Philips DVDR890 - Figure

Circuit-, IC Descriptions and List of Abbreviations
EN 182 DVDR880-890 /0X19.
NCP300, NCP301
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17
OPERATING DESCRIPTION
The NCP300 and NCP301 series devices are second
generation ultra–low current voltage detectors. Figures 21
and 22 show a timing diagram and a typical application.
Initially consider that input voltage V
in
is at a nominal level
and it is greater than the voltage detector upper threshold
(V
DET+
), and the reset output (Pin 1) will be in the high state
for active low devices, or in the low state for active high
devices. If there is a power interruption and V
in
becomes
significantly deficient, it will fall below the lower detector
threshold (V
DET–
). This sequence of events causes the Reset
output to be in the low state for active low devices, or in the
high state for active high devices. After completion of the
power interruption, V
in
will again return to its nominal level
and become greater than the V
DET+
. The voltage detector
has built–in hysteresis to prevent erratic reset operation as
the comparator threshold is crossed.
Although these device series are specifically designed for
use as reset controllers in portable microprocessor based
systems, they offer a cost–effective solution in numerous
applications where precise voltage monitoring is required.
Figure 22 through Figure 29 shows various application
examples.
Figure 21. Timing Waveforms
V
in
V
DET
+
V
DET–
Input Voltage, Pin 2
V
in
0 V
Reset Output (Active Low), Pin 1
Reset Output (Active High), Pin 1
V
in
0 V
V
DET
+
V
DET–
V
DET
+
V
DET–