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EM78P458/459
OTP ROM
3.3k 1.43 MHz 1.35 MHz
5.1k 980 KHz 877 KHz
10k 520 KHz 465 KHz
100 pF
100k 57 KHz 54 KHz
3.3k 510 KHz 470 KHz
5.1k 340 KHz 320 KHz
10k 175 KHz 170 KHz
300 pF
100k 19 KHz 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. 23 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
This specification is subject to change without prior notice. 07.01.2003 (V1.3)
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