MAX824TEUK+

19-0487; Rev 5; 12/05 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset The MAX823/MAX824/MAX825* microprocessor (µP) supervisory circuits combine reset output, watchdog, and manual reset input functions in 5-pin SOT23 and SC70 packages. They significantly improve system reliability and accuracy compared to separate ICs or discrete components. The MAX823/MAX824/MAX825 are specifically designed to ignore fast transients on VCC. Seven preprogrammed reset threshold voltages are available (see Reset Threshold Table). All three devices have an active-low reset output, which is guaranteed to be in the correct state for VCC down to 1V. The MAX823 also offers a watchdog input and manual reset input. The MAX824 offers a watchdog input and a complementary active-high reset. The MAX825 offers a manual reset input and a complementary active-high reset. The Selector Guide explains the functions offered in this series of parts. Features ♦ Precision Monitoring of +2.5V, +3V, +3.3V, and +5V Power Supplies ♦ Operating Current: 6µA (MAX823L/M) (SC70) 2µA (MAX825T/S/R/Z/Y) (SC70) ♦ Fully Specified Over Temperature ♦ 140ms min Power-On Reset ♦ Guaranteed RESET Valid to VCC = 1V ♦ Power-Supply Transient Immunity ♦ Watchdog Timer with 1.6s Timeout (MAX823/MAX824) ♦ Manual Reset Input (MAX823/MAX825) ♦ No External Components Ordering Information PART† *Pg ________________________Applications Computers and Controllers Embedded Controllers Intelligent Instruments Automotive Systems Critical µP Monitoring Portable/Battery-Powered Equipment TEMP. RANGE PIN-PACKAGE MAX823_EXK-T -40°C to +85°C 5 SC70-5 MAX823_EUK-T -40°C to +125°C 5 SOT23-5 MAX824_EXK-T -40°C to +85°C 5 SC70-5 †Insert the desired suffix letter (from the Reset Threshold table) into the blank to complete the part number. All devices are available in tape-and-reel only. There is a 2500 piece minimum order increment. Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing “-T” with “+T” when ordering. Reset Threshold Table Ordering Information continued at end of data sheet. SUFFIX RESET THRESHOLD (V) L 4.63 M 4.38 T 3.08 Active-High Reset S 2.93 R 2.63 Z (SC70 only) 2.32 Y (SC70 only) 2.19 ______________________Selector Guide FUNCTION MAX823 MAX824 MAX825 ✔ ✔ ✔ ✔ Watchdog Input — ✔ ✔ ✔ Manual Reset Input ✔ — — ✔ Active-Low Reset Typical Operating Circuit appears at end of data sheet. Marking Information appears at end of data sheet. Pin Configurations TOP VIEW RESET 1 GND 2 5 VCC MAX823 MR 3 GND 2 4 SOT23/SC70 RESET 1 WDI 5 VCC MAX824 RESET 3 GND 2 4 WDI SOT23/SC70 RESET 1 5 VCC MAX825 RESET 3 4 MR SOT23/SC70 ________________________________________________________________ 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 MAX823/MAX824/MAX825 ________________General Description MAX823/MAX824/MAX825 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset ABSOLUTE MAXIMUM RATINGS VCC ........................................................................-0.3V to +6.0V All Other Pins..............................................-0.3V to (VCC + 0.3V) Input Current, All Pins Except RESET and RESET..............20mA Output Current, RESET, RESET ..........................................20mA Continuous Power Dissipation (TA = +70°C) 5-Pin SC70 (derate 3.1mW/°C above +70°C) ...............247mW 5-Pin SOT23 (derate 7.1mW/°C above +70°C).............571mW Operating Temperature Range MAX82_EXK......................................................-40°C to +85°C MAX82_EUK ...................................................-40°C to +125°C Storage Temperature Range .............................-65°C to +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 (VCC = +4.75V to +5.5V for MAX82_L, VCC = +4.5V to +5.5V for MAX82_M, VCC = +3.15V to +3.6V for MAX82_T, VCC = +3V to +3.6V for MAX82_S, VCC = +2.7V to +3.6V for MAX82_R, VCC = +2.38V to +2.75V for MAX82_Z, VCC = +2.25V to +2.75V for MAX82_Y, TA = TMIN to TMAX, TA = -40°C to +85°C (SC70), TA = -40°C to +125°C (SOT23), unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Operating Voltage Range Supply Current (SOT23 Only) SYMBOL VCC ISUPPLY CONDITIONS 1.0 TA = TMIN to TMAX 1.2 WDI and MR unconnected MR unconnected Supply Current (SC70 Only) ISUPPLY WDI and MR unconnected MR unconnected VRST 5 12 MAX825L/M 4.5 12 MAX825T/S/R/Z/Y 3 8 MAX823L/M MAX824L/M 6 17 MAX823T/S/R/Z/Y MAX824T/S/R/Z/Y 4 12 MAX825L/M 3 8 MAX825T/S/R/Z/Y 4.50 4.31 TA = TMIN to TMAX 4.25 TA = +25°C 3.04 TA = TMIN to TMAX 3.00 TA = +25°C 2.89 TA = TMIN to TMAX 2.85 TA = +25°C 2.59 TA = TMIN to TMAX 2.55 MAX82_Z (SC70 only) TA = +25°C 2.28 TA = TMIN to TMAX 2.25 MAX82_Y (SC70 only) TA = +25°C 2.16 TA = TMIN to TMAX 2.13 MAX82_R 2 MAX823T/S/R/Z/Y MAX824T/S/R/Z/Y TA = +25°C MAX82_S 5.5 24 TA = TMIN to TMAX MAX82_T MAX 10 4.56 MAX82_M TYP MAX823L/M MAX824L/M TA = +25°C MAX82_L Reset Threshold MIN TA = 0°C to +70°C 2 6 4.63 4.70 UNITS V µA µA 4.75 4.38 4.45 4.50 3.08 3.11 3.15 2.93 2.96 3.00 2.63 2.66 2.70 2.32 2.35 2.38 2.19 _______________________________________________________________________________________ 2.22 2.25 V 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset (VCC = +4.75V to +5.5V for MAX82_L, VCC = +4.5V to +5.5V for MAX82_M, VCC = +3.15V to +3.6V for MAX82_T, VCC = +3V to +3.6V for MAX82_S, VCC = +2.7V to +3.6V for MAX82_R, VCC = +2.38V to +2.75V for MAX82_Z, VCC = +2.25V to +2.75V for MAX82_Y, TA = TMIN to TMAX, TA = -40°C to +85°C (SC70), TA = -40°C to +125°C (SOT23), unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL Reset Threshold Hysteresis CONDITIONS MIN TYP MAX82_L/M 10 MAX82_T/S/R/Z/Y 5 Reset Threshold Temperature Coefficient Reset Timeout Period MAX mV ppm/°C 40 tRP VCC to RESET Delay 140 200 VRST - VCC = 100mV VOH RESET Output Voltage VOL 280 VCC - 1.5 MAX82_T/S/R/Z/Y, VCC = VRST max, ISOURCE = 30µA 0.8 ✕ VCC ms µs 20 MAX82_L/M, VCC = VRST max, ISOURCE = 120µA UNITS MAX82_L/M, VCC = VRST min, ISINK = 3.2mA 0.4 MAX82_T/S/R/Z/Y VCC = VRST min, ISINK = 1.2mA 0.3 TA = 0°C to +70°C, VCC = 1V, VCC falling, ISINK = 50µA 0.3 V TA = TMIN to TMAX, VCC = 1.2V, VCC falling, VBATT = 0V, ISINK = 100µA RESET Output Short-Circuit Current (Note 2) ISOURCE VOH RESET Output Voltage VOL MAX82_L/M, RESET = 0V, VCC = 5.5V 800 MAX82_T/S/R/Z/Y, RESET = 0V, VCC = 3.6V 400 VCC > 1.8V, ISOURCE = 150µA µA 0.8 ✕ VCC MAX824L/M, MAX825L/M, VCC = VRST max, ISINK = 3.2mA 0.4 MAX824T/S/R/Z/Y, MAX825T/S/R/Z/Y, VCC = VRST max, ISINK = 1.2mA 0.3 V WATCHDOG INPUT (MAX823/MAX824) Watchdog Timeout Period tWD WDI Pulse Width tWDI WDI Input Voltage (Note 3) WDI Input Current (Note 4) 1.12 VIL = 0.4V, VIH = 0.8 ✕ VCC 1.60 2.40 50 ns 0.3 ✕ VCC VIL 0.7 ✕ VCC VIH WDI = VCC, time average WDI = 0, time average 120 -20 s -15 160 V µA _______________________________________________________________________________________ 3 MAX823/MAX824/MAX825 ELECTRICAL CHARACTERISTICS (continued) MAX823/MAX824/MAX825 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset ELECTRICAL CHARACTERISTICS (continued) (VCC = +4.75V to +5.5V for MAX82_L, VCC = +4.5V to +5.5V for MAX82_M, VCC = +3.15V to +3.6V for MAX82_T, VCC = +3V to +3.6V for MAX82_S, VCC = +2.7V to +3.6V for MAX82_R, VCC = +2.38V to +2.75V for MAX82_Z, VCC = +2.25V to +2.75V for MAX82_Y, TA = TMIN to TMAX, TA = -40°C to +85°C (SC70), TA = -40°C to +125°C (SOT23), unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS MANUAL RESET INPUT (MAX823/MAX825) MR Input Voltage MR Pulse Width 0.3 ✕ VCC VIL VIH 0.7 ✕ VCC V µs 1.0 MR Noise Immunity (pulse width with no reset) 100 ns MR to Reset Delay 500 ns MR Pullup Resistance (internal) Note 1: Note 2: Note 3: Note 4: 4 35 52 75 kΩ Over-temperature limits are guaranteed by design and not production tested. The RESET short-circuit current is the maximum pullup current when RESET is driven low by a µP bidirectional reset pin. 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 to drive a three-stated output device with a 10µA maximum leakage current and a maximum capacitive load of 200pF. This output device must be able to source and sink at least 200µA when active. _______________________________________________________________________________________ 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset RESET TIMEOUT PERIOD vs. TEMPERATURE MAX823L 7 6 5 MAX824Y 4 3 MAX825R 2 220 210 200 190 180 170 VCC FALLING 25 20 15 10 5 160 150 -40 -20 0 20 40 60 80 0 -40 100 120 -20 0 20 40 60 80 100 -20 0 20 40 60 80 100 TEMPERATURE (°C) TEMPERATURE (°C) WATCHDOG TIMEOUT PERIOD vs. TEMPERATURE NORMALIZED RESET THRESHOLD VOLTAGE vs. TEMPERATURE MAXIMUM VCC TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.06 1.04 1.02 1.00 0.98 0.96 -20 0 20 40 60 TEMPERATURE (°C) 80 100 (SC70 ONLY) 45 40 35 30 25 RESET OCCURS ABOVE CURVE 20 MAX82_Y 15 10 MAX82_R 5 0.94 1.0 50 TRANSIENT DURATION (µs) 1.9 NORMALIZED RESET THRESHOLD (V) MAX823/4/5 toc04 2.0 -40 -40 TEMPERATURE (°C) MAX823/4/5 toc06 1 WATCHDOG TIMEOUT PERIOD (s) 230 30 MAX823/4/5 toc03 240 MAX823/4/5 toc05 SUPPLY CURRENT (µA) 8 250 MAX823/4/5 toc02 (SC70 ONLY) RESET TIMEOUT PERIOD (ms) MAX823/4/5 toc01 9 RESET COMPARATOR PROPAGATION DELAY vs. TEMPERATURE PROPAGATION DELAY (µs) VCC SUPPLY CURRENT vs. TEMPERATURE MAX82_L 0 -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 0 20 40 60 80 100 120 140 160 180 200 RESET THRESHOLD OVERDRIVE (mV), VRST - VCC _______________________________________________________________________________________ 5 MAX823/MAX824/MAX825 __________________________________________Typical Operating Characteristics MAX823_, VCC = +5V, TA = +25°C, unless otherwise noted.) 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset MAX823/MAX824/MAX825 Pin Description MAX823 PIN MAX824 MAX825 NAME FUNCTION Active-Low Reset Output. Pulses low for 200ms when triggered, and remains low whenever VCC is below the reset threshold or when MR is a logic low. It remains low for 200ms after one of the following occurs: VCC rises above the reset threshold, the watchdog triggers a reset, or MR goes low to high. 1 1 1 RESET 2 2 2 GND 3 — 4 MR — 3 3 RESET Ground Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as MR is held low and for 200ms after MR returns high. The active-low input has an internal 52kΩ pullup resistor. It can be driven from a CMOS logic line or shorted to ground with a switch. Leave open or connect to VCC if unused. Active-High Reset Output. Inverse of RESET. 4 4 — WDI Watchdog Input. If WDI remains either high or low for longer than the watchdog timeout period, the internal watchdog timer runs out and a reset is triggered. The internal watchdog timer clears whenever reset is asserted, or whenever WDI sees a rising or falling edge. If WDI is left unconnected or is connected to a three-stated buffer output, the watchdog feature is disabled. 5 5 5 VCC Supply Voltage VCC MAX823 MAX824 MAX825 RESET GENERATOR VCC RESET RESET (MAX824/MAX825 ONLY) 1.25V MR (MAX823/MAX825 ONLY) WDI (MAX823/MAX824 ONLY) WATCHDOG TRANSITION DETECTOR WATCHDOG TIMER GND Figure 1. Functional Diagram 6 _______________________________________________________________________________________ 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset Watchdog Input (MAX823/MAX824) A microprocessor’s (µP’s) reset input starts the µP in a known state. The MAX823/MAX824/MAX825 µP supervisory circuits assert a reset to prevent code-execution errors during power-up, power-down, and brownout conditions. RESET is guaranteed to be a logic low for VCC down to 1V. Once VCC exceeds the reset threshold, an internal timer keeps RESET low for the specified reset timeout period (tRP); after this interval, RESET returns high (Figure 2). If a brownout condition occurs (VCC dips below the reset threshold), RESET goes low. Each time RESET is asserted it stays low for the reset timeout period. Any time VCC goes below the reset threshold the internal timer restarts. RESET both sources and sinks current. RESET on the MAX824/MAX825 is the inverse of RESET. In the MAX823/MAX824, the watchdog circuit monitors the µP’s activity. If the µP does not toggle the watchdog input (WDI) within tWD (1.6s), reset asserts. The internal 1.6s timer is cleared by either a reset pulse or by toggling WDI, which detects pulses as short as 50ns. While reset is asserted, the timer remains cleared and does not count. As soon as reset is released, the timer starts counting (Figure 3). Disable the watchdog function by leaving WDI unconnected or by three-stating the driver connected to WDI. The watchdog input is internally driven low during the first 7/8 of the watchdog timeout period and high for the last 1/8 of the watchdog timeout period. When WDI is left unconnected, this internal driver clears the 1.6s timer every 1.4s. When WDI is three-stated or unconnected, the maximum allowable leakage current is 10µA and the maximum allowable load capacitance is 200pF. Manual Reset Input (MAX823/MAX825) Applications Information Many µP-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. On the MAX823/ MAX825, a logic low on MR asserts reset. Reset remains asserted while MR is low, and for tRP (200ms nominal) after it returns high. MR has an internal 52kΩ pullup resistor, so it can be left open if not used. This input can be driven with 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. If MR is driven from long cables or the device is used in a noisy environment, connect a 0.1µF capacitor from MR to GND to provide additional noise immunity. The MAX823/MAX824 WDI inputs are internally driven through a buffer and series resistor from the watchdog counter (Figure 1). 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. For minimum watchdog input current (minimum overall power consumption), leave WDI low for the majority of the watchdog timeout period, pulsing it low-high-low once within the first 7/8 of the watchdog timeout period to reset the watchdog timer. If WDI is externally driven high for the majority of the timeout period, up to 160µA can flow into WDI. RESET Output VCC VCC 1V Watchdog Input Current VRST VRST tRST 1V RESET* RESET tRP tRD RESET tRP tRD tRP tWD tRP WDI GND *RESET ON THE MAX824/MAX825 IS THE INVERSE OF RESET. Figure 2. Reset Timing Diagram Figure 3. MAX823/MAX824 Watchdog Timing Relationship _______________________________________________________________________________________ 7 MAX823/MAX824/MAX825 _______________Detailed Description MAX823/MAX824/MAX825 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset Interfacing to µPs with Bidirectional Reset Pins The RESET output maximum pullup current is 800µA for L/M versions (400µA for T/S/R/Z/Y versions). This allows µPs with bidirectional resets, such as the 68HC11, to force RESET low when the MAX823/MAX824/MAX825 are pulling RESET high (Figure 4). Negative-Going VCC Transients These supervisors are relatively immune to shortduration, negative-going VCC transients (glitches), which usually do not require the entire system to shut down. Resets are issued to the µP during power-up, powerdown, and brownout conditions. The Typical Operating Characteristics show a graph of the MAX823_’s Maximum VCC Transient Duration vs. Reset Threshold Overdrive, for which reset pulses are not generated. The graph was produced using negative-going VCC pulses, starting at 5V and ending below the reset threshold by the magnitude indicated (reset threshold overdrive). The graph shows the maximum pulse width that a negative-going VCC transient can typically have without triggering a reset pulse. As the amplitude of the transient increases (i.e., goes farther below the reset threshold), the maximum allowable pulse width decreases. An optional 0.1µF bypass capacitor mounted close to VCC provides additional transient immunity. Watchdog Software Considerations (MAX823/MAX824) 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. Figure 5 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 beginning 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 quickly be 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 input current than does leaving WDI low for the majority of the timeout period and periodically pulsing it low-high-low. VCC START VCC SET WDI HIGH VCC MAX823 MAX824 MAX825 ISOURCE MAX = 800µA L, M 400µA T, S, R, Z, Y RESET GENERATOR VCC PROGRAM CODE RESET µP SUBROUTINE OR PROGRAM LOOP SET WDI LOW GND GND RETURN Figure 4. Interfacing to µPs with Bidirectional Resets 8 Figure 5. Watchdog Flow Diagram _______________________________________________________________________________________ 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset ____________________Chip Information TRANSISTOR COUNT: 607 VCC VCC PROCESS TECHNOLOGY: BiCMOS VCC RESET RESET MAX823 µP WDI I/O MR MANUAL RESET GND GND Ordering Information (continued) PART† TEMP. RANGE MAX824_EUK-T -40°C to +125°C PIN-PACKAGE 5 SOT23-5 MAX825_EXK-T -40°C to +85°C 5 SC70-5 MAX825_EUK-T -40°C to +125°C 5 SOT23-5 †Insert the desired suffix letter (from the Reset Threshold table) into the blank to complete the part number. All devices are available in tape-and-reel only. There is a 2,500 piece minimum order increment. Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing “-T” with “+T” when ordering. Marking Information MARKING INFORMATION (TOP) XXXX (SC70 ONLY) MARKING INFORMATION (TOP) XXXX (SOT ONLY) AAAI = MAX823L AAAJ = MAX823M AAAK = MAX823T AAAL = MAX823S AAAM = MAX823R AAAN = MAX824L AAAO = MAX824M AAAP = MAX824T AAAQ = MAX824S AAAR = MAX824R AAAS = MAX825L AAAT = MAX825M AAAU = MAX825T AAAV = MAX825S AAAW = MAX825R AAL = MAX823L AAM = MAX823M AAP = MAX823R AAO = MAX823S AAN = MAX823T AAR = MAX823Y AAQ = MAX823Z AAS = MAX824L AAT = MAX824M AAW = MAX824R AAV = MAX824S AAU = MAX824T AAY = MAX824Y AAX = MAX824Z AAZ = MAX825L ABA = MAX825M ABD = MAX825R ABC = MAX825S ABB = MAX825T ABF = MAX825Y ABE = MAX825Z _______________________________________________________________________________________ 9 MAX823/MAX824/MAX825 Typical Operating Circuit 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.) SOT-23 5L .EPS MAX823/MAX824/MAX825 5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset PACKAGE OUTLINE, SOT-23, 5L 21-0057 E 1 1 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. 10 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.