EM78P447SAM datasheet(26/55 Pages) EMC

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EM78P447S

OTP ROM

humidity, and leakage.

The smaller the Rext in the RC oscillator, the faster its frequency will be. On the contrary, for very low Rext values, for

instance, 1 K

Ω, the oscillator becomes unstable because the NMOS cannot discharge the current of the capacitance

correctly.

Based on the above reasons, it must be kept in mind that all of the supply voltage, the operation temperature, the

components of the RC oscillator, the package types, the way the PCB is layout, will affect the system frequency.

OSCI

EM 78P447S

VCC

Rext

Cext

Fig. 12 External RC Oscillator Mode Circuit

Table 11 RC Oscillator Frequencies

Cext

Rext

Average Fosc 5V,25

°C Average Fosc 3V,25°C

3.3k

4.32 MHz

3.56 MHz

5.1k

2.83 MHz

2.8 MHz

10k

1.62MHz

1.57 MHz

20 pF

100k

184 KHz

187 KHz

3.3k

1.39 MHz

1.35 MHz

5.1k

950 KHz

930 KHz

10k

500 KHz

490 KHz

100 pF

100k

54KHz

55 KHz

3.3k

580 KHz

550 KHz

5.1k

390 KHz

380 KHz

10k

200 KHz

300 pF

100k

21 KHz

<Note>

1. Measured on DIP packages.

2. For design reference only.

3.The frequency drift is about ±30%.

This specification is subject to change without prior notice.

06.25.2003 (V1.1)

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