ULTRA-SMALL PACKAGE HIGH-PRECISION VOLTAGE DETECTOR
S-808xxC Series
Rev.3.2_00
VDD
VDD
Detection voltage
Release voltage
+
VDET) Max.
−
VDET) Max.
VDET) Min.
(
Detection voltage range
(
−
Release voltage range
( VDET) Min.
+
OUT
OUT
Figure 19 Detection Voltage (CMOS Output Products)
Figure 20 Release Voltage (CMOS Output Products)
Remark Although the detection voltage and release voltage overlap in the range of 1.514 V to 1.530 V,
+VDET is always larger than −VDET
2. 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 16). 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 13), taking a CMOS active
low product for example, the through-type current which is generated when the output goes from low to high
(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 low to high. A through-type current is again generated, a voltage drop appears, and repeating the
process finally induces oscillation.
VDD
RA
VIN
S-808xxCL
OUT
RB
VSS
Figure 21 An Example for Bad Implementation of Input Voltage Divider
Seiko Instruments Inc.
23
SII [ SEIKO INSTRUMENTS INC ]
