Line Voltage Detector Circuit - Star Micronics TUP400 Series Technical Manual

2-5. +5V Line Voltage Detector Circuit
The voltage-detection IC detects momentary drops or unstable levels in the +5V line voltage.
The following illustrates the equivalence circuit of the voltage detector IC (Fig. 2-9 IC4).
The following operation timing chart shows control is performed by the voltage detector IC output. If the +5V line voltage
falls below 4.25V, the IC produces a reset signal from its OUT terminal, resetting the CPU and the gate array.
V
CC
1
SµA typ
R1
–
+
R2
1.25V
3
GND
Fig. 2-11 Equivalence Circuit for Voltage Detecting IC
V Voltage
CC
4.25V
0.8V
Output
Voltage
Fig. 2-12 Operation Timing Chart
–
4
Cd
td td
td = 0.34 Cd (pF) [µs]
– 25 –
5
OUT
t
t