19-0496; Rev 4; 11/99 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset ____________________________Features ♦ Small 5-Pin SOT23 Package ♦ Available in 26 Reset Threshold Voltages 2.5V to 5V, in 100mV Increments ♦ Four Reset Timeout Periods 1ms, 20ms, 140ms, or 1.12s (min) ♦ Four Watchdog Timeout Periods 6.3ms, 102ms, 1.6s, or 25.6s (typ) ♦ Four Reset Output Stages Active-High, Push/Pull Active-Low, Push/Pull Active-Low, Open-Drain Active-Low, Bidirectional ♦ Guaranteed Reset Valid to VCC = 1V ♦ Immune to Short Negative VCC Transients ♦ Low Cost ♦ No External Components _______________Ordering Information The MAX6316–MAX6322 are offered in a miniature 5-pin SOT23 package. PART TEMP. RANGE PIN-PACKAGE -40°C to +85°C 5 SOT23-5 MAX6316MUK____-T -40°C to +85°C 5 SOT23-5 MAX6317HUK____-T -40°C to +85°C 5 SOT23-5 MAX6318HUK____-T -40°C to +85°C 5 SOT23-5 MAX6318MHUK____-T -40°C to +85°C 5 SOT23-5 MAX6316LUK____-T ________________________Applications Portable Computers Computers Controllers Intelligent Instruments Portable/Battery-Powered Equipment Embedded Control Systems Ordering Information continued at end of data sheet. Typical Operating Circuit and Pin Configurations appear at end of data sheet. ___________________________________________________________________Selector Guide RESET OUTPUTS* WATCHDOG INPUT MANUAL RESET INPUT ACTIVE-LOW PUSH/PULL ACTIVE-HIGH PUSH/PULL ACTIVE-LOW BIDIRECTIONAL ACTIVE-LOW OPEN-DRAIN MAX6316L ✔ ✔ ✔ — MAX6316M ✔ — MAX6317H ✔ ✔ — — MAX6318LH ✔ — — ✔ — ✔ — ✔ — ✔ — MAX6318MH ✔ — — ✔ ✔ MAX6319LH — ✔ — ✔ — MAX6319MH ✔ — ✔ MAX6320P — ✔ — ✔ ✔ — — MAX6321HP ✔ — — ✔ MAX6322HP — — ✔ — ✔ — ✔ — ✔ — ✔ PART ✔ ✔ — — * The MAX6318/MAX6319/MAX6321/MAX6322 feature two types of reset output on each device. ________________________________________________________________ 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 MAX6316–MAX6322 ________________General Description The MAX6316–MAX6322 family of microprocessor (µP) supervisory circuits monitors power supplies and microprocessor activity in digital systems. It offers several combinations of push/pull, open-drain, and bidirectional (such as Motorola 68HC11) reset outputs, along with watchdog and manual reset features. The Selector Guide below lists the specific functions available from each device. These devices are specifically designed to ignore fast negative transients on VCC. Resets are guaranteed valid for VCC down to 1V. These devices are available in 26 factory-trimmed reset threshold voltages (from 2.5V to 5V, in 100mV increments), featuring four minimum power-on reset timeout periods (from 1ms to 1.12s), and four watchdog timeout periods (from 6.3ms to 25.6s). Thirteen standard versions are available with an order increment requirement of 2500 pieces (see Standard Versions table); contact the factory for availability of other versions, which have an order increment requirement of 10,000 pieces. MAX6316–MAX6322 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset ABSOLUTE MAXIMUM RATINGS Voltage (with respect to GND) VCC......................................................................-0.3V to +6V RESET (MAX6320/MAX6321/MAX6322 only)...... -0.3V to +6V All Other Pins.........................................-0.3V to (VCC + 0.3V) Input/Output Current, All Pins .............................................20mA Continuous Power Dissipation (TA = +70°C) SOT23-5 (derate 7.1mW/°C above +70°C)...............571mW Operating Temperature Range............................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range..............................-65°C to +160°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 (VCC = 2.5V to 5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Operating Voltage Range Supply Current Reset Threshold Temperature Coefficient Reset Threshold (Note 2) SYMBOL CONDITIONS MIN 1 VCC to RESET Delay MAX UNITS 5.5 V VCC TA = -40°C to +85°C VCC = 5.5V ICC MAX6316/MAX6317/MAX6318/ MAX6320/MAX6321: MR and WDI unconnected VCC = 3.6V 5 12 MAX6319/MAX6322: MR unconnected VCC = 5.5V 5 12 VCC = 3.6V 3 8 10 ∆VTH/°C VRST 20 40 VTH -1.5% VTH VTH +1.5% TA = -40°C to +85°C VTH -2.5% VTH VTH +2.5% 3 tRP tRD V mV MAX63_ _A_-T 1 1.4 2 MAX63_ _B_-T 20 28 40 MAX63_ _C_-T 140 200 280 MAX63_ _D_-T 1120 1600 2240 VCC falling at 1mV/µs µA ppm/°C TA = +25°C Reset Threshold Hysteresis Reset Active Timeout Period TYP 40 ms µs PUSH/PULL RESET OUTPUT (MAX6316L/MAX6317H/MAX6318_H/MAX6319_H/MAX6321HP/MAX6322HP) VOL RESET Output Voltage VOH VOL RESET Output Voltage VOH VCC ≥ 1.0V, ISINK = 50µA 0.3 VCC ≥ 1.2V, ISINK = 100µA 0.3 VCC ≥ 2.7V, ISINK = 1.2mA 0.3 VCC ≥ 4.5V, ISINK = 3.2mA 0.4 VCC ≥ 2.7V, ISOURCE = 500µA 0.8 x VCC VCC ≥ 4.5V, ISOURCE = 800µA VCC - 1.5 VCC ≥ 2.7V, ISINK = 1.2mA 0.3 VCC ≥ 4.5V, ISINK = 3.2mA 0.4 VCC ≥ 1.8V, ISOURCE = 150µA 0.8 x VCC VCC ≥ 2.7V, ISOURCE = 500µA 0.8 x VCC VCC ≥ 4.5V, ISOURCE = 800µA VCC - 1.5 Note 1: Over-temperature limits are guaranteed by design, not production tested. Note 2: A factory-trimmed voltage divider programs the nominal reset threshold (VTH). Factory-trimmed reset thresholds are available in 100mV increments from 2.5V to 5V (see Table 1 at end of data sheet). 2 _______________________________________________________________________________________ V V 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset (VCC = 2.5V 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 BIDIRECTIONAL RESET OUTPUT (MAX6316M/MAX6318MH/MAX6319MH) Transition Flip-Flop Setup Time tS (Note 3) RESET Output Rise Time (Note 4) tR TYP 400 VPTH 333 VCC = 5.0V, CL = 200pF 333 VCC = 3.0V, CL = 250pF 666 RESET Active Pullup Current VCC = 5.0V 0.65 4.2 4.7 Open-Drain Reset Output Leakage Current VOL V 20 OPEN-DRAIN RESET OUTPUT (MAX6320P/MAX6321HP/MAX6322HP) VCC ≥ 1.0V, ISINK = 50µA RESET Output Voltage ns 666 0.4 VCC = 5.0V RESET Pullup Resistance UNITS ns VCC = 3.0V, CL = 120pF VCC = 5.0V, CL = 400pF Active Pullup Enable Threshold MAX mA 5.2 kΩ 0.3 VCC ≥ 1.2V, ISINK = 100µA 0.3 VCC ≥ 2.7V, ISINK = 1.2mA 0.3 VCC ≥ 4.5V, ISINK = 3.2mA 0.4 ILKG 1.0 V µA WATCHDOG INPUT (MAX6316/MAX6317H/MAX6318_H/MAX6320P/MAX6321HP) Watchdog Timeout Period WDI Pulse Width tWD tWDI WDI Input Threshold WDI Input Current (Note 6) VIL VIH IWDI MAX63_ _ _ W-T 4.3 6.3 9.3 MAX63_ _ _ X-T 71 102 153 MAX63_ _ _ Y-T 1.12 1.6 2.4 MAX63_ _ _ Z-T 17.9 25.6 38.4 VIL = 0.3 x VCC, VIH = 0.7 x VCC (Note 5) 50 VWDI = 0, time average 0.7 x VCC 120 -20 s ns 0.3 x VCC WDI = VCC, time average ms 160 -15 V µA MANUAL RESET INPUT (MAX6316_/MAX6317H/MAX6319_H/MAX6320P/MAX6322HP) VIL MR Input Threshold VIH VIL VIH VTH > 4.0V VTH < 4.0V MR Input Pulse Width 0.8 2.0 0.3 x VCC 0.7 x VCC 1 MR Glitch Rejection MR to Reset Delay Note 3: Note 4: Note 5: Note 6: µs 100 MR Pullup Resistance 35 VCC = 5V V 52 230 ns 75 kΩ ns This is the minimum time RESET must be held low by an external pulldown source to set the active pullup flip-flop. Measured from RESET VOL to (0.8 x VCC), RLOAD = ∞. WDI is internally serviced within the watchdog period if WDI is left unconnected. The WDI input current is specified as the average input current when the WDI input is driven high or low. The WDI input is designed for a three-stated-output device with a 10µA maximum leakage current and capable of driving a maximum capacitive load of 200pF. The three-state device must be able to source and sink at least 200µA when active. _______________________________________________________________________________________ 3 MAX6316–MAX6322 ELECTRICAL CHARACTERISTICS (continued) __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) 8 7 6 5 VCC = 3V 4 3 2 VCC = 1V 1 VCC FALLING AT 1mV/µs VRST - VCC = 100mV 90 0 320 80 70 60 50 40 30 0 20 40 60 80 100 200 160 140 -40 -20 0 20 40 60 80 -40 100 -20 0 1.02 1.01 1.00 0.99 0.98 0.97 0.96 0.95 40 60 80 100 NORMALIZED WATCHDOG TIMEOUT PERIOD MAX6316toc04 1.03 20 40 60 80 100 MAX6316/MAX6317/MAX6318/MAX6320/MAX6321 NORMALIZED WATCHDOG TIMEOUT PERIOD vs. TEMPERATURE 1.04 0 20 TEMPERATURE (°C) TEMPERATURE (°C) 1.05 NORMALIZED RESET TIMEOUT PERIOD 220 10 NORMALIZED RESET TIMEOUT PERIOD vs. TEMPERATURE -20 240 180 TEMPERATURE (°C) -40 260 1.05 MAX6316toc05 -20 280 20 0 -40 VCC = 5V 300 PROPAGATION DELAY (ns) VCC = 5V 100 MAX6316toc02 9 RESET PROPAGATION DELAY (µs) MAX6316toc01 10 MAX6316/MAX6317/MAX6319/MAX6320/MAX6322 MANUAL RESET TO RESET PROPAGATION DELAY vs. TEMPERATURE VCC FALLING TO RESET PROPAGATION DELAY vs. TEMPERATURE MAX6316toc03 MAX6316/MAX6317/MAX6318/MAX6320/MAX6321 SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT (µA) 1.04 1.03 1.02 1.01 1.00 0.99 0.98 0.97 0.96 0.95 -40 TEMPERATURE (°C) -20 0 20 40 60 80 100 TEMPERATURE (°C) MAX6316M/6318MH/6319MH BIDIRECTIONAL PULLUP CHARACTERISTICS MAXIMUM VCC TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE MAX6316toc07 MAX6316toc06 80 RESET OCCURS ABOVE LINES 70 TRANSIENT DURATION (µs) MAX6316–MAX6322 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset VRST = 3.3V 60 +5V 74HC05 INPUT PASSIVE 4.7kΩ PULLUP 2V/div 4.7kΩ 100pF VRST = 4.63V 50 +5V 40 VRST = 2.63V INPUT 30 74HC05 100pF 20 VCC RESET MR GND 10 0 10 100 1000 200ns/div RESET THRESHOLD OVERDRIVE (mV) VRST - VCC 4 RESET, ACTIVE PULLUP 2V/div _______________________________________________________________________________________ RESET INPUT 5V/div 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset PIN MAX6316L MAX6316M MAX6320P MAX6317H MAX6318LH MAX6318MH MAX6321HP MAX6319LH MAX6319MH MAX6322HP NAME FUNCTION MAX6316L/MAX6318LH/MAX6319LH: Active-Low, Reset Output. CMOS push/pull output (sources and sinks current). 1 — 1 1 RESET MAX6316M/MAX6318MH/MAX6319MH: Bidirectional, Active-Low, Reset Output. Intended to interface directly to microprocessors with bidirectional resets such as the Motorola 68HC11. MAX6320P/MAX6321HP/MAX6322HP: Open-Drain, Active-Low, Reset Output. NMOS output (sinks current only). Connect a pullup resistor from RESET to any supply voltage up to 6V. — 1 3 3 RESET 2 2 2 2 GND 3 4 5 3 4 5 — 4 5 4 — 5 Active-High, Reset Output. CMOS push/pull output (sources and sinks current). Inverse of RESET. Ground MR Active-Low, Manual Reset Input. Pull low to force a reset. Reset remains asserted for the duration of the Reset Timeout Period after MR transitions from low to high. Leave unconnected or connected to VCC if not used. WDI Watchdog Input. Triggers a reset if it remains either high or low for the duration of the watchdog timeout period. The internal watchdog timer clears whenever a reset asserts or whenever WDI sees a rising or falling edge. To disable the watchdog feature, leave WDI unconnected or three-state the driver connected to WDI. VCC Supply Voltage. Reset is asserted when VCC drops below the Reset Threshold Voltage (VRST). Reset remains asserted until VCC rises above VRST and for the duration of the Reset Timeout Period (tRP) once VCC rises above VRST. _______________________________________________________________________________________ 5 MAX6316–MAX6322 ______________________________________________________________Pin Description MAX6316–MAX6322 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset VCC MAX6316–MAX6322 RESET (ALL EXCEPT MAX6317) RESET GENERATOR RESET (ALL EXCEPT MAX6316/MAX6320P) VCC 1.23V 52kΩ MR (ALL EXCEPT MAX6318/MAX6321) WATCHDOG TRANSITION DETECTOR WDI (ALL EXCEPT MAX6319/MAX6322) WATCHDOG TIMER 52kΩ GND Figure 1. Functional Diagram _______________Detailed Description A microprocessor’s (µP) reset input starts or restarts the µP in a known state. The reset output of the MAX6316– MAX6322 µP supervisory circuits interfaces with the reset input of the µP, preventing code-execution errors during power-up, power-down, and brownout conditions (see the Typical Operating Circuit). The MAX6316/ MAX6317/MAX6318/MAX6320/MAX6321 are also capable of asserting a reset should the µP become stuck in an infinite loop. the watchdog timeout period (tWD). Reset remains asserted for the specified reset active timeout period (tRP) after VCC rises above the reset threshold, after MR transitions low to high, or after the watchdog timer asserts the reset (MAX6316_/MAX6317H/MAX6318_H/MAX6320P/ MAX6321HP). After the reset active timeout period (tRP) expires, the reset output deasserts, and the watchdog timer restarts from zero (Figure 2). VCC Reset Output The MAX6316L/MAX6318LH/MAX6319LH feature an active-low reset output, while the MAX6317H/ MAX6318_H/MAX6319_H/MAX6321HP/MAX6322HP feature an active-high reset output. RESET is guaranteed to be a logic low and RESET is guaranteed to be a logic high for VCC down to 1V. The MAX6316–MAX6322 assert reset when VCC is below the reset threshold (V RST ), when MR is pulled low (MAX6316_/MAX6317H/MAX6319_H/MAX6320P/ MAX6322HP only), or if the WDI pin is not serviced within 6 1V VRST VRST 1V GND RESET tRP tRD RESET tRP tRD GND Figure 2. Reset Timing Diagram _______________________________________________________________________________________ 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset scratch. If, on the other hand, RESET is high after a delay of two external-clock cycles, the processor knows that it caused the reset itself and can jump to a different vector and use stored-state information to determine what caused the reset. A problem occurs with faster µPs; two external-clock cycles are only 500ns at 4MHz. When there are several devices on the reset line, and only a passive pullup resistor is used, the input capacitance and stray capacitance can prevent RESET from reaching the logic high state (0.8 ✕ VCC) in the time allowed. If this happens, all resets will be interpreted as external. The µP output stage is guaranteed to sink 1.6mA, so the rise time can not be reduced considerably by decreasing the 4.7kΩ internal pullup resistance. See Bidirectional Pullup Characteristics in the Typical Operating Characteristics. The MAX6316M/MAX6318MH/MAX6319MH overcome this problem with an active pullup FET in parallel with the 4.7kΩ resistor (Figures 4 and 5). The pullup transistor holds RESET high until the µP reset I/O or the supervisory circuit itself forces the line low. Once RESET goes below VPTH, a comparator sets the transition edge flip-flop, indicating that the next transition for RESET will be low to high. When RESET is released, the 4.7kΩ resistor pulls RESET up toward VCC. Once RESET rises above VPTH but is below (0.85 x VCC), the active P-channel pullup turns on. Once RESET rises above (0.85 x VCC) or the 2µs one-shot times out, the active pullup turns off. The parallel combination of the 4.7kΩ pullup and the VCC VCC WDI* MR** 68HC11 4.7kΩ RESET CIRCUITRY RESET RESET RESET CIRCUITRY RESET*** CIN MAX6316M MAX6318MH MAX6319MH * MAX6316M/MAX6318MH ** MAX6316M/MAX6319MH *** ACTIVE-HIGH PUSH/PULL MAX6318MH/MAX6319MH CIN CSTRAY RESET CIN OTHER DEVICES Figure 3. MAX6316M/MAX6318MH/MAX6319MH Supports Additional Devices on the Reset Bus _______________________________________________________________________________________ 7 MAX6316–MAX6322 Bidirectional RESET Output The MAX6316M/MAX6318MH/MAX6319MH are designed to interface with µPs that have bidirectional reset pins, such as the Motorola 68HC11. Like an open-drain output, these devices allow the µP or other devices to pull the bidirectional reset (RESET) low and assert a reset condition. However, unlike a standard open-drain output, it includes the commonly specified 4.7kΩ pullup resistor with a P-channel active pullup in parallel. This configuration allows the MAX6316M/MAX6318MH/ MAX6319MH to solve a problem associated with µPs that have bidirectional reset pins in systems where several devices connect to RESET (Figure 3). These µPs can often determine if a reset was asserted by an external device (i.e., the supervisor IC) or by the µP itself (due to a watchdog fault, clock error, or other source), and then jump to a vector appropriate for the source of the reset. However, if the µP does assert reset, it does not retain the information, but must determine the cause after the reset has occurred. The following procedure describes how this is done in the Motorola 68HC11. In all cases of reset, the µP pulls RESET low for about four external-clock cycles. It then releases RESET, waits for two external-clock cycles, then checks RESET’s state. If RESET is still low, the µP concludes that the source of the reset was external and, when RESET eventually reaches the high state, it jumps to the normal reset vector. In this case, storedstate information is erased and processing begins from MAX6316–MAX6322 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset VCC MAX6316M MAX6318MH MAX6319MH LASERTRIMMED RESISTORS VCC VREF 52kΩ MR RESET GENERATOR WATCHDOG ON 2µs ONE SHOT CIRCUITRY WDI VCC 2µs ONE SHOT TRANSITION FLIP-FLOP R Q 4.7kΩ FF S RESET ACTIVE PULLUP ENABLE COMPARATOR 0.85VCC 0.65V GND Figure 4. MAX6316/MAX6318MH/MAX6319MH Bidirectional Reset Output Functional Diagram 8 _______________________________________________________________________________________ (MAX6316M/ MAX6319MH) (MAX6316M/ MAX6318MH) 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset Open-Drain RESET Output The MAX6320P/MAX6321HP/MAX6322HP have an active-low, open-drain reset output. This output structure will sink current when RESET is asserted. Connect a pullup resistor from RESET to any supply voltage up to 6V (Figure 6). Select a resistor value large enough to VCC tRP OR µC RESET DELAY RESET 0.7V 0.8 x VCC tR tS RESET PULLED LOW BY µC OR RESET GENERATOR ACTIVE PULLUP TURNS ON Figure 5. Bidirectional RESET Timing Diagram +3.3V VCC 10kΩ WDI** RESET 5V SYSTEM RESET*** MAX6320 MAX6321 MAX6322 GND Manual-Reset Input The MAX6316_/MAX6317H/MAX6319_H/MAX6320P/ MAX6322HP feature a manual reset input. A logic low on MR asserts a reset. After MR transitions low to high, reset remains asserted for the duration of the reset timeout period (tRP). The MR input is connected to VCC through an internal 52kΩ pullup resistor and therefore can be left unconnected when not in use. MR can be driven with TTL-logic levels in 5V systems, with CMOS-logic levels in 3V systems, or with open-drain or open-collector output devices. A normally-open momentary switch from MR to ground can also be used; it requires no external debouncing circuitry. MR is designed to reject fast, negative-going transients (typically 100ns pulses). A 0.1µF capacitor from MR to ground provides additional noise immunity. The MR input pin is equipped with internal ESD-protection circuitry that may become forward biased. Should MR be driven by voltages higher than VCC, excessive current would be drawn, which would damage the part. For example, assume that MR is driven by a +5V supply other than VCC. If VCC drops lower than +4.7V, MR’s absolute maximum rating is violated [-0.3V to (VCC + 0.3V)], and undesirable current flows through the ESD structure from MR to VCC. To avoid this, use the same supply for MR as the supply monitored by VCC. This guarantees that the voltage at MR will never exceed VCC. Watchdog Input +5.0V MR* register a logic low (see Electrical Characteristics), and small enough to register a logic high while supplying all input current and leakage paths connected to the RESET line. A 10kΩ pullup is sufficient in most applications. * MAX6320/MAX6322 ** MAX6320/MAX6321 *** MAX6321/MAX6322 Figure 6. MAX6320P/MAX6321HP/MAX6322HP Open-Drain RESET Output Allows Use with Multiple Supplies The MAX6316_/MAX6317H/MAX6318_H/MAX6320P/ MAX6321HP feature a watchdog circuit that monitors the µP’s activity. If the µP does not toggle the watchdog input (WDI) within the watchdog timeout period (tWD), reset asserts. The internal watchdog timer is cleared by reset or by a transition at WDI (which can detect pulses as short as 50ns). The watchdog timer remains cleared while reset is asserted. Once reset is released, the timer begins counting again (Figure 7). The WDI input is designed for a three-stated output device with a 10µA maximum leakage current and the capability of driving a maximum capacitive load of 200pF. The three-state device must be able to source and sink at least 200µA when active. Disable the watchdog function by leaving WDI unconnected or by three-stating the driver connected to WDI. When the watchdog timer is left open circuited, the timer is cleared internally at intervals equal to 7/8 of the watchdog period. _______________________________________________________________________________________ 9 MAX6316–MAX6322 P-channel transistor on-resistance quickly charges stray capacitance on the reset line, allowing RESET to transition from low to high within the required two electronic-clock cycles, even with several devices on the reset line. This process occurs regardless of whether the reset was caused by VCC dipping below the reset threshold, the watchdog timing out, MR being asserted, or the µP or other device asserting RESET. The parts do not require an external pullup. To minimize supply current consumption, the internal 4.7kΩ pullup resistor disconnects from the supply whenever the MAX6316M/ MAX6318MH/MAX6319MH assert reset. MAX6316–MAX6322 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset VCC tRST RESET VCC tRP tWD MAX6316 MAX6318 MAX6319 tRP VCC WDI GND RESET 100kΩ MAX6316/MAX6317 MAX6318/MAX6320 MAX6321 Figure 7. Watchdog Timing Relationship Figure 8. Ensuring RESET Valid to VCC = 0 on Active-Low Push/Pull and Bidirectional Outputs Applications Information Watchdog Input Current The WDI input is internally driven through a buffer and series resistor from the watchdog counter. For minimum watchdog input current (minimum overall power consumption), leave WDI low for the majority of the watchdog timeout period. When high, WDI can draw as much as 160µA. Pulsing WDI high at a low duty cycle will reduce the effect of the large input current. When WDI is left unconnected, the watchdog timer is serviced within the watchdog timeout period by a low-high-low pulse from the counter chain. Negative-Going VCC Transients These supervisors are immune to short-duration, negative-going VCC transients (glitches), which usually do not require the entire system to shut down. Typically, 200ns large-amplitude pulses (from ground to VCC) on the supply will not cause a reset. Lower amplitude pulses result in greater immunity. Typically, a VCC transient that goes 100mV under the reset threshold and lasts less than 4µs will not trigger a reset. An optional 0.1µF bypass capacitor mounted close to VCC provides additional transient immunity. Ensuring Valid Reset Outputs Down to VCC = 0 The MAX6316_/MAX6317H/MAX6318_H/MAX6319_H/ MAX6321HP/MAX6322HP are guaranteed to operate properly down to VCC = 1V. In applications that require valid reset levels down to VCC = 0, a pulldown resistor to active-low outputs (push/pull and bidirectional only, Figure 8) and a pullup resistor to active-high outputs (push/pull only, Figure 9) will ensure that the reset line is valid while the reset output can no longer sink or 10 MAX6317 MAX6318 MAX6319 MAX6321* MAX6322* VCC GND VCC 100kΩ RESET *THIS SCHEMATIC DOES NOT WORK ON THE OPEN-DRAIN OUTPUTS OF THE MAX6321/MAX6322. Figure 9. Ensuring RESET Valid to VCC = 0 on Active-High Push/Pull Outputs source current. This scheme does not work with the open-drain outputs of the MAX6320/MAX6321/MAX6322. 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. Watchdog Software Considerations (MAX6316/MAX6317/MAX6318/ MAX6320/MAX6321) One way to help the watchdog timer monitor software execution more closely is to set and reset the watchdog input at different points in the program, rather than pulsing the watchdog input high-low-high or low-highlow. This technique avoids a stuck loop, in which the watchdog timer would continue to be reset inside the loop, keeping the watchdog from timing out. ______________________________________________________________________________________ 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset MAX6316–MAX6322 Figure 10 shows an example of a flow diagram where the I/O driving the watchdog input is set high at the beginning of the program, set low at the end of every subroutine or loop, then set high again when the program returns to the beginning. If the program should hang in any subroutine, the problem would be quickly corrected, since the I/O is continually set low and the watchdog timer is allowed to time out, causing a reset or interrupt to be issued. As described in the Watchdog Input Current section, this scheme results in higher time average WDI current than does leaving WDI low for the majority of the timeout period and periodically pulsing it low-high-low. START SET WDI HIGH PROGRAM CODE SUBROUTINE OR PROGRAM LOOP POSSIBLE INFINITE LOOP PATH SET WDI LOW RETURN Figure 10. Watchdog Flow Diagram __________________Pin Configurations Typical Operating Circuit TOP VIEW RESET 1 GND 2 5 VCC MAX6316 MAX6320 MR 3 RESET 1 GND 2 4 WDI GND 2 MAX6318 MAX6321 RESET 3 4 WDI SOT23-5 RESET RESET µP MAX6316 4 WDI RESET 1 GND 2 VCC VCC MANUAL RESET SOT23-5 5 VCC VIN MAX6317 MR 3 SOT23-5 RESET 1 5 VCC MR GND WDI I/O GND 5 VCC MAX6319 MAX6322 RESET 3 4 MR SOT23-5 ______________________________________________________________________________________ 11 MAX6316–MAX6322 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset Table 1. Factory-Trimmed Reset Thresholds PART MIN 4.925 7.827 4.728 4.630 4.561 4.433 4.314 4.236 4.137 4.039 3.940 3.842 3.743 3.645 3.546 3.448 3.349 3.251 3.152 3.034 2.955 2.886 2.758 2.660 2.591 2.463 MAX63___50_ _-T MAX63___49_ _-T MAX63___48_ _-T MAX63___47_ _-T MAX63___46_ _-T MAX63___45_ _-T MAX63___44_ _-T MAX63___43_ _-T MAX63___42_ _-T MAX63___41_ _-T MAX63___40_ _-T MAX63___39_ _-T MAX63___38_ _-T MAX63___37_ _-T MAX63___36_ _-T MAX63___35_ _-T MAX63___34_ _-T MAX63___33_ _-T MAX63___32_ _-T MAX63___31_ _-T MAX63___30_ _-T MAX63___29_ _-T MAX63___28_ _-T MAX63___27_ _-T MAX63___26_ _-T MAX63___25_ _-T TA = +25°C TYP 5.000 4.900 4.800 4.700 4.630 4.500 4.390 4.300 4.200 4.100 4.000 3.900 3.800 3.700 3.600 3.500 3.400 3.300 3.200 3.080 3.000 2.930 2.800 2.700 2.630 2.500 MAX 5.075 4.974 4.872 4.771 4.699 4.568 4.446 4.365 4.263 4.162 4.060 3.959 3.857 3.756 3.654 3.553 3.451 3.350 3.248 3.126 3.045 2.974 2.842 2.741 2.669 2.538 TA = -40°C to +85°C MIN MAX 4.875 5.125 4.778 5.023 4.680 4.920 4.583 4.818 4.514 4.746 4.388 4.613 4.270 4.490 4.193 4.408 4.095 4.305 3.998 4.203 3.900 4.100 3.803 3.998 3.705 3.895 3.608 3.793 3.510 3.690 3.413 3.588 3.315 3.485 3.218 3.383 3.120 3.280 3.003 3.157 2.925 3.075 2.857 3.000 2.730 2.870 2.633 2.768 2.564 2.696 2.438 2.563 Table 2. Standard Versions RESET THRESHOLD (V) MINIMUM RESET TIMEOUT (ms) TYPICAL WATCHDOG TIMEOUTS (s) MAX6316LUK29CY-T 2.93 140 1.6 ACDE MAX6316LUK46CY-T 4.63 140 1.6 ACDD MAX6316MUK29CY-T 2.93 140 1.6 ACDG PART 12 SOT TOP MARK MAX6316MUK46CY-T 4.63 140 1.6 ACDF MAX6317HUK46CY-T 4.63 140 1.6 ACDQ MAX6318LHUK46CY-T 4.63 140 1.6 ACDH MAX6318MHUK46CY-T 4.63 140 1.6 ACDJ MAX6319LHUK46C-T 4.63 140 — ACDK MAX6319MHUK46C-T 4.63 140 — ACDM MAX6320PUK29CY-T 2.93 140 1.6 ACDO ______________________________________________________________________________________ 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset PART RESET THRESHOLD (V) MINIMUM RESET TIMEOUT (ms) TYPICAL WATCHDOG TIMEOUTS (s) SOT TOP MARK 4.63 140 1.6 ACDN MAX6320PUK46CY-T MAX6321HPUK46CY-T 4.63 140 1.6 ACGL MAX6322HPUK46C-T 4.63 140 1.6 ACGN Note: Thirteen standard versions are available, with a required order increment of 2500 pieces. Sample stock is generally held on standard versions only. The required order increment for nonstandard versions is 10,000 pieces. Contact factory for availability. Table 3. Reset/Watchdog Timeout Periods RESET TIMEOUT PERIODS SUFFIX MIN TYP MAX A 1 1.6 2 B 20 30 40 C 140 200 280 D 1.12 1.60 2.24 UNITS ms s WATCHDOG TIMEOUT W 4.3 6.3 9.3 X 71 102 153 Y 1.12 1.6 2.4 Z 17.9 25.6 38.4 ms s __Ordering Information (continued) PART TEMP. RANGE PIN-PACKAGE MAX6319LHUK____-T -40°C to +85°C 5 SOT23-5 MAX6319MHUK____-T -40°C to +85°C 5 SOT23-5 MAX6320PUK____-T -40°C to +85°C 5 SOT23-5 MAX6321HPUK____-T -40°C to +85°C 5 SOT23-5 MAX6322HPUK____-T -40°C to +85°C 5 SOT23-5 Note: These devices are available with factory-set VCC reset thresholds from 2.5V to 5V, in 0.1V increments. Insert the desired nominal reset threshold (25 to 50, from Table 1) into the blanks following the letters UK. All devices offer factory-programmed reset timeout periods. Insert the letter corresponding to the desired reset timeout period (A, B, C, or D from Table 3) into the blank following the reset threshold suffix. Parts that offer a watchdog feature (see Selector Guide) are factory-trimmed to one of four watchdog timeout periods. Insert the letter corresponding to the desired watchdog timeout period (W, X, Y, or Z from Table 3) into the blank following the reset timeout suffix. Chip Information TRANSISTOR COUNT: 191 SUBSTRATE IS INTERNALLY CONNECTED TO V+ ______________________________________________________________________________________ 13 MAX6316–MAX6322 Table 2. Standard Versions (continued) 5-Pin µP Supervisory Circuits with Watchdog and Manual Reset SOT5L.EPS MAX6316–MAX6322 Package Information 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. 14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.