BUILT-IN DELAY CIRCUIT (EXTERNAL DELAY TIME SETTING) VOLTAGE DETECTOR WITH SENSE PIN
Rev.2.1_01
S-1004 Series
3. Hysteresis width (VHYS
)
The hysteresis width is the voltage difference between the detection voltage and the release voltage (the voltage at
point B − the voltage at point A = VHYS in "Figure 23 Timing Chart of S-1004 Series NA / NB Type" and "Figure
25 Timing Chart of S-1004 Series CA / CB Type"). Setting the hysteresis width between the detection voltage
and the release voltage, prevents malfunction caused by noise on the input voltage.
4. Release delay time (tRESET
)
The release delay time is the time period from when the input voltage to the SENSE pin exceeds the release
voltage (+VDET) to when the output from the OUT pin inverts. The release delay time changes according to the
delay capacitor (CD).
VSENSE
+VDET
OUT
tRESET
Figure 20 Release Delay Time
5. Feed-through current
The feed-through current is a current that flows instantaneously to the VDD pin at the time of detection and release
of a voltage detector. The feed-through current is large in CMOS output product, small in Nch open-drain output
product.
6. Oscillation
In applications where an input resistor is connected (Figure 21), taking a CMOS output (active "L") product for
example, the feed-through current which is generated when the output goes from "L" to "H" (at the time of release)
causes a voltage drop equal to [feed-through current] × [input resistance]. Since the VDD pin and the SENSE pin
are shorted as in Figure 21, the SENSE pin voltage drops at the time of release. Then the SENSE pin voltage
drops below the detection voltage and the output goes from "H" to "L". In this status, the feed-through current stops
and its resultant voltage drop disappears, and the output goes from "L" to "H". The feed-through current is then
generated again, a voltage drop appears, and repeating the process finally induces oscillation.
VDD
RA
VIN
VDD
OUT
SENSE
VSS
CD
RB
(CMOS output product)
GND
Figure 21 Example for Bad Implementation Due to Detection Voltage Change
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