THEORY OF OPERATION
2-5. +5V Line Voltage Detector Circuit
The voltage-detection IC (IC4 in Fig. 2-10) detects momentary drops or unstable levels in the +5V line voltage. IC4 operation is illustrated by the equivalence circuit shown below.
Fig. 2-11 Equivalence Circuit for Voltage Detecting IC
Fig. 2-11 shows the operational timing. If the +5V line voltage falls below 4.25V, the IC produces a reset signal at its OUTPUT terminal, resetting the CPU and the gate array.
VCC Voltage | |
4.25V | |
0.8V | t |
|
Output | |
Voltage | |
td | td |
| t |
| td = 0.34 × Cd (pF) [∝s] |
Fig. 2-12 Operation Timing Chart