ha16117fpc Renesas Electronics Corporation., ha16117fpc Datasheet - Page 7

• Manufacturer Part Number: ha16117fpc
• Description: Cmos Watchdog Timer
• Manufacturer: Renesas Electronics Corporation.

Internal Operation and Usage Notes
Figure 3 shows an equivalent circuit of the watchdog timer block with a V
level of 0 V, and the following pages show internal operation timing charts for different P-RUN
frequencies. (Descriptions apply to conditions C
Operation
The power-on and auto-reset circuit is a multivibrator with timing controlled by C
discharge current I
on-duty is 25% or above, the C
is fixed low, and RES is not output. The (WD) on-duty varies according to the P-RUN frequency. If the
frequency is lower or higher than the design value, the (WD) on-duty decreases, and at 25% or below, RES
is output. Refer to the timing charts on the following pages for an explanation of the operation of the
watchdog filter.
Usage Notes
When the P-RUN frequency reaches 20 kHz or above, t
following pages). This must be borne in mind in the design stage.
If the P-RUN frequency fluctuates, RES may also be output within the normal detection set frequency
(see the timing charts on the following pages).
Detection frequencies f
dispersion can be expected. A margin of 30% or more should be allowed for in the design.
0.01
P-RUN
C
F
I
0.8
typ
w
2
. As I
1/2
frequency divider
D
Q
A
Watchdog filter circuit
Q
Q
1
H
: I
and f
Figure 3 Watchdog Timer Evaliation Circuit
2
Q
R
3.6 V
0.9 V
pin potential does not fall below 1.6 V. Therefore, (C) in the figure below
L
3 : 1 (Typ design value), when the (WD) (watchdog filter circuit output)
V
described in the Data Book are Typ values, and a certain amount of
CC
(5 V)
+
+
WD
F
= 0.01 F, C
0.1
B
Power-on and auto-reset circuit
OFF
C
is short (see the timing charts on the
R
R
= 0.1 F, R
I
I
10.7
typ
8
1
2
typ
3.2 V
1.6 V
CC
2
/(R
pin level of 5 V and ACC pin
+
1
+ R
HA16117F Series
Low voltage detection block
R
C
2
) = 0.6.)
charge current I
RES
1
and
7