NE56604-42 Philips Semiconductors, NE56604-42 Datasheet - Page 11

• Manufacturer Part Number: NE56604-42
• Description: System reset
• Manufacturer: Philips Semiconductors

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Philips Semiconductors
Application information
The Watchdog timer’s external component values are critical to its
performance.
The detection threshold voltage can be adjusted by externally
influencing the internal divider reference voltage. Figures 21 and 23
show a method to lower and raise the threshold voltage. Figures 22
and 24 show the influence of the pull-down and pull-up resistors on
the threshold voltage. The use of a capacitor (1000 pF or larger)
from Pin 7 to ground is recommended to filter out noise from being
imposed on the threshold voltages.
2003 Oct 15
C
C
T
System reset with built-in Watchdog timer
T
V
V
CC
CC
Figure 21. Circuit to lower detection threshold.
Figure 23. Circuit to raise detection threshold.
1
2
3
4
1
2
3
4
8
7
6
5
8
7
6
5
1000 pF
1000 pF
R
1
R
2
LOGIC SYSTEM
LOGIC SYSTEM
RESET
CLK
RESET
RESET
CLK
RESET
SL01327
SL01328
GND
GND
11
The Reset Detection Threshold can be decreased by connecting an
external resistor R
Figure 22 to determine the approximate value of R
The Reset Detection Threshold can be increased by connecting an
external resistor R
See Figure 24 to determine the approximate value of R
5.0
4.0
3.5
3.0
Figure 22. Reset detection threshold vs. external R
5.1
5.0
4.9
4.8
4.7
4.6
4.5
4.4
4.3
Figure 24. Reset detection threshold vs. external R
0
0
V
T
amb
CC
= 5.0 V
100
100
= 25 C
R
1
2
2
, EXTERNAL PIN 7 TO GROUND RESISTOR (k )
from Pin 7 to V
from Pin 7 to ground, as shown in Figure 23.
R
1
, EXTERNAL PIN 7 TO V
200
200
300
300
CC
V
V
SL
SH
, as shown in Figure 21. See
400
400
CC
NE56604-42
V
V
SH
SL
RESISTOR (k )
500
500
1
to use.
V
T
amb
CC
2
600
600
Product data
= 5.0 V
= 25 C
to use.
SL01326
SL01325
1
2
.
.
700
700