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MICRF022YM-FS48 参数 Datasheet PDF下载

MICRF022YM-FS48图片预览
型号: MICRF022YM-FS48
PDF下载: 下载PDF文件 查看货源
内容描述: 300-440MHz QwikRadio系列? ASK接收器 [300-440MHz QwikRadio? ASK Receiver]
分类和应用: 商用集成电路光电二极管
文件页数/大小: 17 页 / 373 K
品牌: MICREL [ MICREL SEMICONDUCTOR ]
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Micrel, Inc.  
MICRF002/RF022  
MICRF002, allowing the device to operate in applications  
the appropriate fLO for a given fTX:  
where  
significant  
transmitter-receiver  
frequency  
fTX  
misalignment may exist. The transmit frequency may vary  
up to ±0.5% over initial tolerance, aging, and temperature.  
In sweep-mode a band approximately 1.5% around the  
nominal transmit frequency is captured. The transmitter  
may drift up to ±0.5% without the need to retune the  
receiver and without impacting system performance.  
(1)  
fLO = fTX ± 0.86  
315  
Frequencies fTX and fLO are in MHz. Note that two values of  
fLO exist for any given fTX, distinguished as “high-side  
mixing” and “low-side mixing”. High-side mixing results in  
an image frequency above the frequency of interest and  
low-side mixing results in a frequency below.  
The swept-LO technique does not affect the IF bandwidth,  
therefore noise performance is not degraded relative to  
fixed-mode. The IF bandwidth is 430kHz whether the  
device is operating in fixed- or sweep-mode. Due to  
limitations imposed by the LO sweeping process, the upper  
limit on data rate in sweep mode is approximately 5.0kbps.  
After choosing one of the two acceptable values of fLO, use  
Equation 2 to compute the reference oscillator frequency fT:  
fLO  
(2)  
fT =  
64.5  
Frequency fT is in MHz. Connect a crystal of frequency fT to  
REFOSC on the MICRF002. Four-decimal-place accuracy  
on the frequency is generally adequate. The following table  
identifies fT for some common transmit frequencies when  
the MICRF002 is operated in fixed mode.  
Similar performance is not currently available with  
crystalbased superheterodyne receivers which can operate  
only with SAW- or crystal-based transmitters. In sweep-  
mode, a range reduction will occur in installations where  
there is a strong interferer in the swept RF band. This is  
because the process indiscriminately includes all signals  
within the sweep range. An MICRF002 may be used in  
place of a superregenerative receiver in most applications.  
Transmit Frequency fTX  
Reference Oscillator  
Frequency fT  
315MHz  
390MHz  
4.8970MHz  
6.0630MHz  
6.4983MHz  
6.7458MHz  
Step 2: Selecting the Reference Oscillator  
All timing and tuning operations on the MICRF002 are  
derived from the internal Colpitts reference oscillator.  
Timing and tuning is controlled through the REFOSC pin in  
one of three ways:  
418MHz  
433.92MHz  
Table 2. Fixed-Mode Recommended Reference Oscillator  
Values for Typical Transmit Frequencies  
(high-side mixing)  
1. Connect a ceramic resonator  
2. Connect a crystal  
3. Drive this pin with an external timing signal  
Selecting REFOSC Frequency fT (Sweep-Mode)  
The specific reference frequency required is related to the  
system transmit frequency and to the operating mode of  
the receiver as set by the SWEN pin.  
Selection of the reference oscillator frequency fT in sweep-  
mode is much simpler than in fixed mode due to the LO  
sweeping process. Also, accuracy requirements of the  
frequency reference component are significantly relaxed.  
Crystal or Ceramic Resonator Selection  
In sweep-mode, fT is given by Equation 3:  
fLO  
Do not use resonators with integral capacitors since  
capacitors are included in the IC, also care should be taken  
to ensure low ESR capacitors are selected. Application Hint  
34 and Application Hint 35 provide additional information  
and recommended sources for crystals and resonators.  
(3)  
fT =  
64.25  
In sweep-mode a reference oscillator with frequency  
accurate to two-decimal-places is generally adequate. A  
crystal may be used and may be necessary in some cases  
if the transmit frequency is particularly imprecise.  
If operating in fixed-mode, a crystal is recommended. In  
sweep-mode either a crystal or ceramic resonator may be  
used. When a crystal of ceramic resonator is used the  
minimum voltage is 300mVPP. If using an externally applied  
signal it should be AC-coupled and limited to the operating  
range of 0.1VPP to 1.5VPP.  
Transmit Frequency fTX  
Reference Oscillator  
Frequency fT  
315MHz  
390MHz  
4.88MHz  
6.05MHz  
6.48MHz  
6.73MHz  
Selecting Reference Oscillator Frequency fT (Fixed-  
Mode)  
418MHz  
As with any superheterodyne receiver, the mixing  
between the internal LO (local oscillator) frequency fLO and  
the incoming transmit frequency fTX ideally must equal the  
IF center frequency. Equation 1 may be used to compute  
433.92MHz  
Table 3. Sweep-Mode Recommended Reference Oscillator  
Values for Typical Transmit Frequencies  
M9999-070808  
July 2008  
8