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| HA16117F Datasheet, PDF (17/31 Pages) Hitachi Semiconductor – CMOS Watchdog Timer | |||
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HA16117F Series
Selection of External Constants
If the reset duration necessary for the MPU to operate reliably at power-on is known, there is a simple
procedure for selecting external constants, starting from the power-on reset time (tON).
START
Set power-on
reset time tON
Set reset high
time tRH
Select external
constant CF
Check watchdog
frequency range
fH and fL
External
constant
values
⢠Decide reset
low time (tRL)
⢠Select external
constant CR
⢠Decide reset-clock
off time (tOFF)
⢠Select external
constants R1 and R2
Figure 4 Procedure for Selecting External Constants
Application Example
Battery
SW
5V
regulator
CF
0.01 µF
CR
0.1 µF
VCC
Tadj
P-RUN
ACC
HA16117F
CF
GND
CR
RES
R1
510 kâ¦
R2
750 kâ¦
VCC
Microprocessor
system
RES PORT GND
17
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