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 KΩ, 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.
VCC
Rext
OSCI
Cext
EM78P447S
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
5.1k
10k
100k
3.3k
5.1k
10k
100k
3.3k
5.1k
10k
4.32 MHz
2.83 MHz
1.62MHz
184 KHz
1.39 MHz
950 KHz
500 KHz
54KHz
580 KHz
390 KHz
200 KHz
21 KHz
3.56 MHz
2.8 MHz
1.57 MHz
187 KHz
1.35 MHz
930 KHz
490 KHz
55 KHz
550 KHz
380 KHz
200 KHz
21 KHz
20 pF
100 pF
300 pF
100k
<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.
26
06.25.2003 (V1.1)
ELAN [ ELAN MICROELECTRONICS CORP ]
