DS1708SEPA

DS1707ESA MAXIM | Alldatasheet

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Technical content

FEATURES

/g167/g32Holds microprocessor in check during power transients /g167/g32Automatically restarts microprocessor after power failure /g167/g32Monitors pushbutton for external override /g167/g32Accurate 5%, 10% or 20% resets for 3.3V systems and 5% or 10% resets for 5.0V systems /g167/g32Eliminates the need for discrete components /g167/g3220% tolerance compatible with 3.0V systems /g167/g32Pin compatible with the MAXIM MAX707/MAX708 in 8-pin DIP, 8-pin SOIC packages /g167/g328-pin DIP, 8-pin and /g109-SOP SOIC and 8-pin /g109-SOP packages available /g167/g32Industrial temperature range -40/g176C to +85/g176C PIN ASSIGNMENT See Mech. Drawings Section on website DS1707 and DS1708_R/S/T PIN DESCRIPTION PBRST - Pushbutton Reset Input VCC - Power Supply GND - Ground IN - Input NMI - Non-maskable Interrupt NC - No Connect RST - Active Low Reset Output RST - Active High Reset Output

DESCRIPTION

The DS1707/DS1708 3.3- or 5.0-Volt MicroMonitor monitors three vital conditions for a microprocessor: power supply, voltage sense, and external override . A precision temperature-compensated reference and comparator circuit monitor the status of V CC at the device and at an upstream point for maximum 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 the reset to an active state. When V CC returns to an in-tolerance conditi on, the reset signal is kept in the active state for a minimum of 130 ms to allow the power supply and processor to stabilize. DS1707/DS1708 3.3 and 5.0-Volt MicroMonitor www.maxim-ic.com 8-Pin DIP (300-mil) PBRST VCC GND IN RST RST NC NMI 8-Pin /g109-SOP (118-mil) RST RST PBRST VCC NC NMI IN GND 8-Pin SOIC (150-mil) PBRST VCC GND IN RST RST NC NMI

The third function the DS1707/DS1708 performs is pushbutton reset control. The DS1707/DS1708 debounces the pushbutton input and guarantees an active reset pulse width of 130 ms minimum. OPERATION Power Monitor The DS1707/DS1708 detects out-of-tole rance power supply conditions and warns a processor-based system of impending power failure. When V CC falls below the minimum V CC tolerance, a comparator outputs the RST and RST signals. RST and RST are excellent control signals for a microprocessor, as processing is stopped at the la st possible moment of valid V CC. On power-up, RST and RST are kept active for a minimum of 130 ms to allow the power supply and processor to stabilize. Pushbutton Reset The DS1707/DS1708 provides an input pin for direct connection to a pushbutton reset (see Figure 2). The pushbutton reset input requires an ac tive low signal. Internally, this input is debounced and timed such that RST and RST signals 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 NMI output to the PBRST input as shown in Figure 3. Non-Maskable Interrupt The DS1707/DS1708 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 TP is 1.25 volts, the proper values for R1 and R2 can be determined by the equation as shown in Figure 5. Proper operation of th e DS1707/DS1708 requires that the voltage at the IN pin be limited to VCC. Therefore, the maximum allowable voltage at the supply being monitored (VMAX) can also be derived as shown in Figure 5. A simple approach to solving the equation is 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 lo ss at the earliest point in a power supply system, maximizing the amount of time for system shut-down between NMI and RST/ RST . When the supply being monitored decays to the voltage sense point, the DS1707/DS1708 pulses the NMI output to the active state for a minimum 200 /g109s. The NMI power-fail detection circuitry also has built-in hysteresis of 100 /g109V. The supply must be below the volta ge sense point for approximately 5 /g109s before a low NMI will be generated. In this way, power supply noise is removed from the monitoring function, preventing false interrupts. During a powe r-up, any detected IN pin levels below V TP by the comparator are disabled from generating an interrupt until V CC rises to V CCTP. As a result, any potential NMI pulse will not be initiated until VCC reaches VCCTP. Connecting NMI to PBRST would allow the 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.

MICROMONITOR BLOCK DIAGRAM Figure 1 40k/g87 PUSHBUTTON RESET Figure 2 PUSHBUTTON RESET CONTROLLED BY NMI Figure 3

TIMING DIAGRAM: PUSHBUTTON RESET Figure 4 NON-MASKABLE INTERRUPT CIRCUIT EXAMPLE Figure 5 V SENSE = R2 R2 R1/g43 X 1.25 V MAX = TP SENSE V V X VCC Example: V SENSE = 4.50V at the trip point V CC = 3.3V 1 0 k Ω = R2 Therefore: 25.1 50.4 X 3.3 = 11.88V maximum 4.50 = 10k 10k R1/g43 X 1.25 R1 = 26 k Ω

TIMING DIAGRAM: NON-MASKABLE INTERRUPT Figure 6 TIMING DIAGRAM: POWER-DOWN Figure 7

TIMING DIAGRAM: POWER UP Figure 8

ABSOLUTE MAXIMUM RATINGS* Voltage on VCC Pin Relative to Ground -0.5V to +7.0V Voltage on I/O Relative to Ground** -0.5V to V CC + 0.5V Operating Temperature -40 /g176C to +85/g176C Storage Temperature -55 /g176C to +125/g176C Soldering Temperature 260 /g176C for 10 seconds * 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 limits on IN and PBRST can be exceeded if the input current is less than 10 mA. RECOMMENDED DC OPERATING CONDITIONS (-40/g176C to +85/g176C) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Supply Voltage V CC 1.2 5.5 V 1 PBRST Input High Level VIH 2.0 VCC-0.5 V CC+0.3 V 1, 3 1, 4 PBRST Input Low Level VIL -0.03 +0.5 V 1 DC ELECTRICAL CHARACTERISTICS (-40/g176C to +85/g176C; VCC=1.2V to 5.5V) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES VCC Trip Point DS1707 V CCTP 4.50 4.65 4.75 V 1 VCC Trip Point DS1708 V CCTP 4.25 4.40 4.50 V 1 VCC Trip Point DS1708T V CCTP 3.00 3.08 3.15 V 1 VCC Trip Point DS1708S V CCTP 2.85 2.93 3.00 V 1 VCC Trip Point DS1708R V CCTP 2.55 2.63 2.70 V 1 Input Leakage I IL -1.0 +1.0 /g109A 2 Output Current @ 2.4V I OH 350 /g109A 3 Output Current @ 0.4V I OL 10 mA 3 Output Voltage @ -500µA V OH V CC-0.3 V CC-0.1 V 3 Operating Current @ VCC < 5.5V I CC 60 /g109A 5 Operating Current @ VCC < 3.6V I CC 50 /g109A 5 IN Input Trip Point V TP 1.20 1.25 1.30 V 1 CAPACITANCE (tA=25/g176C) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Input Capacitance C IN 5 pF Output Capacitance C OUT 7 pF

AC ELECTRICAL CHARACTERISTICS (-40/g176C to +85/g176C; VCC=1.2V to 5.5V) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES PBRST = VIL tPB 150 ns Reset Active Time t RST 130 205 285 ms VCC Detect to RST and RST tRPD 5 8 /g109s 7 VCC Slew Rate t F 20 /g109s VCC Detect to RST and RST tRPU 130 205 285 ms 6 VCC Slew Rate t R 0 ns PBRST Stable Low to RST and RST tPDLY 250 ns VIN Detect to NMI tIPD 5 8 /g109s 7 NOTES: 1. All voltages are referenced to ground. 2. PBRST is internally pulled up to VCC with an internal impedance of 40 k/g87 typical. 3. V CC ≥ 2.4V 4. V CC < 2.4V 5. Measured with outputs open and all inputs at V CC or ground. 6. t R = 5 /g109s 7. Noise immunity - pulses < 2 /g109s at VCCTP minimum will not cause a reset.

###xx 8-pin DIP (300 MIL) 8-pin SOIC (150 MIL) 8-pin µSOP (118 MIL) DS170AB yywwrv ###xx DS170AB yywwrv ###xx 170ABywwrv Brand Codes Code Description Values AB Device type and tolerance 7_, 8_, 8R, 8S, 8T (where’_’ is a blank) yww or yyww Date Code. Identifies the year and work week the device was assembled. y, the last digit of the year. 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.

ORDERING INFORMATION

DS1707EPA 8-pin DIP (300mil) -40°C TO +85°C 5V-5% MONITOR, /RST, RST DS1707ESA 8-pin SOIC (150 mil) -40°C TO +85°C 5V-5% MONITOR, /RST, RST DS1707EUA 8-pin µSOP (118 mil) -40°C TO +85°C 5V-5% MONITOR, /RST, RST DS1708EPA 8-pin DIP (300mil) -40°C TO +85°C 5V-10% MONITOR, /RST, RST DS1708ESA 8-pin SOIC (150 mil) -40°C TO +85°C 5V-10% MONITOR, /RST, RST DS1708EUA 8-pin µSOP (118 mil) -40°C TO +85°C 5V-10% MONITOR, /RST, RST DS1708REPA 8-pin DIP (300mil) -40°C TO +85°C 3.3V-20% MONITOR, /RST, RST DS1708RESA 8-pin SOIC (150 mil) -40°C TO +85°C 3.3V-20% MONITOR, /RST, RST DS1708REUA 8-pin µSOP (118 mil) -40°C TO +85°C 3.3V-20% MONITOR, /RST, RST DS1708SEPA 8-pin DIP (300mil) -40°C TO +85°C 3.3V-10% MONITOR, /RST, RST DS1708SESA 8-pin SOIC (150 mil) -40°C TO +85°C 3.3V-10% MONITOR, /RST, RST DS1708SEUA 8-pin µSOP (118 mil) -40°C TO +85°C 3.3V-10% MONITOR, /RST, RST DS1708TEPA 8-pin DIP (300mil) -40°C TO +85°C 3.3V-5% MONITOR, /RST, RST DS1708TESA 8-pin SOIC (150 mil) -40°C TO +85°C 3.3V-5% MONITOR, /RST, RST DS1708TEUA 8-pin µSOP (118 mil) -40°C TO +85°C 3.3V-5% MONITOR, /RST, RST *Contact factory for availability of Pb-free versions. E = -40°C to +85°C temperature range A = 8 lead device P = Plastic DIP (300 mil) S = SOIC (150 mil) U = µSOP (118 mil)