em78p257 ELAN Microelectronics Corp, em78p257 Datasheet - Page 49

• Manufacturer Part Number: em78p257
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

This specification is subject to change without prior notice.
4. RC Oscillator Mode with Internal Capacitor
Table 18 RC Oscillator Frequencies
Table 19 R Oscillator Frequencies
<Note>
If both precision and cost are taken into consideration, EM78P257A/B also offers a special oscillation mode,
which 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.
<Note>
100 pF
300 pF
20 pF
Cext
100k
300k
Rext
51k
1. Measured on DIP packages.
2. Design reference only
1. Measured on DIP packages.
2. Design reference only
3. The frequency drift about ±30%.
100k
100k
100k
Rext
3.3k
5.1k
3.3k
5.1k
3.3k
5.1k
10k
10k
10k
Fig. 21 Circuit for Internal C Oscillator Mode
Average Fosc 5V,25 C
EM78P257A/B
4.3 MHz
2.5 MHz
800KHz
OSCI
Average Fosc 5V,25 C
49
3.18 MHz
1.14 MHz
1.25 MHz
2.1 MHz
118 KHz
830 KHz
435 KHz
560 KHz
370 KHz
195 KHz
20 KHz
46KHz
Vcc
Rext
Average Fosc 3V,25 C
Average Fosc 3V,25 C
800 KHz
4.3 MHz
2.4 MHz
EM78P257
1.12 MHz
1.20 KHz
2.75MHz
121 KHz
815 KHz
440 KHz
545 KHz
360 KHz
195 KHz
2.0MHz
48 KHz
21 KHz
07.27.2004 (V1.4)
OTP ROM