030 1.0025 1.0020 1.0015 1.0010 1.0005 1.0000 0.9995 0.9990 MAX6730-35 toc07 1.0035 RST ASSERTS ABOVE THIS LINE 1000 MR 2V/div 100 RST 2V/div 10 -40 -15 10 35 60 85 1 TEMPERATURE (°C) 10 100 1000 RESET THRESHOLD OVERDRIVE (mV) 70 65 60 55 50 45 MAX6730-35 toc10 75 30 RSTIN TO RESET OUTPUT DELAY (μs) MAX6730-35 toc09 VCC_ TO RESET OUTPUT DELAY (μs) 80 40ns/div RSTIN TO RESET OUTPUT DELAY vs. TEMPERATURE VCC_ TO RESET OUTPUT DELAY vs. TEMPERATURE (100mV OVERDRIVE) 28 26 24 22 20 18 16 14 12 10 40 -45 -15 10 35 TEMPERATURE (°C) 6 MR TO RESET OUTPUT DELAY MAX6730-35 toc08 10,000 MAXIMUM VCC_ TRANSIENT DURATION (μs) MAX6730-35 toc06 1.0040 NORMALIZED TIMEOUT PERIOD MAX6730–MAX6735 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output 60 85 -45 -15 10 35 60 TEMPERATURE (°C) _______________________________________________________________________________________ 85 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output PIN MAX6730 MAX6731 MAX6732 MAX6733 MAX6734 NAME MAX6735 FUNCTION Active-Low Reset Output. The MAX6730/MAX6732/MAX6734 provide an opendrain output. The MAX6731/MAX6733/MAX6735 provide a push-pull output. RST asserts low when any of the following conditions occur: VCC1 or VCC2 drops below its preset threshold, RSTIN drops below its reset threshold, or MR is driven low. Open-drain versions require an external pullup resistor. 1 1 1 RST 2 2 2 GND Ground WDO Active-Low Watchdog Output. The MAX6730/MAX6732/MAX6734 provide an open-drain WDO output. The MAX6731/MAX6733/MAX6735 provide a push-pull WDO output. WDO asserts low when no low-to-high or high-to-low transition occurs on WDI within the watchdog timeout period (tWD) or if an undervoltage lockout condition exists for VCC1, VCC2, or RSTIN. WDO deasserts without a timeout period when VCC1, VCC2, and RSTIN exceed their reset thresholds, or when the manual reset input is asserted. Open-drain versions require an external pullup resistor. MR Active-Low Manual Reset Input. Drive MR low to force a reset. RST remains asserted as long as MR is low and for the reset timeout period after MR releases high. MR has a 50k pullup resistor to VCC1; leave MR open or connect to VCC1 if unused. 3 4 3 — 4 5 5 5 3 WDI Watchdog Input. If WDI remains high or low for longer than the watchdog timeout period, the internal watchdog timer expires and the watchdog output asserts low. The internal watchdog timer clears whenever RST asserts or a rising or falling edge on WDI is detected. The watchdog has an initial watchdog timeout period (35s min) after each reset event and a short timeout period (1.12s min) after the first valid WDI transition. Floating WDI does not disable the watchdog timer function. 6 6 8 VCC1 Primary Supply-Voltage Input. VCC1 provides power to the device when it is greater than VCC2. VCC1 is the input to the primary reset threshold monitor. — 4 6 VCC2 Secondary Supply-Voltage Input. VCC2 provides power to the device when it is greater than VCC1. VCC2 is the input to the secondary reset threshold monitor. 7 Undervoltage Reset Comparator Input. RSTIN provides a high-impedance comparator input for the adjustable reset monitor. RST asserts low if the voltage RSTIN at RSTIN drops below the 626mV internal reference voltage. Connect a resistive voltage-divider to RSTIN to monitor voltages higher than 626mV. Connect RSTIN to VCC1 or VCC2 if unused. — — _______________________________________________________________________________________ 7 MAX6730–MAX6735 Pin Description MAX6730–MAX6735 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output Table 1. Reset Voltage Threshold Suffix Guide** PART NO. SUFFIX LT MS MR TZ SY RY TW SV RV TI SH RH TG SF RF TE SD RD ZW YV ZI YH ZG YF ZE YD WI VH WG VF WE VD VCC1 NOMINAL VOLTAGE THRESHOLD(V) 4.625 4.375 4.375 3.075 2.925 2.625 3.075 2.925 2.625 3.075 2.925 2.625 3.075 2.925 2.625 3.075 2.925 2.625 2.313 2.188 2.313 2.188 2.313 2.188 2.313 2.188 1.665 1.575 1.665 1.575 1.665 1.575 VCC2 NOMINAL VOLTAGE THRESHOLD (V) 3.075 2.925 2.625 2.313 2.188 2.188 1.665 1.575 1.575 1.388 1.313 1.313 1.110 1.050 1.050 0.833 0.788 0.788 1.665 1.575 1.388 1.313 1.110 1.050 0.833 0.788 1.388 1.313 1.110 1.050 0.833 0.788 **Standard versions are shown in bold and are available in a D3 timeout option only. Standard versions require 2500-piece order increments and are typically held in sample stock. There is a 10,000-piece order increment on nonstandard versions. Other threshold voltages may be available; contact factory for availability. 8 Table 2. Reset Timeout Period Suffix Guide ACTIVE TIMEOUT PERIOD TIMEOUT PERIOD SUFFIX MIN (ms) MAX (ms) D1 1.1 2.2 D2 8.8 17.6 D3 140 280 D5 280 560 D6 560 1120 D4 1120 2240 Detailed Description Supply Voltages The MAX6730–MAX6735 microprocessor (µP) supervisors maintain system integrity by alerting the µP to fault conditions. The MAX6730–MAX6735 monitor one to three supply voltages in µP-based systems and assert an active-low reset output when any monitored supply voltage drops below its preset threshold. The output state remains valid for VCC1 or VCC2 greater than +0.8V. Threshold Levels The two-letter code in the Reset Voltage Threshold Suffix Guide (Table 1) indicates the threshold level combinations for VCC1 and VCC2. Reset Output The MAX6730–MAX6735 feature an active-low reset output (RST). RST asserts when the voltage at either VCC1 or VCC2 falls below the voltage threshold level, VRSTIN drops below its threshold, or MR is driven low (Figure 1). RST remains low for the reset timeout period (Table 2) after V CC 1, V CC 2, and RSTIN increase above their respective thresholds and after MR releases high. Whenever VCC1, VCC2, or RSTIN go below the reset threshold before the end of the reset timeout period, the internal timer restarts. The MAX6730/MAX6732/ MAX6734 provide an open-drain RST output, and the MAX6731/ MAX6733/MAX6735 provide a push-pull RST output. _______________________________________________________________________________________ Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output Adjustable Input Voltage (RSTIN) MAX6730–MAX6735 Manual Reset Input Many µP-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. A logic low on MR asserts the reset output, clears the watchdog timer, and deasserts the watchdog output. Reset remains asserted while MR is low and for the reset timeout period (tRP) after MR returns high. An internal 50kΩ pullup resistor allows MR to be left open if unused. Drive MR with TTL or CMOS-logic levels or with open-drain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manual reset function; external debounce circuitry is not required. Connect a 0.1µF capacitor from MR to GND to provide additional noise immunity when driving MR over long cables or if the device is used in a noisy environment. VEXT_TH R1 MAX6734 MAX6735 RSTIN R2 GND Figure 2. Monitoring a Third Voltage The MAX6734/MAX6735 provide an additional highimpedance comparator input with a 626mV threshold to monitor a third supply voltage. To monitor a voltage higher than 626mV, connect a resistive-divider to the circuit as shown in Figure 2 to establish an externally controlled threshold voltage, VEXT_TH. VEXT_TH = 626mV × VCC1, VCC2 RSTIN RST VCC (MIN) (R1 + R2) R2 VTH tRP tRP WDO MR Figure 1. RST, WDO, and MR Timing Diagram _______________________________________________________________________________________ 9 MAX6730–MAX6735 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output The RSTIN comparator derives power from VCC1, and the input voltage must remain less than or equal to VCC1. Low leakage current at RSTIN allows the use of large-valued resistors, resulting in reduced power consumption of the system. Watchdog The watchdog feature monitors µP activity through the watchdog input (WDI). A rising or falling edge on WDI within the watchdog timeout period (tWD) indicates normal µP operation. WDO asserts low if WDI remains high or low for longer than the watchdog timeout period. Floating WDI does not disable the watchdog timer. The MAX6730–MAX6735 include a dual-mode watchdog timer to monitor µP activity. The flexible timeout architecture provides a long-period initial watchdog mode, allowing complicated systems to complete lengthy boots, and a short-period normal watchdog mode, allowing the supervisor to provide quick alerts when processor activity fails. After each reset event (VCC power-up, brownout, or manual reset), there is a long initial watchdog period of 35s (min). The long watchdog period mode provides an extended time for the system to power up and fully initialize all µP and system components before assuming responsibility for routine watchdog updates. VCC1, VCC2 RSTIN RST VCC (MIN) The usual watchdog timeout period (1.12s min) begins after the initial watchdog timeout period (tWD-L) expires or after the first transition on WDI (Figure 3). During normal operating mode, the supervisor asserts the WDO output if the µP does not update the WDI with a valid transition (high to low or low to high) within the standard timeout period (tWD-S) (1.12s min). Connect MR to WDO to force a system reset in the event that no rising or falling edge is detected at WDI within the watchdog timeout period. WDO asserts low when no edge is detected by WDI, the RST output asserts low, the watchdog counter immediately clears, and WDO returns high. The watchdog counter restarts, using the long watchdog period, when the reset timeout period ends (Figure 4). Ensuring a Valid RESET Output Down to VCC = 0 The MAX6730–MAX6735 guarantee proper operation down to VCC = +0.8V. In applications that require valid reset levels down to VCC = 0, use a 100kΩ pulldown resistor from RST to GND. The resistor value used is not critical, but it must be large enough not to load the reset output when VCC is above the reset threshold. For most applications, 100kΩ is adequate. Note that this configuration does not work for the open-drain outputs of MAX6730/MAX6732/MAX6734. VTH tRP WDO WDI < tWD-L < tWD-S < tWD-S > tWD-S < tWD-S tWD-S Figure 3. Watchdog Input/Output Timing Diagram (MR and WDO Not Connected) 10 ______________________________________________________________________________________ < tWD-S Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output RST VCC (MIN) MAX6730–MAX6735 VCC1, VCC2 RSTIN VTH tRP tRP WDO WDI < tWD-L < tWD-S > tWD-S < tWD-L MR tMR Figure 4. Watchdog Input/Output Timing Diagram (MR and WDO Connected) Applications Information Interfacing to µPs with Bidirectional Reset Pins Microprocessors with bidirectional reset pins can interface directly with the open-drain RST output options. However, conditions might occur in which the push-pull output versions experience logic contention with the bidirectional reset pin of the µP. Connect a 10kΩ resistor between RST and the µP’s reset I/O port to prevent logic contention (Figure 5). Falling VCC Transients The MAX6730–MAX6735 µP supervisors are relatively immune to short-duration falling VCC_ transients (glitches). Small glitches on V CC _ are ignored by the MAX6730–MAX6735, preventing undesirable reset pulses to the µP. The Typical Operating Characteristics show Maximum Transient Duration vs. Reset Threshold VCC2 VCC1 RESET TO OTHER SYSTEM COMPONENTS VCC1 MAX6731 MAX6733 RST MAX6735 μP 10kΩ RESET VCC2 GND GND Figure 5. Interfacing to µPs with Bidirectional Reset I/O ______________________________________________________________________________________ 11 MAX6730–MAX6735 Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output Functional Diagram Overdrive, for which reset pulses are not generated. The graph was produced using falling VCC_ pulses, starting above VTH and ending below the reset threshold by the magnitude indicated (reset threshold overdrive). The graph shows the maximum pulse width that a falling V CC transient typically might have without causing a reset pulse to be issued. As the amplitude of the transient increases (i.e., goes further below the reset threshold), the maximum allowable pulse width decreases. A 0.1µF bypass capacitor mounted close to VCC_ provides additional transient immunity. Watchdog Software Considerations 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 helps the watchdog timer closely monitor software execution. This technique avoids a “stuck” loop, in which the watchdog timer continues to be reset within the loop, preventing the watchdog from timing out. Figure 6 shows an example flow diagram in which the I/O driving the watchdog input is set high at the beginning of the program, set low at the beginning of every subroutine or loop, and then set high again when the program returns to the beginning. If the program “hangs” in any subroutine, the I/O continually asserts low (or high), and the watchdog timer expires, issuing a reset or interrupt. VCC1 MR VCC1 MAX6730– MAX6735 VCC1 VCC2 RESET TIMEOUT PERIOD VCC2 RESET OUTPUT DRIVER RST VCC1 WATCHDOG TIMER RSTIN WDO WDI VCC1 REF VREF / 2 GND SET WDI HIGH PROGRAM CODE SUBROUTINE OR PROGRAM LOOP SET WDI LOW HANG IN SUBROUTINE RETURN Figure 6. Watchdog Flow Diagram 12 VCC1 VREF START SUBROUTINE COMPLETED MR PULLUP ______________________________________________________________________________________ Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output PART TOP MARK PART TOP MARK MAX6730UTLD3-T ABCC MAX6733UTZGD3-T ABQI MAX6730UTSD3-T ABPB MAX6733UTYDD3-T ABQG MAX6730UTRD3-T ABPA MAX6733UTVHD3-T ABQE MAX6730UTZD3-T ABPD MAX6733UTWGD3-T ABQF MAX6730UTVD3-T ABPC MAX6733UTVDD3-T ABQD MAX6731UTLD3-T ABPE MAX6734KALTD3-T AEHN MAX6731UTTD3-T ABCD MAX6734KASYD3-T AEHS MAX6731UTSD3-T ABPG MAX6734KASVD3-T AEHR MAX6731UTRD3-T ABPF MAX6734KARVD3-T AEHO MAX6731UTZD3-T ABPI MAX6734KASHD3-T AEHQ MAX6731UTVD3-T ABPH MAX6734KATGD3-T AEHT MAX6732UTLTD3-T ABCE MAX6734KASDD3-T AEHP MAX6732UTSYD3-T ABPN MAX6734KAZWD3-T AEIA MAX6732UTSVD3-T ABPM MAX6734KAYHD3-T AEHY MAX6732UTRVD3-T ABPJ MAX6734KAZGD3-T AEHZ MAX6732UTSHD3-T ABPL MAX6734KAYDD3-T AEHX MAX6732UTTGD3-T ABPO MAX6734KAVHD3-T AEHV MAX6732UTSDD3-T ABPK MAX6734KAWGD3-T AEHW MAX6732UTZWD3-T ABPV MAX6734KAVDD3-T AEHU MAX6732UTYHD3-T ABPT MAX6735KALTD3-T AEIB MAX6732UTZGD3-T ABPU MAX6735KASYD3-T AEIG MAX6732UTYDD3-T ABPS MAX6735KASVD3-T AEIF MAX6732UTVHD3-T ABPQ MAX6735KARVD3-T AEIC MAX6732UTWGD3-T ABPR MAX6735KASHD3-T AEIE MAX6732UTVDD3-T ABPP MAX6735KATGD3-T AEIH MAX6733UTLTD3-T ABPW MAX6735KASDD3-T AEID MAX6733UTSYD3-T ABQB MAX6735KAZWD3-T AEIO MAX6733UTSVD3-T ABQA MAX6735KAZID3-T AAJZ MAX6733UTRVD3-T ABPX MAX6735KAYHD3-T AEIM MAX6733UTSHD3-T ABPZ MAX6735KAZGD3-T AEIN MAX6733UTTGD3-T ABQC MAX6735KAYDD3-T AEIL MAX6733UTSDD3-T ABPY MAX6735KAVHD3-T AEIJ MAX6733UTZWD3-T ABQJ MAX6735KAWGD3-T AEIK MAX6733UTYHD3-T ABQH MAX6735KAVDD3-T AEII Note: Sample stock is generally held on standard versions only. Standard versions have an order increment requirement of 2500 pieces. Nonstandard versions have an order increment requirement of 10,000 pieces. Contact factory for availability of nonstandard versions. ______________________________________________________________________________________ 13 MAX6730–MAX6735 Standard Versions Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output MAX6730–MAX6735 Pin Configurations TOP VIEW RST 1 6 MAX6730 MAX6731 GND 2 WDO 3 VCC1 RST 1 5 WDI GND 2 4 MR WDO 3 SOT23-6 6 MAX6732 MAX6733 5 WDI 4 VCC2 RST 1 GND 2 WDI +1.8V 3 MAX6734 MAX6735 WDO 4 SOT23-6 Typical Operating Circuit +0.9V VCORE VCC1 8 VCC1 7 RSTIN 6 VCC2 5 MR SOT23-8 ___________________Chip Information TRANSISTOR COUNT: 1073 PROCESS: BiCMOS +3.3V Package Information VCC2 VCC1 RSTIN RST VCC (I/O) VDD (MEMORY) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. RESET PACKAGE TYPE MAX6734 WDI MAX6735 PUSHBUTTON SWITCH WDO I/O μP PACKAGE CODE DOCUMENT NO. 6 Pin SOT23 U6-1 21-0058 8-Pin SOT23 K85N-1 21-0078 NMI MR GND GND Selector Guide 14 PART NUMBER VOLTAGE MONITORS RST OUTPUT MANUAL RESET WATCHDOG INPUT WATCHDOG OUTPUT MAX6730 1 Open Drain √ √ Open Drain MAX6731 1 Push-Pull √ √ Push-Pull MAX6732 2 Open Drain — √ Open Drain MAX6733 2 Push-Pull — √ Push-Pull MAX6734 3 Open Drain √ √ Open Drain MAX6735 3 Push-Pull √ √ Push-Pull ______________________________________________________________________________________ Single-/Dual-/Triple-Voltage µP Supervisory Circuits with Independent Watchdog Output PAGES CHANGED REVISION NUMBER REVISION DATE 0 10/02 Initial release. — 1 12/02 Released MAX6730/MAX6731. 1 2 1/03 Released MAX6733. 1 3 3/04 Updated Typical Operating Circuit. 14 4 12/05 Added lead-free notation to Ordering Information. 1 5 3/09 DESCRIPTION Updated Pin Description and added Package Table. 7, 14 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 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX6730–MAX6735 Revision History