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

Part Name

Description

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HA16117

CMOS Watchdog Timer

Hitachi -> Renesas Electronics 

HA16117F Series

Setting of RES Timing and Watchdog Frequency Range

Different MPUs have different RES timing requirements. The minimum reset time (tON) required at power-

on (rise of VCC) is 20 ms for some MPUs and 100 ms for others.

RES timing waveform parameters must be selected according to the MPU. With the HA16117F the timing

of the RES output and the watchdog frequency range can both be set by external constants (CF, CR, and K).

Parameters

Item

Symbol

CR (pin 4)

CF (pin 3)

K (pin 8) *1

Power-on reset time

t ON

q

Reset-clock off time

t OFF

q

v *2

q

Reset low time

t RL

q

Reset high time

t RH

q

q

Watchdog frequency high fH

q

q

Watchdog frequency low

fL

q

q

q

Notes: 1. K = R2 / (R1 + R2)

2. Variability of tOFF increases with increasing CF. The variability ∆tOFF is approximately

3.3 (MΩ) × CF (µF), so CF ≤ 0.01 (µF) is recommended.

3. External constants should be selected with reference to the formulas in tables 1 and 2.

Table 1

Item

tON (ms)

tOFF (ms)

tRL (ms)

tRH (ms)

tSL (ms)

Calculation of RES Output Timing

Formula

400 (Ω) × CR (µF)

1.99 × tRH (ms)

0.5 × tON (ms)

K

×

31

1.6

(µA)

(V)

− 15.8

(µA)

×

CR

(µF)

×

103

≈ tOFF (ms)

Notes

tON and tOFF can be set independently

tRL and tRH can be set independently

Table 2

Item

fH (MHz)

fL (Hz)

Calculation of Watchdog Frequency Range

Formula

1

500 (Ω) × CF (µF)

×

tRH (ms) − tRL (ms)

tRH (ms) + tRL (ms)

1

1.7 (MΩ) × CF (µF)

×

tRL (ms)

tRH (ms) + tRL (ms)

or

1

tOFF (ms)

× 103

Whichever is larger

16

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