ASM802LAEPA ALSC [Alliance Semiconductor Corporation], ASM802LAEPA Datasheet - Page 7

• Manufacturer Part Number: ASM802LAEPA
• Description: UP Power Supply Supervisor With Battery Backup Switch
• Manufacturer: ALSC [Alliance Semiconductor Corporation]

October 2003
Monitoring Capabilities Of The Power-fail Input:
Although designed for power supply failure monitoring, the
PFI pin can be used for monitoring any voltage condition that
can be scaled by means of a resistive divider. An example is
the negative power supply monitor configured in Figure 8. In
this case a good negative supply will hold the PFI pin below
1.25V and the PFO pin will be at logic “0”. As the negative
voltage declines, the voltage at the PFI pin will rise until it
exceeds 1.25V and the PFO pin will go to logic “1”.
rev 1.0
µP Power Supply Supervisor With Battery Backup Switch
Notice: The information in this document is subject to change without notice
Figure 8: Using PFI To Monitor Negative Supply Voltage
+5V
PFO
5 1.25
------------------ -
0V
+5V
–
R
1
V-
R
R
1
2
=
1.25 V
------------------------------ -
V
PFI
–
R
CC
2
TRIP
ASM690A
ASM692A
ASM802L
ASM802M
ASM805L
V
V-
GND
TRIP
ASM690A / 692A
ASM802L / 802M
PFO
V- = V
ASM805L
TRIP
0V
7 of 13