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MIC705/06/07/08
Micrel, Inc.
MIC705/706/707/708
P Supervisory Circuit
General Description
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.
Features
* Debounced manual reset input is TTL/CMOS Compatible * Watchdog timer, 1.6s (MIC705/706) * 4.65V or 4.40V Precision Voltage Monitor * Early power fail warning or low battery detect
Applications
* * * * * * Automotive systems Intelligent systems Critical microprocessor power monitoring Battery powered computers Computers Controllers
Ordering Information
Part Number Standard MIC70_N MIC70_M Pb-Free MIC70_NY MIC70_MY Temperature Range -40C to +85C -40C to +85C Package 8-Pin PDIP 8-Pin SOIC
Typical Application
+5V (Regulated)
Manual Reset
VCC MR RESET
DC Voltage (Unregulated)
MIC705 MIC706
VCC RESET
P
PFI
WDI WDO PFO
I/O Line NMI Interrupt
Micrel, Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
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Pin Configuration
MR
VCC GND PFI
1 2 3 4
8
WDO RESET WDI
MIC705 MIC706
7 6 5
PFO
MR
VCC GND PFI
1 2 3 4
8
RESET RESET NC
MIC707 MIC708
7 6 5
PFO
8-Pin PDIP Package 8-Pin SOIC Package
Pin Description
Pin Number MIC705/06 1 Pin Number MIC707/08 1 Pin Name /MR Pin Function Manual Reset Input forces /RESET to assert when pulled below 0.8V. An internal pull-up current of 250A on this input forces it high when left floating. this input can also be driven from TTL or CMOS logic. Primary supply input, +5V IC ground pin, 0V reference 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. Power Fail Output. The power fail comparator is independent of all other function on this device. 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. Not Internally Connected /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.
2 3 4
2 3 4
VCC GND PFI
5 6
5 N/A
/PFO WDI
N/A 7
6 7
N/C /RESET
8
N/A
/WDO
N/A
8
RESET
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.
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Absolute Maximum Ratings(1)
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.) ...................... 300C Storage Temperature ................................ -65C to +150C
Operating Ratings(2)
Operating Temperature Range MIC70_N ................................................ -40C to +85C MIC70_M ................................................ -40C to +85C Power Dissipation (PDIP) ........................................ 475mW Power Dissipation (SOP) ......................................... 400mW
Electrical Characteristics(3)
VCC = 4.75V to 5.5V for MIC705/07; VCC = 4.5V to 5.5V for MIC706/08; TA = Operating Temperature Range, bold values indicate -40C TA +85C; unless noted Parameter Operating Voltage Range, VCC Supply Current Reset Voltage Threshold Reset Threshold Hysteresis Reset Pulse Width, tRS /RESET Output Voltage ISource = 80A ISink = 3.2mA MIC70_C, ISink = 50A, VCC = 1.4V ISource = 80A ISink = 3.2mA VIL = 0.4V, VIH = 80% of VCC VIH, VCC = 5V VIL, VCC = 5V WDI = 0V WDI = VCC ISource = 800A ISink = 1.2mA /MR = 0V VIL VIH VCC = 5V ISink = 3.2mA VCC = 5V, ISource = 800A 140 VCC - 1.5V Conditions MIC70_ MIC70_ MIC705, MIC707 MIC706, MIC708 4.50 4.25 4.65 4.4 40 200 280 0.4 0.3 0.4 1.6 2.25 Min. 1.4 Typ. Max 5.5 60 4.75 4.5 Units V A V V mV ms V V V V V sec ns 0.8 -50 50 150 0.4 250 600 0.8 250 1.2 -25 VCC - 1.5V 1.25 0.01 1.3 +25 0.4 V V A A V V A ns V V ns V nA V V
RESET Output Voltage Watchdog Timeout Period, tWD WDI Minimum Input Pulse, tWP WDI Threshold Voltage WDI Input Current WDO Output Voltage /MR Pull-Up Current /MR Pulse Width, tMR /MR Input Threshold /MR to Reset Output Delay, tMD PFI Input Threshold PFI Input Current /PFO Output Voltage
Note 1. Note 2. Note 3.
VCC - 1.5V 1.0 50 3.5 -150 VCC - 1.5V 100 150 2.0
Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Specification for packaged product only.
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Timing Diagram
Timing Diagram for Reset
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Block Diagrams
* 4.4V for MIC706
MIC705/MIC706 Block diagram
* 4.4V for MIC708
MIC707/MIC708 Block diagram
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Micrel, Inc. Power Fail Warning An additional comparator which is independent of the other functions on the MIC691/693 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
Applications Information
Battery Switchover Section The MIC691/693 monitors the supply voltage applied to the VCC pin. Whenever VCC falls below the reset threshold voltage and VBATT, the device enters battery-backup mode. When this happens, the auxiliary supply on VBATT is routed through a low impedance PMOS switch to the VOUT pin. The VOUT pin is capable of sourcing up to 25mA when in the backup mode. VCC is routed to VOUT through a large PMOS switch during normal operation (VCC > VBATT) and can source continuous currents of up to 250mA. VOUT can be used to drive CMOS RAM. The BATT ON Pin can be used to indicate the status of battery backup mode or as the base drive for an external pass transistor when VOUT has to source more than 25mA in battery-backup mode. VCC is connected to VOUT and the substrate whenever VCC exceeds the reset threshold. If VBATT is connected to a voltage source that is greater than 0.6V above VCC, the parasitic diode of the VBATT switch will conduct from the VBATT to the substrate. 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. Chip Enable Gating The MIC691/693 also include memory protection circuitry which inhibits the writing of memory during a power fail condition. During normal operation, chip enable transitions are gated througha series transmission gate from /CE IN to /CE OUT. The typical propagation delay through the chip enable gating circuitry is 2ns. /CE OUT follows /CE IN unless VCC drops below the reset threshold voltage, at which time /CE OUT will remain high until VCC returns to a valid level. EEPROMs can be write protected in a similar manner by connecting the /CE OUT pin to the store or write input.
R1
PFI
+
1.25V
R2
-
PFO
Power Fail Comparator 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.
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Package Information
0.400 0.370
0.260 0.240
0.310 0.290 0.035 0.015 0.150 0.125 0.110 0.090 0.370 0.300 0.150 0.120
0.023 0.015
8-Pin PDIP (N)
8-Pin SOIC (M)
MICREL INC.
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
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. (c) 2000 Micrel, Inc.
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