EM78P259N/260N
8-Bit Microprocessor with OTP ROM
Based on the above reasons, it must be kept in mind that all supply voltage, the
operation temperature, the components of the RC oscillator, the package types, and
the way the PCB is layout, have certain effect on the system frequency.
The RC Oscillator frequencies:
Cext
Rext
3.3k
Average Fosc 5V,25°C
Average Fosc 3V,25°C
3.5 MHz
2.5 MHz
1.30 MHz
140 KHz
1.27 MHz
850kHz
450kHz
48kHz
3.2 MHz
2.3 MHz
1.25 MHz
140kHz
1.21 MHz
820kHz
450kHz
50kHz
5.1k
10k
20 pF
100k
3.3k
5.1k
10k
100 pF
300 pF
100k
3.3k
5.1k
10k
560kHz
370kHz
196kHz
20kHz
540kHz
360kHz
192kHz
20kHz
100k
NOTE: 1. Measured on DIP packages
2. Design reference only
3. The frequency drift is about ±30%
6.11.4 Internal RC Oscillator Mode
EM78P259N/260N offers a versatile internal RC mode with default frequency value of
4MHz. Internal RC oscillator mode has other frequencies (1MHz, 8MHz, and 455kHz)
that can be set by CODE OPTION (WORD1), RCM1, and RCM0. The Table below
describes the EM78P259N/260N internal RC drift with voltage, temperature, and
process variation.
Internal RC Drift Rate (Ta=25℃, VDD=5V±5%, VSS=0V)
Drift Rate
Internal
RC Frequency
Temperature
(-40℃~+80℃)
Voltage
Process
Total
(2.3V~5.5V)
4MHz
8MHz
±10%
±10%
±10%
±10%
±5%
±6%
±5%
±5%
±4%
±4%
±4%
±4%
±19%
±20%
±19%
±19%
1MHz
455MHz
Theoretical values, for reference only. Actual values may vary depending on the actual process.
64 •
Product Specification (V1.0) 06.16.2005
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
