HA16117 View Datasheet(PDF) - Hitachi -> Renesas Electronics

Part Name

Description

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HA16117

CMOS Watchdog Timer

Hitachi -> Renesas Electronics 

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 kΩ

R2

750 kΩ

VCC

Microprocessor

system

RES PORT GND

17

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