19-5212; Rev 4/10 DS1705/DS1706 3.3V and 5.0V MicroMonitor www.maxim-ic.com FEATURES PIN ASSIGNMENT  Halts and restarts an out-of-control microprocessor PBRST 1 8 WDS  Holds microprocessor in check during power V 2 7 RST CC transients GND 3 6 ST  Automatically restarts microprocessor after IN 4 5 NMI power failure 8-Pin DIP (300 -mil)  Monitors pushbutton for external override  Accurate 5%, 10% or 20% resets for 3.3V PBRST 1 8 WDS systems and 5% or 10% resets for 5.0V V 2 7 RST(*RST) systems CC  Eliminates the need for discrete components GND 3 6 ST  3.3V 20% tolerance for use with 3.0V IN 4 5 NMI systems 8-Pin SOIC (150-mil)  Pin-compatible with the MAXIM RST(*RST) 1 8 ST MAX705/MAX706 in 8-pin DIP, 8-pin SOIC, WDS 2 7 NMI and -SOP PBRST 3 6 IN  8-pin DIP, 8-pin SOIC and 8-pin -SOP VCC 4 5 GND packages 8-Pin -SOP (118-mil) See Mech. Drawings Section on website  Industrial temperature range -40C to +85C DS1705 and DS1706_R/S/T (*DS1706L and DS1706P) PIN DESCRIPTION PBRST - Pushbutton Reset Input V - Power Supply CC GND - Ground IN - Input NMI - Non-maskable Interrupt ST - Strobe Input RST - Active Low Reset Output *RST - Active High Reset Output (DS1706P and DS1706L only) WDS - Watchdog Status Output DESCRIPTION The DS1705/DS1706 3.3- or 5.0-Volt MicroMonitor monitors three vital conditions for a microprocessor: power supply, software execution, and external override. A precision temperature compensated reference and comparator circuit monitor the status of V at the device and at an upstream point for maximum CC protection. When the sense input detects an out-of-tolerance condition, a non-maskable interrupt is generated. As the voltage at the device degrades, an internal power fail signal is generated which forces 1 of 12

DS1705/DS1706 the reset to an active state. When V returns to an in-tolerance condition, the reset signal is kept in the CC active state for a minimum of 130 ms to allow the power supply and processor to stabilize. The second function the DS1705/DS1706 performs is pushbutton reset control. The DS1705/DS1706 debounces the pushbutton input and guarantees an active reset pulse width of 130 ms minimum. The third function is a watchdog timer. The DS1705/DS1706 has an internal timer that forces the WDS output signal to the active state if the strobe input is not driven low prior to time-out. OPERATION Power Monitor The DS1705/DS1706 detects out-of-tolerance power supply conditions and warns a processor-based system of impending power failure. When V falls below the minimum V tolerance, a comparator CC CC outputs the RST (or RST) signal. RST (or RST) is an excellent control signal for a microprocessor, as processing is stopped at the last possible moment of valid V . On power-up, RST (or RST) are kept CC active for a minimum of 130 ms to allow the power supply and processor to stabilize. Pushbutton Reset The DS1705/DS1706 provides an input pin for direct connection to a pushbutton reset (see Figure 2). The pushbutton reset input requires an active low signal. Internally, this input is debounced and timed such that a RST (or RST) signal of at least 130 ms minimum will be generated. The 130 ms delay commences as the pushbutton reset input is released from the low level. The pushbutton can be initiated by connecting the WDS or NMI outputs to the PBRST input as shown in Figure 3. Non-Maskable Interrupt The DS1705/DS1706 generates a non-maskable interrupt (NMI) for early warning of a power failure. A precision comparator monitors the voltage level at the IN pin relative to an on-chip reference generated by an internal band gap. The IN pin is a high impedance input allowing for a user-defined sense point. An external resistor voltage divider network (Figure 5) is used to interface with high voltage signals. This sense point may be derived from a regulated supply or from a higher DC voltage level closer to the main system power input. Since the IN trip point V is 1.25 volts, the proper values for R1 and R2 can be TP determined by the equation as shown in Figure 5. Proper operation of the DS1705/DS1706 requires that the voltage at the IN pin be limited to V . Therefore, the maximum allowable voltage at the supply being CC monitored (V ) can also be derived as shown in Figure 5. A simple approach to solving the equation is MAX to select a value for R2 high enough to keep power consumption low, and solve for R1. The flexibility of the IN input pin allows for detection of power loss at the earliest point in a power supply system, maximizing the amount of time for system shutdown between NMI and RST (or RST). When the supply being monitored decays to the voltage sense point, the DS1705/DS1706 pulses the NMI output to the active state for a minimum 200 s. The NMI power-fail detection circuitry also has built-in hysteresis of 100 V. The supply must be below the voltage sense point for approximately 5 s before a low NMI will be generated. In this way, power supply noise is removed from the monitoring function, preventing false interrupts. During a power-up, any detected IN pin levels below V by the comparator TP are disabled from generating an interrupt until V rises to V . As a result, any potential NMI pulse CC CCTP will not be initiated until V reaches V . CC CCTP Connecting NMI to PBRST would allow non-maskable interrupt to generate an automatic reset when an out-of-tolerance condition occurred in a monitored supply. An example is shown in Figure 3. 2 of 12

DS1705/DS1706 Watchdog Timer The watchdog timer function forces WDS signals active when the ST input is not clocked within the 1 second time-out period. Time-out of the watchdog starts when RST (or RST) becomes inactive. If a high- to-low transition occurs on the ST input pin prior to time-out, the watchdog timer is reset and begins to time out again. If the watchdog timer is allowed to time out, the WDS signal is driven active (low) for a minimum of 130 ms. The ST input can be derived from many microprocessor outputs. The typical signals used are the microprocessors address signals, data signals, or control signals. When the microprocessor functions normally, these signals would, as a matter of routine, cause the watchdog to be reset prior to time-out. To guarantee that the watchdog timer does not time out, a high-to-low transition must occur at or less than the minimum watchdog time-out of 1 second. A typical circuit example is shown in Figure 6. MICROMONITOR BLOCK DIAGRAM Figure 1 40k 180k PUSH-BUTTON RESET Figure 2 3 of 12

DS1705/DS1706 PUSH-BUTTON RESET CONTROLLED BY NMI AND WDS Figure 3 TIMING DIAGRAM: PUSHBUTTON RESET Figure 4 NON-MASKABLE INTERRUPT CIRCUIT EXAMPLE Figure 5 R1 R2 V SENSE V = X 1.25 V = X V SENSE MAX CC R2 V TP Example: V = 4.50V at the trip point SENSE V = 3.3V CC 10 kΩ = R2 4.50 Therefore: X 3.3 = 11.88V maximum 1.25 R1  10k 4.5 = X 1.25 R1 = 26 kΩ 10k 4 of 12

DS1705/DS1706 WATCHDOG TIMER Figure 6 TIMING DIAGRAM: STROBE INPUT Figure 7 TIMING DIAGRAM: NON-MASKABLE INTERRUPT Figure 8 5 of 12

DS1705/DS1706 TIMING DIAGRAM: POWER-DOWN Figure 9 6 of 12

DS1705/DS1706 TIMING DIAGRAM: POWER-UP Figure 10 7 of 12

DS1705/DS1706 ABSOLUTE MAXIMUM RATINGS Voltage Range on V Pin Relative to Ground -0.5V to +7.0V CC Voltage Range on I/O Relative to Ground* -0.5V to (V + 0.5V) CC Operating Temperature Range -40C to +85C Storage Temperature Range -55C to +125C Lead Temperature (soldering, 10s) +260C Soldering Temperature (reflow) Lead(Pb)-free +260C Containing lead(Pb) +240C This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. *The voltage input on IN, ST, and PBRST can be exceeded if the input current is less than 10 mA. RECOMMENDED DC OPERATING CONDITIONS (T = -40C to +85C) A PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Supply Voltage V 1.2 5.5 V 1 CC ST and PBRST Input High Level VIH 2.0 VCC+0.3 V 1, 3 V -0.5 1, 4 CC ST and PBRST Input Low Level VIL -0.03 +0.5 V 1 DC ELECTRICAL CHARACTERISTICS (V = 1.2V to 5.5V, T = -40C to +85C.) CC A PARAMETER SYMBOL MIN TYP MAX UNITS NOTES V Trip Point DS1705/DS1706L V 4.50 4.65 4.75 V 1 CC CCTP V Trip Point DS1706 V 4.25 4.40 4.50 V 1 CC CCTP V Trip Point DS1706T V 3.00 3.08 3.15 V 1 CC CCTP V Trip Point DS1706S V 2.85 2.93 3.00 V 1 CC CCTP V Trip Point DS1706P or R V 2.55 2.63 2.70 V 1 CC CCTP Input Leakage I -1.0 +1.0 A 2 IL Output Current @ 2.4V I 350 A 3 OH Output Current @ 0.4V I 10 mA 3 OL Output Voltage @ -500 A V V -0.3 V -0.1 V 3 OH CC CC Operating Current I 60 A 5 CC @ V < 5.5V CC Operating Current I 50 A 5 CC @ V < 3.6V CC IN Input Trip Point V 1.20 1.25 1.30 V 1 TP CAPACITANCE (T = +25C) A PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Input Capacitance C 5 pF IN Output Capacitance C 7 pF OUT 8 of 12

DS1705/DS1706 AC ELECTRICAL CHARACTERISTICS (V = 1.2V to 5.5V, T = -40C to +85C.) CC A PARAMETER SYMBOL MIN TYP MAX UNITS NOTES PBRST = VIL tPB 150 ns Reset Active Time t 130 205 285 ms RST ST Pulse Width tST 10 ns 6 VCC Detect to RST and RST tRPD 5 8 s 9 V Slew Rate t 20 s CC F VCC Detect to RST and RST tRPU 130 205 285 ms 7 V Slew Rate t 0 ns CC R PBRST Stable Low to RST and RST tPDLY 250 ns Watchdog Timeout t 1.0 1.6 2.2 s 8 TD VIN Detect to NMI tIPD 5 8 s 9 NOTES: 1. All voltages are referenced to ground. 2. PBRST is internally pulled up to V with an internal impedance of 40 ktypical and the ST input is CC internally pulled up to V with an internal impedance of 180 ktypical. CC 3. V ≥ 2.4V. CC 4. V < 2.4V. CC 5. Measured with outputs open and all inputs at V or ground. CC 6. Must not exceed t minimum. TD 7. t = 5 s. R 8. Minimum watchdog time-out tested at 2.7V for the 3.3V devices and 4.5V for the 5.0V devices. 9. Noise immunity  pulses < 2 s will not cause a reset. 9 of 12

DS1705/DS1706 PART MARKING CODES DS170AB 8-pin DIP yywwrv cccccc (300 MIL) ###xx 8-pin SOIC DS170AB yywwrv (150 MIL) ###xx cccccc 8-pin µSOP 170AB (118 MIL) ywwrv ###xx BRAND CODES CODE DESCRIPTION VALUES AB Device type and tolerance 5_, 6_, 6L, 6P, 6R, 6S, 6T (where’_’ is a blank) yww or yyww Date Code. Identifies the year and work y, the last digit of the year. week the device was assembled. yy, the last two digits of the year. ww, the work week (values 01 through 52). rv Die Revision A letter followed by a number (eg. B1) ###xx Lot Code Three numbers followed by 2 letters cccccc Country of Assembly Abbreviation of country name. 10 of 12

DS1705/DS1706 ORDERING INFORMATION PART TEMP RANGE PIN-PACKAGE VERSION DS1705EPA -40°C to +85°C 8-pin PDIP (300 mils) 5V-5% MONITOR, /RST, /WDS DS1705ESA -40°C to +85°C 8-pin SO (150 mils) 5V-5% MONITOR, /RST, /WDS DS1705EUA -40°C to +85°C 8-pin µSOP (118 mils) 5V-5% MONITOR, /RST, /WDS DS1706EPA -40°C to +85°C 8-pin PDIP (300 mils) 5V-10% MONITOR, /RST, /WDS DS1706ESA -40°C to +85°C 8-pin SO (150 mils) 5V-10% MONITOR, /RST, /WDS DS1706EUA -40°C to +85°C 8-pin µSOP (118 mils) 5V-10% MONITOR, /RST, /WDS DS1706LEPA -40°C to +85°C 8-pin PDIP (300 mils) 5V-5% MONITOR, RST, /WDS DS1706LESA -40°C to +85°C 8-pin SO (150 mils) 5V-5% MONITOR, RST, /WDS DS1706LEUA -40°C to +85°C 8-pin µSOP (118 mils) 5V-5% MONITOR, RST, /WDS DS1706PEPA -40°C to +85°C 8-pin PDIP (300 mils) 3.3V-20% MONITOR, RST, /WDS DS1706PESA -40°C to +85°C 8-pin SO (150 mils) 3.3V-20% MONITOR, RST, /WDS DS1706PEUA -40°C to +85°C 8-pin µSOP (118 mils) 3.3V-20% MONITOR, RST, /WDS DS1706REPA -40°C to +85°C 8-pin PDIP (300 mils) 3.3V-20% MONITOR, /RST, /WDS DS1706RESA -40°C to +85°C 8-pin SO (150 mils) 3.3V-20% MONITOR, /RST, /WDS DS1706REUA -40°C to +85°C 8-pin µSOP (118 mils) 3.3V-20% MONITOR, /RST, /WDS DS1706SEPA -40°C to +85°C 8-pin PDIP (300 mils) 3.3V-10% MONITOR, /RST, /WDS DS1706SESA -40°C to +85°C 8-pin SO (150 mils) 3.3V-10% MONITOR, /RST, /WDS DS1706SEUA -40°C to +85°C 8-pin µSOP (118 mils) 3.3V-10% MONITOR, /RST, /WDS DS1706TEPA -40°C to +85°C 8-pin PDIP (300 mils) 3.3V-5% MONITOR, /RST, /WDS DS1706TESA -40°C to +85°C 8-pin SO (150 mils) 3.3V-5% MONITOR, /RST, /WDS DS1706TEUA -40°C to +85°C 8-pin µSOP (118 mils) 3.3V-5% MONITOR, /RST, /WDS Note: Devices are also available in a lead(Pb)-free/RoHS-compliant package. Specify lead-free by adding a plus (+) to the part number when ordering. E = -40°C to +85°C temperature range A = 8-lead device P = Plastic DIP (300 mils) S = SO (150 mils) U = µSOP (118 mils) PACKAGE INFORMATION For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 8 PDIP P8-2 21-0043 8 SO S8-2 21-0041 8 SOP U8-1 21-0036 11 of 12

DS1705/DS1706 REVISION HISTORY REVISION PAGES DESCRIPTION DATE CHANGED Added the lead temperature and updated the soldering 4/10 8, 9 temperature in the Absolute Maximum Ratings; corrected Note 9. 12 of 12 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 © 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Maxim Integrated Products, Inc.

Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: M axim Integrated: DS1706EUA+ DS1705EPA+ DS1705ESA+ DS1705ESA+T&R DS1706ESA+ DS1706LEPA+ DS1706LESA+ DS1706LESA+T&R DS1706RESA+ DS1706SESA+ DS1706TESA+ DS1705EPA DS1705ESA DS1705EUA+ DS1705EUA+T&R DS1706EPA DS1706EPA+ DS1706ESA+T&R DS1706EUA+T&R DS1706LEPA DS1706LEUA+ DS1706LEUA+T&R DS1706PEPA DS1706PEPA+ DS1706PESA+ DS1706PESA+T&R DS1706PEUA+ DS1706PEUA+T&R DS1706REPA+ DS1706RESA+T&R DS1706REUA+ DS1706REUA+T&R DS1706SEPA+ DS1706SESA+T&R DS1706SEUA+ DS1706SEUA+T&R DS1706TEPA+ DS1706TESA DS1706TESA+T&R DS1706TEUA+ DS1706TEUA+T&R