原标题：ADI ADL5336带可编RMS检测器的IF VGA解决方案

　　ADI公司的ADL5336是带可编RMS检测器的中频(IF)可编增益放大器( VGA),具有dB线性增益控制,工作频率从低频到1GHz,VGA和AGC工作模式,连续增益控制范围48dB,最大增益时的噪音(NF)为6.8dB,1.0V输出时的IMD3大于62dBc,单电源5V工作,主要用在点对多点无线电,仪表和医疗电子.本文介绍了方框图,VGA1和VGA2功能框图, 基本连接电路图以及评估板电路图,材料清单和元件布局图.

　　ADL5336 : Cascadable IF VGAs with Programmable RMS Detectors

　　The ADL5336 consists of a pair of variable gain amplifiers (VGAs) designed for cascaded IF applications. The amplifiers have linear-in-dB gain control and operate from low frequencies to 1 GHz. Their excellent gain conformance over the control range and flatness over frequency are due to Analog Devices, Inc., patented X-AMP® architecture, an innovative technique for implementing high performance variable gain control.

　　Each VGA has 24 dB of gain control range. Their maximum gain can be independently programmable over a 6 dB range via the SPI. The VGAs can be cascaded to provide a total range of 48 dB. When connected to a 50 Ω source through a 1:4 balun, the gain is 6 dB higher. The second VGA has an SPI programmable input switch that selects one of two external inputs.

　　When driven from a 200 Ω source or from a 50 Ω source through a 1:4 balun, the noise figure (NF) for the composite amplifier is 6.8 dB at maximum gain. The output of each VGA can drive 100 Ω loads to 5 V p-p maximum.

　　Each VGA has an independent square law detector for autonomous, automatic gain control (AGC) operation. Each detector setpoint can be programmed independently through the SPI from −24 dBV to −3 dBV in 3 dB steps. When both VGAs are arranged in AGC mode and are programmed to the same setpoint, the composite NF increases to 9 dB when backed off by 18 dB from maximum gain.

　　The ADL5336 operates from a 5 V supply and consumes a typical supply current of 80 mA. When disabled, it consumes 4 mA. It is fabricated in an advanced silicon-germanium BiCMOS process and is available in a 32-lead exposed paddle LFCSP package. Performance is specified over a −40°C to +85°C temperature range.

　　ADL5336主要特性:

　　Pair of VGAs with rms AGC detectors

　　VGA and AGC modes of operation

　　Continuous gain control range: 48 dB

　　Noise figure (NF) = 6.8 dB at maximum gain

　　IMD3 > 62 dBc for 1.0 V p-p composite output

　　Differential input and output

　　Multiplexed inputs for VGA2

　　Programmable detector AGC setpoints

　　Programmable VGA maximum gain

　　Power-down feature

　　Single 5 V supply operation

　　ADL5336应用:

　　Point-to-multipoint radios

　　Instrumentation

　　Medical

　　图1.ADL5336方框图

　　图2. VGA1功能方框图

　　图3. VGA2功能方框图

　　图4.ADL5336基本连接电路图

　　图5.ADL5336评估板电路图

　　评估板材料清单(BOM):