S1002 Datasheet, PDF (15/39 Pages) Seiko Instruments Inc – VOLTAGE DETECTOR WITH SENSE PIN

Rev.1.1_00
VOLTAGE DETECTOR WITH SENSE PIN
S-1002 Series
3. Hysteresis width (V_HYS)
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 = V_HYS in "Figure 22 Timing Chart of S-1002 Series NA / NB Type" and "Figure
24 Timing Chart of S-1002 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. 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.
5. Oscillation
In applications where an input resistor is connected (Figure 20), 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 20, 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.
V_DD
R_A
V_IN
R_B
VDD
SENSE ^OUT
VSS
(CMOS output product)
GND
Figure 20 Example for Bad Implementation Due to Detection Voltage Change
Seiko Instruments Inc.
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