CAT811 Datasheet, PDF (7/11 Pages) Catalyst Semiconductor – 4-Pin Microprocessor Power Supply Supervisors

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
5V
RESET
0V
5V
RESET
0V
140ms
minimum
CAT811
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 VCC 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
25
TAMB = 25°C
20
15
CAT8xxZ
10
5
CAT8xxM
0
1
10
100
1000
RESET OVERDRIVE VTH - VCC [mV]
Figure 2. Maximum Transient Duration Without Causing a Reset Pulse vs. Reset Comparator Overdrive
Patent Pending
7
Doc. No. 3005, Rev. P