Si4021
24
CRYSTAL SELECTION GUIDELINES
The crystal oscillator of the Si4021 requires a 10 MHz parallel mode crystal. The circuit contains an integrated load capacitor in order to
minimize the external component count. The internal load capacitance value is programmable from 8.5 pF to 16 pF in 0.5 pF steps. With
appropriate PCB layout, the total load capacitance value can be 10 pF to 20 pF so a variety of crystal types can be used.
When the total load capacitance is not more than 20 pF and a worst case 7 pF shunt capacitance (C
0
) value is expected for the crystal, the
oscillator is able to start up with any crystal having less than 100 ohms ESR (equivalent series loss resistance). However, lower C
0
and ESR
values guarantee faster oscillator startup. It is recommended to keep the PCB parasitic capacitances on the XTL pin as low as possible.
The crystal frequency is used as the reference of the PLL, which generates the RF carrier frequency (f
c
). Therefore f
c
is directly proportional to
the crystal frequency. The accuracy requirements for production tolerance, temperature drift and aging can thus be determined from the
maximum allowable carrier frequency error.
Maximum XTAL Tolerances Including Temperature and Aging [ppm]
Bit Rate:
2.4 kbps
30
60
90
120
150
180
210
433 MHz
20
50
75
100
100
100
100
868 MHz
10
25
40
60
75
100
100
915 MHz
10
25
40
50
75
75
100
Bit Rate:
9.6 kbps
30
60
90
120
150
180
210
433 MHz
15
50
75
100
100
100
100
868 MHz
8
25
40
60
75
75
100
915 MHz
8
25
40
50
70
75
100
Bit Rate:
38.4 kbps
30
60
90
120
150
180
210
433 MHz
don't use
20
50
75
100
100
100
868 MHz
don't use
10
30
40
60
75
100
915 MHz
don't use
10
25
40
60
75
75
Bit Rate:
115.2 kbps
30
60
90
120
150
180
210
433 MHz
don't use
don't use
don't use
don't use
30
50
100
868 MHz
don't use
don't use
don't use
don't use
20
30
50
915 MHz
don't use
don't use
don't use
don't use
15
30
50
Transmitter Deviation [+/- kHz]
Transmitter Deviation [+/- kHz]
Transmitter Deviation [+/- kHz]
Transmitter Deviation [+/- kHz]
Whenever a low frequency error is essential for the application, it is possible to pull the crystal to the accurate frequency by changing the
load capacitor value. The widest pulling range can be achieved if the nominal required load capacitance of the crystal is in the midrange ,
for example 16 pF. The pull-ability of the crystal is defined by its motional capacitance and C
0
.
Note:
? There may be other requirements for the TX carrier accuracy with regards to the requirements as defined by standards and/or
channel separations.
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
SI4022-A0-FT
IC TX FSK UNI 868/915MHZ 16TSSOP
SI4711-B30-GM
IC TX FM RADIO 76-108MHZ 20UQFN
SI4713-B30-GMR
IC TX FM RADIO RPS/RDS 20UQFN
SKY12146-321LF
IC VAR VOLT ATTEN 12QFN
SN171GG-NR
SNAP PROTOBOARD W/NO RADIO
SWLP.2450.12.4.B.02
ANTENNA WI-FI WLAN 2.4GHZ
TD4A
SENSOR RTD LIQUID TEMP 2TERM
TD5A
SENSOR RTD TEMP MINI 3LEAD
相关代理商/技术参数
SI4021-A1-FTR
功能描述:射频发射器 Transmitter EZRadio RoHS:否 制造商:Micrel 类型:ASK Transmitter 封装 / 箱体:SOT-23-6 工作频率:300 MHz to 450 MHz 封装:Reel
SI-40222
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40222
SI-40223
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40223
SI-40227
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40227
SI-40228
制造商:Bel Fuse 功能描述:CONN RJ-45 RCP 32 POS 2.54MM SLDR RA TH 48TERM 4PORT - Trays
SI-40229
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40229
Si4022-A0-FT
功能描述:射频发射器 Transmitters IA4222 RoHS:否 制造商:Micrel 类型:ASK Transmitter 封装 / 箱体:SOT-23-6 工作频率:300 MHz to 450 MHz 封装:Reel
SI4022-A0-FTR
功能描述:射频发射器 Transmitter EZRadio RoHS:否 制造商:Micrel 类型:ASK Transmitter 封装 / 箱体:SOT-23-6 工作频率:300 MHz to 450 MHz 封装:Reel