LMX9820ASM NSC [National Semiconductor], LMX9820ASM Datasheet - Page 20

• Manufacturer Part Number: LMX9820ASM
• Description: Bluetooth Serial Port Module
• Manufacturer: NSC [National Semiconductor]

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8.0 Digital Smart Radio
TEW Crystal
The LMX9820A has been tested with the TEW TAS-4025A
crystal, see Table 21 on page 20 for specification.
Because the internal capacitance of the crystal circuit is 8
pF and the load capacitance is 16 pF, 12 pF is a good start-
ing point for both Ct1 and Ct2. The 2480 MHz RF fre-
quency offset is then tested. Figure 12 on page 21 shows
the RF frequency offset test results.
Figure 12 on page 21 shows the results are -20 kHz off the
center frequency, which is -1 ppm. The pullability of the
crystal is 2 ppm/pF, so the load capacitance must be
decreased by about 1.0 pF. By changing Ct1 or Ct2 to
10 pF, the total load capacitance is decreased by 1.0 pF.
Figure 13 on page 21 shows the frequency offset test
resuts. The frequency offset is now zero with Ct1 = 10 pF,
Ct2 = 10 pF.
Reference Table 22 on page 20 for crystal tuning values
used on Austin Development Board with TEW crystal.
(Continued)
20
Package
Frequency
Mode
Stability
C
ESR
C
Drive Level
Pullability
Storage Temperature
L
0
Load Capacitance
Shunt Capacitance
Reference
Specification
Ct1
Ct2
Table 22. TEW on Arizona Board
Table 21. TEW TAS-4025A
4.0 x 2.5 x 0.65 mm (4 pads)
12.000 MHz
Fundamental
>15 ppm @ -40 to +85°C
16 pF
80 max.
5 pF
50 ±10uV
2 ppm/pF min
-40 to +85°C
LMX9820A
10 pF
10 pF
Value
Revision 1.0