ne56625-20 NXP Semiconductors, ne56625-20 Datasheet - Page 12

• Manufacturer Part Number: ne56625-20
• Description: Ne56625-20 System Reset With Watchdog Timer
• Manufacturer: NXP Semiconductors

Philips Semiconductors
APPLICATION INFORMATION
Detection threshold
The detection threshold voltage can be adjusted by externally
influencing the internal divider reference voltage. Figures 18 and 20
show a method to raise and lower the threshold voltage. Figures 19
and 21 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 Watchdog timer
T
V
V
CC
CC
Figure 20. Circuit to lower detection threshold.
Figure 18. 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
NMI
RESET
CLK
NMI
SL01588
SL01589
GND
GND
12
The Reset Detection Threshold can be increased by connecting an
external resistor R
See Figure 19 to determine the approximate value of R
threshold made be varied somewhat linearly from 2.4 V to 3.0 V.
The Reset Detection Threshold can be decreased by connecting an
external resistor R
Figure 21 to determine the approximate value of R
lower thresholds may be varied in a linear fashion from 1.85 V to
1.65 V.
Figure 19. Reset detection threshold versus external R
Figure 21. Reset detection threshold versus external R
3.1
3.0
2.9
2.8
2.7
2.6
2.5
2.4
2.3
1.9
1.8
1.7
1.6
200
200
T
amb
300
300
= 25 C
R
1
2
1
, EXTERNAL PIN 7 TO GROUND RESISTOR (k )
from Pin 7 to ground, as shown in Figure 18.
from Pin 7 to V
R
2
, EXTERNAL PIN 7 TO V
400
400
500
500
CC
V
V
SLR
SHR
, as shown in Figure 20. See
600
600
V
CC
NE56625-20
V
SLR
SHR
RESISTOR (k )
700
700
2
to use. The
T
amb
1
800
800
Product data
= 25 C
to use. The
SL01591
SL01590
1
2
900
900
.
.