MIC705MY(2014) View Datasheet(PDF) - Micrel
Part Name
Description
Manufacturer
MIC705MY Datasheet PDF : 10 Pages
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Micrel, Inc.
Application Information
Microprocessor 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 condition after
a power failure. /RESET will remain valid with VCC as low
as 1.4V.
Power-Fail Warning
An additional comparator which is independent of the
other functions on the MIC706/706/707/708 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 shutdown procedures prior to
power loss. Hysteresis can be added to this comparator
with external resistors, as is commonly done with any
comparator.
MIC705/706/707/708
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 the
watchdog timeout period, then /WDO will go low. A
minimum pulse of 50ns 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 left floating. If VCC falls below the reset threshold
voltage, then /WDO goes low immediately regardless of
WDI.
Figure 2. Power-Fail Comparator
September 15, 2014
8
Revision 2.1
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