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 V
DD
line.
V
DD
V
CC
INT
Main power
supply
Backup
power
supply
RESET
M62001
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 V
SH
(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 V
SL
(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, V
SH
the rise, and V
SL
the fall, of supply voltage, have a 100 mV
hysteresis voltage between themselves.
V
SH
– V
SL
≈
100 (mV)
INT
Output Voltage vs. Supply Voltage
5
4
3
V
SL
V
SH
INT
Output Voltage [Hold Type] (V)
2
1
0
4.0
4.2
4.4
4.6
4.8
5.0
Supply Voltage V
CC
(V)
Figure 2
INT
Output (Detection of 4.45 V and 4.25 V)
Rev.1.00 Sep 14, 2005 page 6 of 9
RENESAS [ RENESAS TECHNOLOGY CORP ]
