EM78P458AP datasheet(48/76 Pages) EMC

48 / 76 page

EM78P458/459

OTP ROM

3.3k

510 KHz

470 KHz

5.1k

340 KHz

320 KHz

10k

175 KHz

170 KHz

300 pF

100k

19 KHz

<Note>

1. Measured on DIP packages.

2. Design reference only

4. RC Oscillator Mode with Internal Capacitor

If both precision and cost are taken into consideration, EM78P257A/B also offers a special oscillation

mode. It is equipped with an internal capacitor and an external resistor (connected to Vcc). The

internal capacitor functions as temperature compensator. In order to obtain more accurate frequency,

a precise resistor is recommended.

OSCI

EM78P458

Vcc

Rext

EM78P459

Fig. 21 Circuit for Internal C Oscillator Mode

Table 15 R Oscillator Frequencies

Rext

Average Fosc 5V,25

°C

Average Fosc 3V,25

°C

51k

2.22 MHz

2.17 MHz

100k

1.15 MHz

1.14 MHz

300k

375 KHz

370 KHz

<Note>

1. Measured on DIP packages.

2. Design reference only

4.13 Power-on Considerations

Any microcontroller is not warranted to start proper operation before the power supply stabilizes in

steady state.

EM78P458/459 POR voltage range is 1.2V~1.8V. Under customer application, when power is OFF,

Vdd must drop to below 1.2V and remains OFF for 10us before power can be switched ON again.

This way, the EM78P458/459 will reset and work normally. The extra external reset circuit will work

well if Vdd can rise at very fast speed (50 ms or less). However, under most cases where critical

This specification is subject to change without prior notice.

06.25.2004 (V1.4)

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