ASM813LCPA ALSC [Alliance Semiconductor Corporation], ASM813LCPA Datasheet - Page 5

• Manufacturer Part Number: ASM813LCPA
• Description: Low Power UP Supervisor Circuits
• Manufacturer: ALSC [Alliance Semiconductor Corporation]

RESET
RESET
WDO
WDI
rev 1.2
July 2004
transitions at WDI will reset the watchdog timer and initiate a
new countdown sequence.
WDO will also become LOW and remain so, whenever the
supply voltage, V
WDO goes HIGH as soon as V
threshold. There is no minimum pulse width for WDO as
there is for the RESET outputs. If WDI is floated, WDO
essentially acts as a low-power output indicator.
Figure 2: Watchdog Timing
Application Information
Ensuring That RESET is Valid Down to V
When V
no longer pulls down; it becomes indeterminate. To avoid the
possibility 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.
Bi-directional Reset Pin Interfacing
The ASM705/6/7/8 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.
CC
falls below 1.1V, the ASM705-708 RESET output
CC
, falls below the device threshold level.
Notice: The information in this document is subject to change without notice
CC
transitions above the
CC
Low Power µP Supervisor Circuits
= 0V
Supply Voltage
Monitoring Voltages Other Than V
The ASM705-708 can monitor voltages other than V
the Power Fail circuitry. If a resistive divider is connected
from the voltage to be monitored to the Power Fail input
(PFI), the PFO will go LOW if the voltage at PFI goes below
1.25V reference. Should hysteresis be desired, connect a
resistor (equal to approximately 10 times the sum of the two
resistors in the divider) between the PFI and PFO pins. A
capacitor between PFI and GND will reduce circuit sensitivity
to input high-frequency noise. If it is desired to assert a
RESET for voltages other than V
be connected to the MR.
Figure 3: Bi-directional Reset Pin Interfacing
Figure 4: Monitoring +5V and an additional supply V
V
IN
R
R
1
2
ASM705 / 706 / 707 / 708
ASM70x
V
GND
CC
RESET
PFI
Bi-directional I/O Pin
4.7kΩ
CC
V
+5V
ASM70X
CC
GND
then the PFO output is to
CC
RESET
RESET
Input
BUF
ASM813L
PFO
MR
µC or µP
GND
CC
IN
5 of 15
Buffered
RESET
To µP
using