CAT811, CAT812
DETAILED DESCRIPTIONS
RESET TIMING
The reset signal is asserted LOW for the CAT811 and
HIGH for the CAT812 when the power supply voltage
falls below the threshold trip voltage and remains asserted
for at least 140ms after the power supply voltage has
risen above the threshold.
Power 5V
Supply
Voltage 0V
Threshold
Voltage
Reset Timeout Period
140ms
minimum
RESET
5V
0V
5V
CAT811
RESET
0V
CAT812
Figure 1. Reset Timing Diagram
V
CC
TRANSIENT RESPONSE
The CAT811/812 protect
µPs
against brownout failure.
Short duration transients of 4µsec or less and 100 mV
amplitude typically do not cause a false RESET.
Figure 2 shows the maximum pulse duration of negative-
going V
CC
transients that do not cause a reset condition.
As the amplitude of the transient goes further below the
threshold (increasing V
TH
- V
CC
), the maximum pulse
duration decreases. In this test, the V
CC
starts from an
initial voltage of 0.5V above the threshold and drops
below it by the amplitude of the overdrive voltage (V
TH
- V
CC
).
30
TRANSIENT DURATION [µs)
25
20
15
10
5
0
1
10
CAT8xxM
TAMB = 25°C
CAT8xxZ
100
1000
RESET OVERDRIVE VTH - VCC [mV]
Figure 2. Maximum Transient Duration Without Causing a Reset Pulse vs. Reset Comparator Overdrive
Doc. No. 3005, Rev. R
6
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CATALYST [ CATALYST SEMICONDUCTOR ]
