CAT811_15 Datasheet, PDF (6/9 Pages) ON Semiconductor – 4-Pin Microprocessor Power Supply Supervisor

CAT811
DETAILED DESCRIPTION
Reset Timing
The reset signal is asserted LOW for the CAT811 when the power supply voltage falls below the threshold trip voltage and
remains asserted for at least 140 ms after the power supply voltage has risen above the threshold.
5V
V_CC
Threshold
Voltage
0V
5V
CAT811 RESET
0V
V_CC
CAT812 RESET
0V
140 ms
minimum
Reset
Timeout Period
Figure 6. Reset Timing Diagram
V_CC Transient Response
The CAT811 protect mPs against brownout failure. Short
duration transients of 4 ms or less and 100 mV amplitude
typically do not cause a false RESET.
Figure 7 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 0.5 V above the threshold and drops below
it by the amplitude of the overdrive voltage (V_TH − V_CC).
30
T_AMB = 25°C
25
Valid Reset with V_CC under 1.0 V
To ensure that the CAT811 RESET pin is in a known state
when V_CC is under 1.0 V, a 100 kW pull−down resistor
between RESET pin and GND is recommended; the value
is not critical.
Power
Supply
V_CC
CAT811
MR RESET
GND
100 kW
20
CAT811Z
15
CAT811M
10
Figure 8. RESET Valid with V_CC Under 1.0 V
5
0
1
10
100
1000
RESET OVERDRIVE V_TH − V_CC (mV)
Figure 7. Maximum Transient Duration without
Causing a Reset Pulse vs. Reset Comparator
Overdrive
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