Line Voltage Detector Circuit - Star Micronics TSP200 Series Technical Manual

PRINCIPLES OF OPERATION
2-5. +5V Line Voltage Detector Circuit
The voltage-detection IC (IC3 in Fig. 2-13) detects momentary drops or unstable levels in the +5V line voltage. The
following shows an IC3-equivalent circuit.
Figure 2-15 shows the IC's operational timing. The IC asserts a reset signal at its output terminal when the -5V line voltage
falls below 4.25V, thereby resetting the CPU and the gate array.
V
CC
1
S A typ
R1
–
+
R2
1.25V
3
GND
Fig. 2-14 Equivalent Circuit, Voltage Detection IC
V Voltage
CC
4.25V
0.8V
Output
Voltage
Fig. 2-15 Operation Timing Chart
–
4
Cd
td td
td = 0.34 Cd (pF) [ s]
– 22 –
5
OUT
t
t