RFPIC12C509AG Microchip Technology Inc., RFPIC12C509AG Datasheet - Page 47

• Manufacturer Part Number: RFPIC12C509AG
• Description: 18/20-pin 8-bit Cmos Microcontroller With Uhf Ask/fsk Transmitter
• Manufacturer: Microchip Technology Inc.

8.2.3
For timing insensitive applications, the RC device
option offers additional cost savings. The RC oscillator
frequency is a function of the supply voltage, the resis-
tor (R
ing temperature. In addition to this, the oscillator
frequency will vary from unit to unit due to normal pro-
cess parameter variation. Furthermore, the difference
in lead frame capacitance between package types will
also affect the oscillation frequency, especially for low
C
variation due to tolerance of external R and C compo-
nents used.
Figure 8-4 shows how the R/C combination is con-
nected to the rfPIC12C509AG/509AF. For R
below 2.2 k , the oscillator operation may become
unstable, or stop completely. For very high R
(e.g., 1 M ) the oscillator becomes sensitive to noise,
humidity and leakage. Thus, we recommend keeping
R
Although the oscillator will operate with no external
capacitor (C
above 20 pF for noise and stability reasons. With no or
small external capacitance, the oscillation frequency
can vary dramatically due to changes in external
capacitances, such as PCB trace capacitance or pack-
age lead frame capacitance.
The Electrical Specifications sections show RC fre-
quency variation from part to part due to normal pro-
cess variation. The variation is larger for larger R (since
leakage current variation will affect RC frequency more
for large R) and for smaller C (since variation of input
capacitance will affect RC frequency more).
Also, see the Electrical Specifications sections for vari-
ation of oscillator frequency due to V
C
ating temperature for given R, C, and V
©
EXT
EXT
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2001 Microchip Technology Inc.
EXT
values. The user also needs to take into account
between 3 k
values as well as frequency variation due to oper-
) and capacitor (C
EXTERNAL RC OSCILLATOR
EXT
= 0 pF), we recommend using values
and 100 k .
EXT
) values, and the operat-
DD
for given R
DD
values.
EXT
EXT
values
values
EXT
Preliminary
/
rfPIC12C509AG/509AF
FIGURE 8-4:
C
V
R
EXT
SS
EXT
V
DD
EXTERNAL RC
OSCILLATOR MODE
OSC1
N
rfPIC12C509AG/509AF
DS70031A-page 45
Internal
clock