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參數資料
| 型號： | LMX9820 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Bluetooth Serial Port Module |
| 中文描述： | 藍牙串行端口模塊 |
| 文件頁數： | 17/40頁 |
| 文件大小： | 567K |
| 代理商： | LMX9820 |
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Revision 1.0
17
www.national.com
L
performance. Crystal load capacitance (C
L)
is calculated as
the following:
C
L
= C
int
+ Ct1//Ct2
The C
L
above does not include the crystal internal self-
capacitance C0 as shown in Figure 11 on page 17, so the
total capacitance is:
C
total
= C
L
+ C0
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.
Crystal/oscillator must have cumulative accuracy specifica-
tions of +15 ppm to provide margin for frequency drift with
ageing and temperature.
4. Vite Crystal
The VXE4-1055 is a 12 MHz SMT crystal from Vite.
National is using this crystal with the LMX9820. Table 21
on page 17 shows the specification of VXE4-1055.
Since the internal capacitance of the crystal circuit is 4-5 pF
and the load capacitance is 9 pF, 10 pF is a good starting
point for both Ct1 and Ct2. The 2480 MHz RF frequency
offset is then tested. Figure 12 on page 18 shows the RF
frequency offset test results.
Figure 12 shows the results are 100 kHz off the center fre-
quency, which is –4 ppm. The pullability of the crystal is 24
ppm/pF, so the load capacitance must be decreased by
about 0.2 pF. By changing Ct1 or Ct2 to 9 pF, the total load
capacitance is increased by 0.26 pF. Figure 13 shows the
frequency offset test resuts. The frequency offset is now
zero with Ct1 = 9 pF, Ct2 = 10 pF.
5. Kinseki KSS CX-4025S
The LMX9820 has also been tested with the Kineski KSS
CX-4025S. See Table 22 on page 17.
Figure 10. LMX9820 Crystal Recommended
Circuit
Figure 11. Crystal Equivalent Circuit
XTL_G
XTL_D
Ct1
Ct2
Crystal
R1
C1
L1
C0
Table 21. VXE4-1055-12M000
Specification
Value
Package
6.0x3.5x1.1 mm - 4 pads
Frequency
12.000 MHz
Mode
Fundamental
Stability
±18 ppm at -20 to +70°C (in-
clusive of all conditions)
Load Capacitance
9 pF
ESR
40
max, 20
typ
Shunt Capacitance
7 pF max
Drive Level
10 to 100 μW
Pullability
24 ppm/pF min
Storage Temperature
-40 to +85°C
Table 22. KSS CX-4025S
Specification
Value
Package
4.0x2.5x0.75 mm - 4 pads
Frequency
12.000 MHz
Mode
Fundamental
Stability
±20 ppm at -30 to +80°C (in-
clusive of all conditions)
Load Capacitance
12pF
ESR
80
max, 20
typ
Shunt Capacitance
3 pF max
Drive Level
100 μW max
Storage Temperature
-40 to +85°C
相關PDF資料 |
PDF描述 |
|---|---|
| LMX9820SB | Bluetooth Serial Port Module |
| LMX9820SBX | Bluetooth Serial Port Module |
| LP3882ESX-1.2 | 1.5A Fast-Response Ultra Low Dropout Linear |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMX9820A | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Bluetooth Serial Port Module |
| LMX9820ADEV | 制造商:Texas Instruments 功能描述:KIT DEV FOR LMX9820 |
| LMX9820ADONGLE/NOPB | 制造商:Texas Instruments 功能描述:KIT REF DESIGN FOR LMX9820 |
| LMX9820ASM | 制造商:Texas Instruments 功能描述:BLUETOOTH MODULE, SMD, 9820, FR4129 |
| LMX9820ASM/NOPB | 制造商:Texas Instruments 功能描述:IC MODULE BLUETOOTH 116-LTCC |
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