M62001L/FP to M62008L/FP

Rev.1.00 Sep 14, 2005 page 6 of 9

Operating Principle

Description

In general, the memory backup function of a microcomputer, as shown in figure 1, uses two diodes to switch between

main power supply and backup power supply. The M62001 to M62008 are ICs that, in such memory backup operation,

INT

RESET

Microcomputer

system

Main power

supply

Backup

power

supply

INT

RESET

M62001

Figure 1

The ICs have an intelligent sequence such as substantial hysteresis action of

RESET toward normal state at restoration

of supply voltage, as well as two-step detection in low power dissipation mode.

Detailed Description

1. Two-step detection

The ICs perform two-step detection of supply voltage and have two output pins (

INT and RESET). Although they

have two comparators for two-step detection, they differ significantly from such that are simply provided with

independent detectors, because the

RESET output signal is dependent at power-up and the like upon the INT output

signal.

2.

INT output (Detection of 4.45 V and 4.25 V)

The

INT output at the power-up of supply voltage detects V

of the fact that the supply voltage has reached its normal level. When the supply voltage drops from its normal level

The microcomputer at this point enters sleep state and secures memory by a stop command issued by the

hysteresis voltage between themselves.

INT Output Voltage vs. Supply Voltage

5

0

4.04.2

4.44.6

4.85.0

2

4

1

3

Figure 2

INT Output (Detection of 4.45 V and 4.25 V)