PD62A_15 Datasheet, PDF (29/64 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLER FOR INFRARED REMOTE CONTROL TRANSMISSION

µPD62A
7. POC CIRCUIT (MASK OPTION)
The POC circuit monitors the power supply voltage and applies an internal reset in the microcontroller when the
battery is replaced, etc. If the application circuit satisfies the following conditions, the POC circuit can be
incorporated by the mask option.
• High reliability is not required.
• Clock frequency fX = 2.4 to 8 MHz
• Operating ambient temperature TA = –40 to +85˚C
Cautions 1. The one-time PROM product (µPD6P4B) already contains the POC circuit.
2. There are cases in which the POC circuit cannot detect a low power supply voltage of less
than 1 ms. Therefore, if the power supply voltage has become low for a period of less than
1 ms, the POC circuit may malfunction because it does not generate an internal reset signal.
3. Clock oscillation is stopped by the resonator due to low power supply voltage before the
POC circuit generates the internal reset signal. In this case, malfunction may result, for
example when the power supply voltage is recovered after the oscillation is stopped. This
type of phenomenon takes place because the POC circuit does not generate an internal reset
signal (because the power supply voltage recovers before the low power supply voltage is
detected) even though the clock has stopped. If, by any chance, a malfunction has taken
place, remove the battery for a short time and put it back. In most cases, normal operation
will be resumed.
4. If the application circuit does not satisfy the conditions above, design the application circuit
so that the reset takes effect without failure within the power supply voltage range by means
of an external reset circuit.
5. In order to prevent malfunction, be sure to input a low level to more than one of pins KI0 to
KI3 when reset is released (when the RESET pin changes from low level to high level, or POC
is released due to supply voltage startup).
Remarks 1. It is recommended that the POC circuit be incorporated when the application circuit is an infrared
remote-control transmitter for household appliances.
2. Even when a POC circuit is incorporated, the externally input RESET is valid with the OR condition;
therefore, the POC circuit and the RESET input can be used at the same time. However, if the
POC circuit detects a low power supply voltage, the RESET pin will be forced to low level; therefore,
use an N-ch open drain output or NPN open collector output for the external reset circuit.
Data Sheet U14474EJ2V0DS00
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