HA16117FPA RENESAS [Renesas Technology Corp], HA16117FPA Datasheet - Page 7

• Manufacturer Part Number: HA16117FPA
• Description: CMOS Watchdog Timer
• Manufacturer: RENESAS [Renesas Technology Corp]

HA16117F Series
Internal Operation and Usage Notes
Figure 3 shows an equivalent circuit of the watchdog timer block with a 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
current I
the C
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
Rev.3.00 Jun 15, 2005 page 7 of 30
When the P-RUN frequency reaches 20 kHz or above, t
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
be expected. A margin of 30% or more should be allowed for in the design.
R
pin potential does not fall below 1.6 V. Therefore, (C) in the figure below is fixed low, and RES is not output.
2
. As I
F
0.01
P-RUN
= 0.01 F, C
1
C
: I
I
0.8
typ
F
w
2
3 : 1 (Typ design value), when the (WD) (watchdog filter circuit output) on-duty is 25% or above,
1/2
frequency divider
H
R
D
Q
= 0.1 F, R
and f
A
Watchdog filter circuit
Q
Q
L
Figure 3 Watchdog Timer Evaliation Circuit
described in the Data Book are Typ values, and a certain amount of dispersion can
Q
3.6 V
0.9 V
2
V
/(R
CC
1
(5 V)
+
+
+ R
2
) = 0.6.)
WD
OFF
0.1
B
is short (see the timing charts on the following pages).
Power-on and auto-reset circuit
C
R
I
I
10.7
typ
8
1
2
CC
typ
3.2 V
1.6 V
pin level of 5 V and ACC pin level of 0 V,
R
charge current I
+
Low voltage detection block
C
1
and discharge
RES