欢迎访问ic37.com |
会员登录 免费注册
发布采购

AD608AR-REEL 参数 Datasheet PDF下载

AD608AR-REEL图片预览
型号: AD608AR-REEL
PDF下载: 下载PDF文件 查看货源
内容描述: 低功率混频器/限制器/ RSSI 3 V接收器IF子系统 [Low Power Mixer/Limiter/RSSI 3 V Receiver IF Subsystem]
分类和应用: 射频微波限制器局域网
文件页数/大小: 16 页 / 326 K
品牌: ADI [ ADI ]
 浏览型号AD608AR-REEL的Datasheet PDF文件第7页浏览型号AD608AR-REEL的Datasheet PDF文件第8页浏览型号AD608AR-REEL的Datasheet PDF文件第9页浏览型号AD608AR-REEL的Datasheet PDF文件第10页浏览型号AD608AR-REEL的Datasheet PDF文件第12页浏览型号AD608AR-REEL的Datasheet PDF文件第13页浏览型号AD608AR-REEL的Datasheet PDF文件第14页浏览型号AD608AR-REEL的Datasheet PDF文件第15页  
AD608  
supply as a reference, but also causes the RSSI output and the  
ADC output to track over power supply variations, reducing  
system errors and component costs.  
RSSI OUTPUT  
The logarithmic amplifier uses a successive-detection architecture.  
Each of the five stages has a full-wave detector; two additional  
high level detectors are driven by attenuators at the input to the  
limiting amplifiers, for a total of seven detector stages. Because  
each detector is a full-wave rectifier, the ripple component in  
the resulting dc is at twice the IF. The AD608 low-pass filter has  
a 2 MHz cutoff frequency, which is one decade below the 21.4 MHz  
ripple that results from a 10.7 MHz IF.  
POWER CONSUMPTION  
The total power supply current of the AD608 is a nominal  
7.3 mA. The power is signal dependent, partly because the RSSI  
output increases (the current is increased by 200 μA at an RSSI  
output of +1.8 V), but mostly due to the IF consumption of the  
band-pass filter when driven to 891 mV, assuming a 4 dB loss  
in this filter and a peak input of +5 dBm to the log-IF amp. In  
addition, the power is temperature dependent because the  
biasing system used in the AD608 is proportional to the  
absolute temperature (PTAT).  
For operation at lower IFs, such as 450 kHz or 455 kHz, the  
AD608 requires an external low-pass filter with a single pole  
located at 90 kHz, a decade below the 900 kHz ripple frequency  
for these IFs. The RSSI range is from the noise level at approx-  
imately −80 dBm to overload at +15 dBm and is specified for  
1 dB accuracy from −75 dBm to +5 dBm. The +15 dBm  
maximum IF input is provided to accommodate band-pass  
filters of lower insertion loss than the nominal 4 dB for  
10.7 MHz ceramic filters.  
TROUBLESHOOTING  
The most common causes of problems with the AD608 are  
incorrect component values for the offset feedback loop, poor  
board layout, and pickup of radio frequency interference (RFI),  
which all cause the AD608 to lose the low end (typically below  
−65 dBm) of its RSSI output and cause the limiter to swing  
randomly. Both poor board layout and incorrect component  
values in the offset feedback loop can cause low level oscillations.  
Pickup of RFI can be caused by improper layout and shielding  
of the circuit.  
DIGITIZING THE RSSI  
In typical cellular radio applications, the RSSI output of the  
AD608 is digitized by an analog-to-digital converter (ADC).  
The RSSI output of the AD608 is proportional to the power  
supply voltage, which not only allows the ADC to use the  
Rev. C | Page 11 of 16