4524_M Datasheet, PDF (240/310 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 720 FAMILY / 4500 SERIES

4524 Group
APPLICATION
2.8 Voltage drop detection circuit
2.8.1 Note on use
The voltage drop detection circuit detection voltage of this product is set up lower than the minimum value
of the supply voltage of the recommended operating conditions.
When the supply voltage of a microcomputer falls below to the minimum value of recommended operating
conditions and re-goes up (ex. battery exchange of an application product), depending on the capacity
value of the bypass capacitor added to the power supply pin, the following case may cause program failure
(Figure 2.8.3);
• supply voltage does not fall below to VRST, and
• its voltage re-goes up with no reset.
In such a case, please design a system which supply voltage is once reduced below to VRST and re-goes
up after that.
VDD
Recommended
operatng condition
min.value
VRST
No reset
Program failure may occur.
VDD
Recommended
operatng condition
min.value
VRST
Reset
→ Normal operation
Fig. 2.8.3 VDD and VRST
Rev.2.00 Aug, 06 2004
REJ09B0107-0200Z
2-76