MIC706P/R/S/T, MIC708R/S/T Micrel, Inc. MIC706P/R/S/T, MIC708R/S/T µP Supervisory Circuit General Description Features The MIC705, MIC706, MIC707, and MIC708 are inexpensive mircoprocessor supervisory circuit that monitors power supplies in microprocessor based systems. The circuit functions include a watchdog timer, microprocessor reset, backup battery switchover, power failure warning and a debounced manual reset input. The MIC705 and MIC706 offer a watchdog timer function while the MIC707 and MIC708 have an active high reset output in addition to the active low reset output. Supply voltage monitor levels of 4.65V and 4.4V are available. The MIC705 and MIC707 have a nominal reset threshold level of 4.65V while the MIC706 and MIC708 have a 4.4V nominal threshold level. When the supply voltage drops below the respective reset threshold level, /RESET is asserted. • 30µA Maximum Supply Current • Debounced manual reset input is TTL/CMOS Compatible • Reset Pulse Width, 200ms • Watchdog timer, 1.6s (MIC706) • Precision supply voltage monitor • Early power fail warning or low battery detect Applications • • • • • • Laptop computers Intelligent systems Critical microprocessor power monitoring Printers Computers Controllers Ordering Information Part Number Temperature Range Package MIC70_ _NY –40ºC to +85ºC 8-Pin PDIP MIC70_ _MY –40ºC to +85ºC 8-Pin SOIC Standard Pb-Free MIC70_ _N MIC70_ _M Typical Application +3.0 or +3.3V (Regulated) Manual Reset VCC MR RESET VCC RESET MIC706 µP I/O Line NMI Interrupt WDI WDO PFO DC Voltage (Unregulated) PFI 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 MIC706P/R/S/T, MIC708R/S/T MIC706P/R/S/T, MIC708R/S/T Micrel, Inc. Pin Configuration MR 1 8 WDO VCC 2 7 RESET (RESET for MIC706P) GND 3 6 WDI PFI 4 5 PFO MR 1 8 RESET 7 RESET VCC 2 GND 3 PFI 4 MIC706 MIC708 6 NC 5 PFO 8-Pin PDIP Package 8-Pin SOIC Package Pin Description Pin Number MIC705/6 Pin Number MIC707/8 Pin Name 1 1 /MR Manual Reset Input forces /RESET to assert when pulled below 0.8V. An internal pull-up current of 250µA on this input forces it high when left floating. this input can also be driven from TTL or CMOS logic. 2 2 VCC Primary supply input, +5V 3 3 GND IC ground pin, 0V reference 4 4 PFI 5 5 /PFO Power Fail Output. The power fail comparator is independent of all other function on this device. 6 N/A WDI Watch Dog Input. The WDI input monitors microprcessor activity, an internal watchdog timer resets itself with each transition on the watchdog input. If the WDIpin is held high or low for longer than the watchog timeout period, /WDO is forced to active low. the watchdog function can be diabled by floating the WDI pin. N/A 6 N/C Not Internally Connected 7 7 /RESET 8 N/A /WDO N/A 8 RESET MIC706P/R/S/T, MIC708R/S/T Pin Function Power Fail Input. Internally connected to the power fail comparator which is referenced to 1.25V. The Power Fail Output (/PFO) remains high if PFI is above 1.25V. PFI should be connected to GND or VOUT if the power fail comparator is not used. /RESET is asserted if either VCCgoes below the reset threshold voltage or by low signal on the manual reset input (/MR). /RESET remains asserted for one reset timeout period (200ms) after VCC exceeds the reset threshold voltage or after the manual reset pin transition from low to high. The watchdog timer will not assert /RESET unless /WDO is connected to /MR Output for the Watchdog Timer. The watchdog timer resets itself with each transition o the watchdog input. If the WDI pin is held high or low for longer than the watchdog timeout period, /WDO is forced low. /WDO will also be forced low id VCC is below the reset threshold voltageand will remain low until VCC returns to a valid level. RESET is the compliment of /RESET and is asserted if either VCC goes below the reset threshold voltage or by a low signal on the manual reset input (/MR). RESET is suitable for microprocessor systems that use active high reset. 2 January 2006 MIC706P/R/S/T, MIC708R/S/T Micrel, Inc. Absolute Maximum Ratings(1) Operating Ratings(2) Terminal Voltage VCC ..........................................................–0.3V to +6.0V All other inputs .............................–0.3V to (VOUT + 0.3V) Input Current VCC, Gnd ................................................................ 25mA Output Current (all outputs) ........................................ 20mA Lead Temperature (soldering, 10 sec.) ...................... 300°C Storage Temperature ................................ –65°C to +150°C Operating Temperature Range MIC70_N ................................................ –40°C to +85°C MIC70_M ................................................ –40°C to +85°C Power Dissipation (PDIP) ........................................ 475mW Power Dissipation (SOP) ......................................... 400mW Electrical Characteristics(3) VCC = 2.70V to 5.5V for MIC70_P/R; VCC = 3.00V to 5.5V for MIC70_S; VCC = 3.15V to 5.5V for MIC70_T; TA = Operating Temperature Range, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted Parameter Conditions Min. Operating Voltage Range, VCC Typ. 1.4 Supply Current Reset Voltage Threshold MIC70_P/R MIC70_S MIC70_T 2.55 2.85 3.00 2.63 2.93 3.08 140 200 Reset Threshold Hysteresis Max Units 5.5 V 30 µA 2.70 3.00 3.15 V V V 20 Reset Pulse Width, tRS /RESET Output Voltage (MIC70_R/S/T) ISource = 200µA ISink = 1.2mA ISink = 50µA, VCC = 1.4V 0.8 × VCC RESET Output Voltage (MIC706P) ISource = 200µA ISink = 1.2mA 0.8 × VCC RESET Output Voltage (MIC708R/S/T) ISource = 200µA ISink = 500µA 0.8 × VCC Watchdog Timeout Period, tWD 1.0 WDI Minimum Input Pulse, tWP VIL = 0.4V, VIH = 80% of VCC VIL = 0.4V, VIH = 80% of VCC > 4.5V WDI Threshold Voltage VIH VIL 1.6 mV 280 ms 0.3 0.3 V V V 0.3 V V 0.3 V V 2.25 sec 100 50 ns ns 0.7 × VCC WDI Input Current WDI = 0V or VCC WDO Output Voltage ISource = 200µA ISink = 500µA -1 /MR Pull-Up Current /MR = 0V 20 /MR Pulse Width, tMR VCC = 4.5V 500 150 /MR Input Threshold VIL VIH 0.8 × VCC 250 0.6 V V 1 µA 0.3 V V 600 µA ns ns 0.7 × VCC /MR to Reset Output Delay, tMD 0.6 V V 750 ns PFI Input Threshold 1.2 1.25 1.3 V PFI Input Current -25 0.01 +25 nA 0.3 V V /PFO Output Voltage Note 1. ISink = 1.2mA ISource = 200µA 0.8 × VCC Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Specification for packaged product only. January 2006 3 MIC706P/R/S/T, MIC708R/S/T MIC706P/R/S/T, MIC708R/S/T Micrel, Inc. Timing Diagram Timing Diagram for Reset MIC706P/R/S/T, MIC708R/S/T 4 January 2006 MIC706P/R/S/T, MIC708R/S/T Micrel, Inc. Block Diagram VCC 250•A MR (1) RESET GENERATOR + VCC (2) VTHR* - RESET (7) (RESET for MIC706P) WDO (8) WATCHDOG TIMER WDI (6) + PFI (4) 1.25V PFO (5) - * 2.63, 2.93, or 3.08V MIC705/MIC706 Block diagram • V THR * 2.63, 2.93, or 3.08V MIC707/MIC708 Block Diagram January 2006 5 MIC706P/R/S/T, MIC708R/S/T MIC706P/R/S/T, MIC708R/S/T Micrel, Inc. Applications Information Watchdog Timer The microprocessor can be monitored by connecting the WDI pin (watchdog input) to a bus line or an I/O line. If a transition doesn't occur on the WDI pin with in the watchdog timeout (Table 1.), the microprocessor is reset. /RESET will remain asserted for 200ms when this occurs. A minimum pulse of 100ns or any transition low-to-high or high-to-low on the WDI pin will reset the watchdog timer. The output of the watchdog timer (WDO) will remain high, if WDI sees a valid transition within the watchdog period or if VCC falls below the reset threshold as the watchdog timer is disabled when this happens. Microprocessor Reset The /RESET pin is asserted whenever VCC falls below the reset threshold voltage. The reset pin remains asserted for a period of 200ms after VCC has risen above the reset threshold voltage. The reset timeout period can also be selected by the end user, see Table 1. The reset function ensures the microprocessor is properly reset and powers up into a known condition after a power failure. /RESET will remain valid with VCC as low as 1.4V and when auxiliary power is connected to VBATT (VBATT > 2.0V), the reset pin will remain valid with VCC from 0V to 5.5V. Power Fail Warning An additional comparator which is independent of the other functions on the MIC706P/R/S/T is provided for early warning of power failure. An external voltage divider can be used to compare unregulated DC to an internal 1.25V reference. The voltage divider ratio on the input of the power-fail comparator (PFI) can be chosen so as to trip the power fail comparator a few milliseconds before VCC falls below the maximum reset threshold voltage. The output of the power-fail comparator (/PFO) can be used to interrupt the microprocessor when used in this mode and execute shut-down procedures prior to power loss. Hysteresis can be added to this comparator with external resistors, as is commonly done with any comparator. When VCC < VBATT - 1.2V (typ.), the power-fail comparator is turned off and /PFO is pulled low in order to conserve power. Unregulated DC R1 PFI R2 + 1.25V - PFO Figure 1. Power Fail Comparator MIC706P/R/S/T, MIC708R/S/T 6 January 2006 MIC706P/R/S/T, MIC708R/S/T 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. MIC706P/R/S/T, MIC708R/S/T 7 January 2006