M62008L 데이터 시트보기 (PDF) - Renesas Electronics
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M62008L Datasheet PDF : 10 Pages
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M62001L/FP to M62008L/FP
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,
monitor in two steps each voltage on the VDD line.
Main power
supply
Backup
power
supply
VCC
INT
RESET
M62001
VDD
INT
RESET
Microcomputer
system
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 VSH (4.45 V/4.25 V) to inform the microcomputer system
of the fact that the supply voltage has reached its normal level. When the supply voltage drops from its normal level
to VSL (4.45 V/4.25 V) an interruption signal is output to alter the microcomputer system into RAM backup mode.
The microcomputer at this point enters sleep state and secures memory by a stop command issued by the
interruption signal. These detection voltage, VSH the rise, and VSL the fall, of supply voltage, have a 100 mV
hysteresis voltage between themselves.
VSH – VSL ≈ 100 (mV)
INT Output Voltage vs. Supply Voltage
5
4
3
VSL
VSH
2
1
0
4.0 4.2 4.4 4.6 4.8 5.0
Supply Voltage VCC (V)
Figure 2 INT Output (Detection of 4.45 V and 4.25 V)
Rev.1.00 Sep 14, 2005 page 6 of 9
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