88CXX Datasheet, PDF (9/16 Pages) Unisonic Technologies – BUILT-IN DELAY CIRCUIT HIGH-PRECISION VOLTAGE DETECTOR

88CXX
CMOS IC
OPERATION
1. Basic operation: CMOS active low output
(1) When power supply voltage V_DD is greater than the release voltage +V_DET, the Nch transistor is OFF and the
Pch transistor ON, causing V_DD (high) to appear at the output.
(2) When power supply voltage V_DD goes below +V_DET, the output maintains the power supply voltage level, as
long as V_DD remains above the detection voltage -V_DET. When V_DD does fall below -V_DET (A in Figure 7), the Nch
transistor goes ON the Pch transistor goes OFF, and V_SS appears at the output.
(3) When V_DD falls below the minimum operating voltage, the output becomes undefined. However, output will
revert to V_DD if a pull-up has been employed.
(4) V_SS will again be output when V_DD rises above the minimum operating voltage. V_SS will continue to be output
even when V_DD surpasses -V_DET, as long as it does not exceed the release voltage +V_DET.
(5) When V_DD rises above +V_DET (B in Figure 7), the Nch transistor goes OFF the Pch transistor goes ON, and V_DD
appears at the output. Then V_DD at the OUT terminal appears with delay time (td) due to delay circuit.
VDD
(1) (2) (3) (4) (5)
VDD
RA
+
-
RB
VREF ^RC
N
Delay
circuit
CD
*
Pch
*
Nch
Hysteresis
width(VHYS)
A
OUT
VDD
B
Release voltage (+VDET)
Detection voltage (-VDET)
Min.operating voltage
Vss
Vss
CD ^{*Parasitic diode}
CD
2. Delay circuit
Figure 6
OUT terminal output
Vss
td
Figure 7


The delay circuit outputs the signal delayed from the release voltage (+V_DET) point of the power voltage V_DD
rising. The output signal is not delayed when the V_DD goes down the detection voltage (-V_DET) or less. (See Figure 7).
The delay time (td) is determined by the time constant of the built-in constant current (approx. 100nA in the case
of products with detection voltage of 1.5V or more, approx. 570nA in the case of products with detection voltage of
1.4V or less) and the attached external capacitor (C_D), and calculated from the following formula.
td (ms) = Delay factor×C_D (nF)
Delay factor: (25Ċ)
Products with detection voltage of 1.4V or less: Min.0.57, Typ.0.77, Max.0.96
Products with detection voltage of 1.5V or more: Min.3.8, Typ. 5.1, Max.6.4
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
9
QW-R502-040,A