ULTRA-SMALL PACKAGE HIGH-PRECISION VOLTAGE DETECTOR
S-1000 Series
Rev.2.3_00
VDD
VDD
Release voltage
Detection voltage
(+VDET) Max.
(−VDET) Max.
(−VDET) Min.
Release voltage range
Detection voltage range
(+VDET) Min.
OUT
OUT
Figure 18 Detection voltage (CMOS output products)
2. Hysteresis width (VHYS
Figure 19 Release voltage (CMOS output products)
)
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 15). The existence of the hysteresis width prevents malfunction caused by
noise on input signal.
3. Through-type current
The through-type current refers to the current that flows instantaneously at the time of detection and release of a voltage
detector. The through-type current is large in CMOS output products, small in Nch open-drain output products.
4. Oscillation
In applications where a resistor is connected to the voltage detector input (Figure 20), taking a CMOS active “L” product
for example, the through-type current which is generated when the output goes from “L” to “H” (release) causes a voltage
drop equal to [through-type current] × [input resistance] across the resistor. When the input voltage drops below the
detection voltage (−VDET) as a result, the output voltage goes to low level. In this state, the through-type current stops
and its resultant voltage drop disappears, and the output goes from “L” to “H”. The through-type current is then
generated again, a voltage drop appears, and repeating the process finally induces oscillation.
VDD
RA
VIN
OUT
S-1000C
RB
VSS
Figure 20 An example for bad implementation of input voltage divider
16
Seiko Instruments Inc.
SII [ SEIKO INSTRUMENTS INC ]
