MIC706P/R/S/T, MIC708R/S/ T
µP Supervisory Circuit
General Description
The MIC706 and MIC708 are inexpensive microprocessor
supervisory circuits that monitor power supplies in 3.0V
and 3.3V microprocessor-based systems. The circuit
functions include a watchdog timer, microprocessor reset,
power-failure warning, and a debounced manual reset
input.
The MIC706 offers a watchdog timer function, while the
MIC708 has an active-high reset output in addition to the
active-low reset output.
The R, S, and T versions a re similar in all respects ex cept
for supply voltage reset threshold levels. The threshold
levels are 2.63, 2.93, and 3.08V, respectively. When the
supply voltage drops below the reset threshold level,
/RESET (and RESET for the MIC708) is asserted.
The MIC706P is identical to the MIC706R, except that the
Reset output is asserted high.
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
Features
• Maximum supply current: 30µA
• Debounced manual reset input is TTL/CMOS
compatible
• Reset pulse width: 200ms
• Watchdog timer: 1.6s (MIC706)
• Precision supply voltage monitor
• Easy power-fail warn in g or lo w-battery detect
Applications
• Laptop and desktop computers
• Intelligent systems
• Critical microprocessor power monitoring
• Printers
• Controllers
Typical Ap plication
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
May 28, 2014 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Ordering Information
Part Number Threshold (V) /RESET RESET WDI Junction Temperature Range Package
MIC706PMY 2.63 √ √ –40°C to +85°C 8-Pin SOIC
MIC706RMY 2.63 √ √ –40°C to +85°C 8-Pin SOIC
MIC706SMY 2.93 √ √ –40°C to +85°C 8-Pin SOIC
MIC706TMY 3.08 √ √ –40°C to +85°C 8-Pin SOIC
MIC708RMY 2.63 √ √ –40°C to +85°C 8-Pin SOIC
MIC708SMY 2.93 √ √ –40°C to +85°C 8-Pin SOIC
MIC708TMY 3.08 √ √ –40°C to +85°C 8-Pin SOIC
Pin Configuration
MIC706
8-Pin SOIC (M)
(Top View)
MIC708
8-Pin SOIC (M)
(Top View)
Pin Description
Pin Number
MIC706 Pin Number
MIC708 Pin Name Pin Name
1 1 /MR Manual reset input forces reset outputs to assert when pulled below 0.8V. An
internal pul l-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
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 co mpar ator is not
used.
5 5 /PFO Power-Fail Output: The power-fail comparator is independent of all other function
on this device.
6 N/A WDI
Watchdog Inp ut. The WDI input monit or s microprocessor activity; an internal
watchdog timer resets itself with each transition on the watchdog input. If the WDI
pin is held high or low for longer than the watchdog timeout period, /WDO is forced
to active low. The watchdog function can be disabled by floating the WDI pin.
N/A 6 N/C Not internally connected.
May 28, 2014 2 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Pin Description (Continued)
Pin Number
MIC706 Pin Number
MIC708 Pin Name Pin Name
7 7 /RESET
/RESET is asserted if either VCC goes 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.
8 N/A /WDO
Output for the watchdog timer. The watchdog timer resets itself with each transition
to 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 if VCC
is below the reset threshold voltage and will remain low until VCC returns to a valid
level.
7
(MIC706P) 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.
May 28, 2014 3 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Absolute Maximum Ratings(1)
Terminal Voltage
VCC ......................................................... −0.3V to +6.0V
All Other Inputs. ........................... −0.3V to (VCC + 0.3V)
Input Current
VCC, GND .............................................................. 25mA
Output Current (All) ..................................................... 20mA
Lead Temperature (soldering, 10s) ............................ 300°C
Storage Temperature (TS) ......................... −65°C to +150°C
Operating Ratings(2)
Operating Temperature Range ................... –40°C to +85°C
Po we r D issipation (SOP) ......................................... 400mW
Thermal Resistance
8-Pin SOIC ....................................................... 150°C/W
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 Condition Min. Typ. Max. Units
Operating Voltage Range 1.4 5.5 V
Supply Current 30 µA
Reset Voltage Threshold
MIC70_P/R 2.55 2.63 2.70
V MIC70_S 2.85 2.93 3.00
MIC70_T 3.00 3.08 3.15
Reset Threshold Hysteresis 20 mV
Reset Pulse Width (tRS) 140 200 280 ms
/RESET Output Voltage (MIC70_R/S/T)
ISOURCE = 200µA 0.8 × VCC
V ISINK = 1.2mA 0.3
ISINK = 50µA, VCC = 1.4V 0.3
RESET Output Voltage (MIC706P) ISOURCE = 200µA 0.8 × VCC V
ISINK = 1.2mA 0.3
RESET Output Voltage (MIC708R/S/T) ISOURCE = 200µA 0.8 × VCC V
ISINK = 500µA 0.3
Watchdog Timeout Period (tWD) 1.0 1.6 2.25 s
WDI Minimum Input Pulse (tWP) VIL = 0.4V, VIH = 80% of VCC 100 ns
VIL = 0.4V, VIH = 80% of VCC > 4.5V 50
WDI Threshold Voltage VIH 0.7 × VCC V
VIL 0.6
WDI Input Current WDI = 0V or VCC −1 1 µA
WDO Output Voltage ISOURCE = 200µA 0.8 × VCC V
ISINK = 500µA 0.3
/MR Pull-Up Current /MR = 0V 20 250 600 µA
Notes:
1. Exceeding the absolute maximum ratings may damage the device.
2. The device is not guaranteed to functi on outside its operat i ng ratings.
3. Specific at i on for pack aged product only.
May 28, 2014 4 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Electrical Characteristics(3) (Continued)
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 Condition Min. Typ. Max. Units
/MR Pulse Width (tMR) VCC > 4.5V 500 ns
150
/MR Input Threshold VIL 0.6 V
VIH 0.7 × VCC
/MR-to-Reset Output Delay (tMD) 750 ns
PFI Input Threshold 1.2 1.25 1.3 V
PFI Input Current −25 0.01 +25 nA
/PFO Output Voltage ISINK = 1.2mA 0.3 V
ISOURCE = 200µA 0.8 × VCC
May 28, 2014 5 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Timing Diagram
Figure 1. Timing Diagram for Reset
May 28, 2014 6 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Block Diagram
MIC706 Block Diagram
MIC708 Block Diagram
May 28, 2014 7 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
Application Information
An additional comparator which is independent of the
other functions on the MIC706P and MIC708 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-f ail com par ator ( PFI) c an be chos e n s o
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 us ed t o i nter rupt t he microproces s or when used in
this mode and execute shutdown procedures prior to
power loss. Hysteresis can be added to this comparator
with external resistors, as is commonly done with any
comparator.
Figure 2. 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 within in the
watchdog timeout period, then /WDO will go low. A
minimum pulse of 100ns or any transition low-to-high or
high-to-low on the W DI pin will reset the watchdog timer.
The output of the w atc hd og timer (/WDO ) will r emain h ig h
if WDI sees a valid transition within the watchdog period.
If VCC falls b elow th e res et t hresho ld voltage, then /W DO
goes low immediately regardless of WDI. /WDO can be
connected to /MR to generate a reset pulse upon
watchdog timeout.
Mi cropro cessor Reset
The /RESET pin is asserted whenever VCC falls below
the reset threshold voltage or when /MR goes low. The
reset pin remains asserted for a period of 200ms after
VCC has risen above the reset threshold voltage and
/MR goes high. The reset function ensures the
microprocessor is properly reset and powers up into a
known c o ndi tio n af ter a po wer f ailur e. /RESET wil l re main
valid with VCC as low as 1.4V.
May 28, 2014 8 Revision 2.0
Micrel, Inc.
MIC706P/R/S/, MIC708R/S/T
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
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informat i on is not intended as a warranty and Micrel does not assume responsibility for its us e. Micrel reserves the right to change circuitry,
specificat i ons and descript i ons at any time without notice. No license, whether express , im plied, aris i ng by estoppel or otherwise, t o any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and condit i ons of sale for such products, Micrel assum es no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products includi ng liabi l ity or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyri ght or other intel l ect ual property right.
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ees to fully
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© 2000 Micrel, Incorporated.
May 28, 2014 10 Revision 2.0
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