LMX9820ASMX/NOPB National Semiconductor, LMX9820ASMX/NOPB Datasheet - Page 19

• Manufacturer Part Number: LMX9820ASMX/NOPB
• Description: MODULE BLUETOOTH SERIAL PORT SMD
• Manufacturer: National Semiconductor

Specifications of LMX9820ASMX/NOPB

• Frequency: 2.4GHz
• Data Rate - Maximum: 704kbps
• Modulation Or Protocol: Bluetooth v1.1, Class 2
• Applications: PDA's, POS Terminals
• Power - Output: 1dBm
• Sensitivity: -81dBm
• Voltage - Supply: 2.85 V ~ 3.6 V
• Current - Receiving: 65mA
• Current - Transmitting: 68mA
• Data Interface: PCB, Surface Mount
• Memory Size: 256Kb Flash
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 116-LTCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LMX9820ASMX; LMX9820ASMXTR

8.0 Digital Smart Radio
2. Crystal Pullability
Pullability is another important parameter for a crystal,
which is the change in frequency of a crystal with units of
ppm/pF, either from the natural resonant frequency to a
load resonant frequency or from one load resonant fre-
quency to another. The frequency can be pulled in a paral-
lel resonant circuit by changing the value of load
capacitance. A decrease in load capacitance causes an
increase in frequency, and an increase in load capacitance
causes a decrease in frequency.
3. Frequency Tuning
Frequency tuning is achieved by adjusting the crystal load
capacitance with external capacitors. It is a Bluetooth
requirement that the frequency is always within 20 ppm.
The crystal network or oscillator must have cumulative
accuracy specifications of 15 ppm to provide margin for
frequency drift with aging and temperature.
TEW Crystal
The LMX9820A has been tested with the TEW TAS-4025A
crystal, see Table 21 on page 19 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 starting point for
both Ct1 and Ct2. The 2480 MHz RF frequency offset is
then tested. Figure 11 on page 20 shows the RF frequency
offset test results.
Figure 11 on page 20 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 12 on page 20 shows the frequency offset test
results. The frequency offset is now zero with Ct1 = 10 pF,
Ct2 = 10 pF.
Reference Table 22 on page 19 for crystal tuning values
used on Austin Development Board with TEW crystal.
Figure 10. Crystal Equivalent Circuit
R1
C0
C1
(Continued)
L1
19
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
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