4

■ BLOCK DESCRIPTION

1.

Comp. S

This function enables the MB3793 to detect an abnomality within 1

µs when the power is cut or falls abruptly.

2.

Output circuit

The output circuit contains a RESET output control comparator that compares the voltage at the CTP pin to the

threshold voltage to release the RESET output if the CTP pin voltage exceeds the threshold value.

Since the reset (RESET) output buffer has CMOS organization, no pull-up resistor is needed.

3.

Pulse generator

The pulse generator generates pulses when the voltage at the CK1 and CK2 clock pins changes to High from Low

level (positive-edge trigger) and exceeds the threshold voltage; it sends the clock signal to the watchdog timer.

4.

Watchdog timer

The watchdog timer can monitor two clock pulses. Short-circuit the CK1 and CK2 clock pins to monitor a single

clock pulse.

5.

Inhibition pin

The inhibition (INH) pin forces the watchdog timer on/off. When this pin is High level, the watchdog timer is stopped.

6.

Logic circuit

The logic circuit contains flip-flops.

Flip-flop RSFF2 turns on/off the circuit that accelerates charging of the power-on reset hold time setting capacitor

turned on.