HA16103FPJ Datasheet, PDF (13/19 Pages) Renesas Technology Corp – Watchdog Timer

HA16103FPJ/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
++
−–
GND
Figure 7 RES Comparator
RES
Rev.3.00 Jun 15, 2005 page 13 of 18