HA16103FPJ Datasheet, PDF (6/19 Pages) Renesas Technology Corp – Watchdog Timer

HA16103FPJ/FPK
Watchdog Timer Function
The system contains a bandpass filter for pulse width detection, which outputs a reset pulse when input pulses are not at
the preselected frequency (at either a higher or lower frequency).
The RC characteristic of the bandpass filter may be set with external components Rf and Cf. Equation 3 specifies how
to determine the minimum pulse width (tmin) for runaway detection of the bandpass filter, and figure 4 shows the
characteristic of the filter.
HA16103
Rf Cf
tmin = Cf x Rf x 0.11 (s) ⋅ ⋅ ⋅ ⋅ Equation 3
Rf : Ω
2.0 m
1.8 m
1.6 m
1.4 m
(Ta = 25°C)
P—Run pulse duty ratio 50% (fixed)
V_CC = 12 V
C_R = 0.1 µF
R_R = 180 k Ω
1.2 m
1.0 m
0.8 m
0.6 m
Cf = 0.022 µF
0.4 m
0.2 m
Cf = 0.01 µF
Cf = 0.0047 µF
100 k
200 k
Resistance Rf (Ω)
500 k
Figure 4 Characteristic of Power-On Reset Circuit
Rev.3.00 Jun 15, 2005 page 6 of 18