NE56625-20 Ver la hoja de datos (PDF) - Philips Electronics
Número de pieza
componentes Descripción
Fabricante
NE56625-20 Datasheet PDF : 15 Pages
| |||
Philips Semiconductors
System reset with Watchdog timer
Product data
NE56625-20
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.
VCC
1
2
3
CT
4
8
7
6
5
1000 pF
LOGIC SYSTEM
RESET
CLK
NMI
GND
R2
SL01588
Figure 18. Circuit to raise detection threshold.
VCC
1
2
3
CT
4
R1
8
7
6
5
1000 pF
LOGIC SYSTEM
RESET
CLK
NMI
GND
SL01589
Figure 20. Circuit to lower detection threshold.
The Reset Detection Threshold can be increased by connecting an
external resistor R1 from Pin 7 to ground, as shown in Figure 18.
See Figure 19 to determine the approximate value of R1 to use. The
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 R2 from Pin 7 to VCC, as shown in Figure 20. See
Figure 21 to determine the approximate value of R2 to use. The
lower thresholds may be varied in a linear fashion from 1.85 V to
1.65 V.
3.1
Tamb = 25 °C
3.0
2.9
2.8
2.7
2.6
VSHR
2.5
VSLR
2.4
2.3
200 300
400
500
600
700
800
900
R1, EXTERNAL PIN 7 TO GROUND RESISTOR (kΩ)
SL01590
Figure 19. Reset detection threshold versus external R1.
1.9
Tamb = 25 °C
VSHR
1.8
VSLR
1.7
1.6
200
300
400
500
600
700
800
900
R2, EXTERNAL PIN 7 TO VCC RESISTOR (kΩ)
SL01591
Figure 21. Reset detection threshold versus external R2.
2003 Oct 15
12
Share Link: 