MIC2755 Micrel, Inc. MIC1232 µP Supervisory Circuit General Description Features The MIC1232 is a multifunction circuit which monitors microprocessor activity, external reset and power supplies in microprocessor based systems. The circuit functions include a watchdog time, power supply monitor, microprocessor reset, and manual pushbutton reset input. The power supply line is monitored with a comparator and an internal voltage reference. /RST is forced low when an out-of-tolerance condition exists and remains asserted for at least 250ms after VCC rises above the threshold voltage (4.5V or 4.75V). The /RST pin will remain logic low with VCC as low as 1.4V. The Watchdog input (/ST) monitors µP activity and will assert /RST if no µP activity has occurred with in the watchdog timeout period. The watchdog timeout period is selectable with nominal period of 150, 600, 1200 milliseconds. • Power OK/Reset time delay, 250ms min. • Watchdog timer, 150ms, 600ms, or 1.2s typical • Precision supply voltage monitor, select between 5% or 10% of supply voltage • Available in 8-pin surface mount (SO) • Debounced External reset input • Low supply current, <18µA typical Applications • • • • • Automotive systems Intelligent systems Critical microprocessor power monitoring Battery powered computers Controllers Ordering Information Part Number Temperature Range Package MIC1232NY –40ºC to +85ºC 8-Pin PDIP MIC1232MY –40ºC to +85ºC 8-Pin SOIC Standard Pb-Free MIC1232N MIC1232M Typical Application VCC TD VCC MIC1232 µP VCC PBRST ST RST I/O RESET TOL GND Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com January 2006 1 MIC1232 MIC1232 Micrel, Inc. Pin Configuration PBRST 1 8 TD 2 7 ST TOL 3 6 RST GND 4 5 RST MIC1232 VCC 8-Pin PDIP Package 8-Pin SOIC Package Pin Description Pin Number Pin Name 1 /PBRST Pushbutton Reset Input: This input is debounced and can be driven with external logic signals or by means of a mechanical pushbutton to actively force a reset. All pulses less than 1ms in duration on the /PBRST pin are ignored, whereas, any pulse with a duration of 20ms or greater is guaranteed to cause a reset. 2 TD 3 TOL Time Delay input: This input selects the timebase used by the watchdog timer. When TD = 0V, the watchdog timeout period is set to a normal value of 150ms, when TD = open, the watchdog timeout period is et to a nominal value of 600ms and when TD = VCC, the watchdog period is 1.2s nominally. 4 GND 5 RST RST is asserted high if either VCC goes below the reset threshold, the watchdog times out or /PBRST is pulled low for a minimum of 20ms. RST remains asserted for one reset timeout period after VCC exceeds the reset threshold or after the watch times out or after /PBRST goes high. 6 /RST /RST is asserted low if either VCC goes below the reset threshold, the watchdog times out or /PBRST is pulled low for a minimum of 20ms. /RST remains asserted for one reset timeout period after VCC exceeds the reset threshold or after the watch times out or after /PBRST goes high. Open-drain output 7 /ST Input to watchdog timer. If /ST does not see a transition from high to low within the watchdog timeout period, RST and /RST will be asserted. 8 VCC Primary supply input, +5V MIC1232 Pin Function Tolerance Select Input: Selects whether 5% or 10% of VCC is used as the reset threshold voltage. When TOL = 0V, the 5% tolerance level is selected and when TOL = VCC, a 10% tolerance level is selected. IC ground pin, 0V reference 2 January 2006 MIC2755 Micrel, Inc. Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Terminal Voltage VCC ..........................................................–0.3V to +6.0V All other inputs ...............................–0.3V to (VCC + 0.3V) Input Current VCC ...................................................................... 250mA GND, all other inputs .............................................. 25mA Lead Temperature (soldering, 10 sec.) ...................... 300°C Storage Temperature .................................. –65°C to 150°C ESD Rating, Note 3 Operating Temperature Range MIC1232M/N ............................................ –40°C to 85°C Electrical Characteristics VCC = 4.5V to 5.5V; TA = Operating Temperature Range, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted Parameter Condition Min Supply Voltage Range VCC 4.5 VIH, (Note 5) 2.0 Supply Current /ST and /PBRST Input Levels Input Leakage ICC, (Note 4) Typ 18 –0.3 VIL IIL Units 5.5 V 40 µA VCC+0.3 V 0.8 V ±1 µA 1.0 10 mA VOL = 0.4V 2.0 10 mA TOL = GND 4.5 4.62 4.74 V VCC 10% Trip Point (Reset Threshold Voltage) TOL = VCC 4.25 4.37 4.49 V Input Capacitance, /ST, TOL CIN, (Note 6) 5 pF 7 pF Output Souce Current, RST Output Sink Current, /RST. RST VCC 5% Trip Point (Reset Threshold Voltage) Output Capacitance, /RST, RST VOH = 2.4V Max COUT, (Note 6) AC Electrical Characteristics VCC = 4.5V to 5.5V; TA = Operating Temperature Range, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted /PBRST Min. Pulse Width, tPB /PBRST Delay, tPBD /PBRST = VIL (Note 7) 20 Reset Active Time, tRST /ST Pulse Width, tST /ST Timeout Period, tTD VCC Fall Time, tF VCC Rise Time, tR VCC Detect to /RST Low and RST High, tRPD VCC Detect to /RST Low and RST Low, tRPD 4 20 250 610 1000 62.5 150 250 ms TD = Open 250 600 1000 ms TD = VCC 500 1200 2000 ms 10 µs 0 VCC Falling (Note 8) VCC Falling (Note 9) 250 Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. Note 4. ICC is measured with outputs open and inputs within 0.5V of supply rails ns 50 150 µs 610 1000 µs /PBRST has an internal pull-up resistor to VCC (typ. 40kΩ) Guaranteed by design Note 7. /PBRST must be held low for a minimum of 20ms to guarantee a reset Note 8. VCC falling at 1.66mV/µs Note 9. ms ms TD = 0V Note 2. Note 6. ms 20 Note 1. Note 5. ms 1 /RST has an open drain output January 2006 3 MIC1232 MIC1232 Micrel, Inc. Timing Diagrams VCCTP VCC VCCTP tRPD RST tRPU RST Figure 1. Power-Up/Power-Down Sequence tST ST tTD Figure 2. Watchdog Input tPB tPDLY PBRST tRST RST RST Figure 3. Pushbutton Reset MIC1232 4 January 2006 MIC2755 Micrel, Inc. Applications Information Power Monitor The /RST and RST pins are asserted whenever VCC falls below the reset threshold voltage as determined by the TOL pin. A 5% tolerance level (4.62V reset threshold voltage) can be selected by connecting the TOL pin to ground and a 10% tolerance can be selected by connecting the TOL pin to VCC. The reset pins will remain asserted for a period of 250ms after VCC has risen above the reset threshold voltage. The reset function ensures the microprocessor is properly reset and powers up into a known condition after a power failure. /RST will remain valid with VCC as low as 1.4V. Watchdog Timer The microprocessor can be mounted by connecting the /ST pin (watchdog input) to a bus line or I/O line. If a high-to-low does not occur on the/ST pin within the watchdog timeout period (determined by the TD pin, see Table 1.), the /RST and the RST will remain asserted for 250ms when this occurs. A minimum pulse of 75ns or any transition high-to-low on the /ST pin will reset the watchdog timer. The watchdog timer will be reset if /ST sees a valid transition within the watchdog timeout period. Pushbutton Reset Input The /PBRST input can be driven with a manual pushbutton switch or with external logic signals. the input is internally debounced and requires an active low signal to force the reset outputs into their active states. The /PBRST input will recognize any pulse that is 20ms in duration or greater and will ignore all pulses that are less than 1ms in duration. Block Diagram VCC (8) TOL (3) PBRST (1) TRIP POINT SELECT + REF RESET GENERATOR - RST (5) MANUAL RESET DEBOUNCE ST (7) TD (2) January 2006 RST (6) WATCHDOG TIMER GND (4) TIMEOUT SELECT 5 MIC1232 MIC1232 Micrel, Inc. Package Information 0.400 0.370 0.260 0.240 0.310 0.290 0.150 0.120 0.035 0.015 0.150 0.125 0.023 0.015 0.370 0.300 0.110 0.090 8-Pin PDIP (N) 8-Pin SOIC (M) MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2000 Micrel, Inc. MIC1232 6 January 2006