83CXXX Datasheet, PDF (5/6 Pages) Unisonic Technologies – 4-PIN μP VOLTAGE MONITORS WITH MANUAL RESET INPUT

83CXXX
Preliminary
CMOS IC
„ APPLICATION INFORMATION
1. Ensuring a Valid Reset Output Down to V_CC = 0
The UTC 83CXXX RESET output no more sinks current when V_CC drops below 1V—it becomes an open
circuit. Therefore, high-impedance CMOS logic input connected to RESET can drift to undetermined voltages. This
presents no problem in most applications since most microprocessors and other circuitry can’t be operated when V_CC
is under 1V. In figure 1, however, in applications where RESET must be valid down to 0V. In order to causes any
stray leakage currents to flow to ground, adding a pull-down resistor to RESET , that holding RESET low. (R1’s
value is not critical and the value 100kΩ is large enough not to load RESET and small enough to pull RESET to
ground).
2. Benefits of Highly Accurate Reset Threshold
Most microprocessor supervisor ICs has reset threshold voltages between 5% and 10% below the value of
nominal supply voltages. If using ICs rated at only the nominal supply ±5%, this leaves an uncertainty zone where
the supply is between 5% and 10% low and where the reset may or may not be asserted.
The UTC 83C308 with high accuracy ensure that the reset is asserted closely to 5% limit and long before the
supply has declined to 10% below nominal.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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QW-R502-353.a