HA16103 Datasheet, PDF (15/21 Pages) Hitachi Semiconductor – Watchdog Timer

HA16103 FPJ/FPK
Precautions
If the IC’s ground potential varies suddenly by several volts due to wiring impedance (see figure 6), a false
RES pulse may be output. The reason for this is that potentials in the RES pulse generating circuit change
together with the V_OUT-GND potential. The reference potential of the comparator in figure 7 and the
potential of the external capacitor have different impedances as seen from the comparator, causing a
momentary inversion. The solution is to stabilize the ground potential. Two ways of stabilizing the IC’s
ground line are:
• Separate the IC’s ground line from highcurrent ground lines.
• Increase the capacitance (Co) used to smooth the V_OUT output.
Wiring impedance
SW1
V _IGN
SW2
HA16103PJ/FPJ ^Co
R_L
Wiring impedance
Relay or other load
Figure 6 Typical Circuit
Vout
V _CC Vcont
Wiring impedance
C_RES
+
–
RES
GND
Figure 7 RES Comparator
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