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AD8313 evaluation board

Hi

I am using AD8313 evaluation board having (AD8313 and OPAMP AD8009)

http://www.analog.com/media/en/technical-documentation/data-sheets/AD8313.pdf 

My questions are:

1.  The frequency range for AD8313 is 0.1 GHz to 2.5 GHz and AD8009 1 GHZ as per datasheet.

Then how the Evaluation board will run more than 1 GHz frequency?

2. I have given two tone input signal at INHI, VPS2=+5V, VPS1=+4V, GND=VNEG=ground.

I have to operate it into LOG (RSSI) mode so I did not make any changes on the evaluation board, because I believe it is configured  by AD in this mode.

There is confusion regarding switch position, The given link have image of board

https://media.digikey.com/Photos/Analog%20Devices%20Photos/MFG_AD8313-EVALZ.jpg 

Which is position A and B (Near VNEG is it A or B) ?

3. For two tone test signal configuration given in 2  is used, and I have tested the voltage across R5 which is summarized as follows:

I/P power (dBm)      Voltage (V)

-65                                 0.69

-50                                 0.80

-35                                 0.95

-15                                 1.42

-10                                 1.52

-5                                   1.62

Is the above range is right or wrong?

I have to take this output and give to a DAC but the DAC i/p voltage is 512 mv peak to peak.

To interface with DAC I require conditioning circuit so that voltage vary between 0 to 512 mV.

If you have idea of conditioning circuit then please let me know.

Thanks a lot..

Girish

  • 1. AD8009 is on the output of the device. AD8313 provides an output voltage (dc if the input level is fixed) that is proportional to the size of the input signal. So AD8009 is not seeing a 2.5 GHz signal.

    2. According to the schematic, the switch should be in position A which grounds PWDN and enables the part. You are getting an output signal from the part so assume that the switch is in the right position.

    3. Yes and no. To get the board to work correctly, I think that you need to put a negative supply on VPS2. When AD8009 is operated on a single supply its output voltage is only rated to swing down to 1.1 V. So your low end data is non linear because of AD8009.

    4. You can scale down your output voltage by putting a resistor divider on R5 and R6.  If your output is not changing fast, I think that it's safe the connect the resistor divider directly to the ADC. Keep the resistors on the small side though.

  • Dear Enash

    Thanks a lot.

    I have some more queries.

    1. Understood

    2. Kindly elaborate the positions A and B on board near VNEG or opposite.

    3. After putting negative supply on VPS2 can I reduce the output near 0.5 V or less?

    4. I am using LTE signal at 1.9 GHz center frequency and bandwidth of 5 MHz

    Should I connect directly to ADC whose i/p voltage is 512 mv peak to peak range?

  • 2. From the eval board description table "

    SW1

    Device Enable. When in Position A, the PWDN pin is connected to ground and the AD8313 is in normal operating mode. In Position B, the PWDN pin is connected to an SMA connector labeled ENBL. A signal can be applied to this connector.

    SW1 =

     3. If you put a negative output on the AD8009,  then it's output can go all the way to ground. In practice it will go down to the minimum output level of AD8313 which is around0.5V

    4. That depends, your max voltage from the detector circuit needs to be less than the max input voltage of the ADC which I assume is 0 V to 512mV.  If the max voltage from the detector is higher than this, than you need to scale down the detector voltage.

  • Thanks

    2.  I agree with 2 but the A and B is not mentioned on the board.

  • Ok but if you are getting a response at the output, then the switch is in the right position. Don't worry about it.

  • Hi

    I am facing problem the output voltage range varies form 512 mV to 1000mV.

    when I am changing the pot. connected near to AD8009 no impact seen at the output.

    I want to use AD 8009 as a clamper with the voltage scaled down to 0 to 512 mV.

    Kindly suggest if any changes on the board required or I miss something.