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
Reset-clock off time
Reset low time
tON
tOFF
tRL
tRH
fH
●
●
●
●
▲ *2
●
Reset high time
●
●
●
Watchdog frequency high
Watchdog frequency low
Notes: 1. K = R2 / (R1 + R2)
●
●
fL
●
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
Calculation of RES Output Timing
Item
Formula
Notes
tON (ms)
tOFF (ms)
tRL (ms)
tRH (ms)
400 (Ω) × CR (µF)
1.99 × tRH (ms)
0.5 × tON (ms)
tON and tOFF can be set independently
tRL and tRH can be set independently
1.6 (V)
× CR (µF) × 103
K × 31 (µA) − 15.8 (µA)
tSL (ms)
≈ tOFF (ms)
Table 2
Calculation of Watchdog Frequency Range
Item
Formula
fH (MHz)
1
tRH (ms) − tRL (ms)
×
500 (Ω) × CF (µF)
t
RH (ms) + tRL (ms)
1
tRL (ms)
1
fL (Hz)
×
or
× 103
1.7 (MΩ) × CF (µF)
t
RH (ms) + tRL (ms)
tOFF (ms)
Whichever is larger
16
HITACHI-METALS [ HITACHI METALS, LTD ]
