IMP705/6/7/8, 813L
Application Information
Ensuring That RESET is Valid Down to VCC = 0V
Bi-directional Reset Pin Interfacing
The IMP705/6/7/8 can interface with µP/µC bi-directional reset
pins by connecting a 4.7kΩ resistor in series with the RESET
output and the µP/µC bi-directional RESET pin.
When VCC falls below 1.1V, the IMP705-708 RESET output no
longer pulls down; it becomes indeterminate. To avoid the possi-
bility that stray charges build up and force RESET to the wrong
state, a pull-down resistor should be connected to the RESET pin,
thus draining such charges to ground and holding RESET
low. The resistor value is not critical. A 100kΩ resistor will pull
RESET to ground without loading it.
BUF
Buffered
RESET
V
< 1.1V
CC
V
V
CC
CC
IMP70x
Power
Supply
IMP70x
µC or µP
4.7kΩ
RESET
Input
100k
RESET
RESET
GND
GND
GND
Bi-directional I/O Pin
(Example: 68HC11)
705_08.eps
705_06.eps
Figure 3. Ensuring That RESET is Valid Down to VCC = 0V
Figure 3. Bi-directional Reset Pin Interfacing
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© 1999 IMP, Inc.
6
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