AD8310 Evaluation Board behavior

Hi all,

I am using the AD8310 Eval board with no changes (as yet).

Basic testing used input of sine wave with frequencies 5, 50 and 100 MHz and amplitude ranging from 1mV to 1V p-p.

Driving AD8310 single-ended.

Measuring output with DVM and linearity seems OK. Intercept and slope are very consistent across these 3 frequencies.

However, 2 things are bothering me.

1. With no input at either INHI or INLO the residual noise (maximum level) at output is around 720mV. I can reduce this to about 540mV by shorting INHI to INLO.

2. For input sine 5MHz and 1Vpp I see that output is a waveform with fundamental 10MHz (sort of expected) but p-p of 600mV !! Is this large value expected? Of course, as input frequency increases the pp amplitude of the output decreases, but still much more than I would have thought. Also more than in Ltspice.

 I would appreciate any help on this.

David

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  • +1
    •  Analog Employees 
    on May 24, 2021 7:49 PM

    Hello David,

    1. 540mV is somewhat higher than depicted in datasheet Figure 3 for no signal, but understand this graph shows typical response, and actual response is subject to production variation. You might try simply terminating the eval board RF input with 50 ohm SMA termination, as opposed to shorting INHI to INLO. 

    2. Yes, this is normal for an unmodified eval board. Datasheet section "OUTPUT FILTERING" on page 18 discusses how the widest output video filter bandwidth should always be less than the lowest RF input frequency. The factory eval board has provision to correct this, C3 on the BFIN pin. 

    Hope this helps.  -Bruce H. 

  • Hi Bruce,

    Thanks for the two answers.

    1. Terminating helped a bit.

    2. Understood.

    David

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