MAX809 Series, MAX810 Series
Detail Operation Description
The MAX809/810 series microprocessor reset
supervisory circuits are designed to monitor the power
supplies in digital systems and provide a reset signal to the
processor without any external components. Figure 2 shows
the timing diagram and a typical application below. Initially
consider that input voltage V
CC
is at a nominal level greater
than the voltage detector upper threshold (
VTH
). And the
RESET
(RESET)
output voltage (Pin 2) will be in the high
state for MAX809, or in the low state for MAX 810 devices.
If there is an input power interruption and V
CC
becomes
significantly deficient, it will fall below the lower detector
threshold (V
TH−
). This event causes the RESET output to be
in the low state for the MAX809, or in the high state for the
NCP810 devices. After completion of the power
interruption, V
CC
will rise to its nominal level and become
greater than the V
TH
. This sequence activates the internal
oscillator circuitry and digital counter to count. After the
count of the timeout period, the reset output will revert back
to the original state.
Input Voltage
V
CC
V
TH+
V
TH–
V
CC
Reset Output
MAX809, NCP803
V
TH–
0V
Reset Output
MAX810
V
CC
V
TH–
0V
t
RP
Figure 15. Timing Waveforms
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