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AMC3330: Frequency expectations vs. Simulation mismatch

Jaynie Shorb
Prodigy 30 points
Part Number: AMC3330


Hi

I downloaded the TINA Spice sbam456b. 

Filter 1 is what is on the EVM and what was default in the sbam456b circuit. R1=R2=10ohms C=10nf with a cutoff freq of 796kHz

Freq Vin Vout Gain Input Filter Error = (Ideal - measured)/Ideal - 1
1k +/-1V +/-2V 2 Filter1 0%
50k +/-1V +/-1.98V 1.98 Filter1 1%
100k +/- 0.999V +1.91/-1.92V 1.911912 Filter1 4%
150k +/- 0.980V +1.81/-1.82V 1.846939 Filter1 8%
200k +/- 0.999V +/-1.73V 1.731732 Filter1 13%
375k +/- 0.9V +/-1.05V 1.166667 Filter1 42%
1k +/-1V +/-2V 2 No 0%
50k +/- 0.998V +/-1.98V 1.983968 No 1%
100k +/- 0.999V +/-1.93V 1.931932 No 3%
150k +/- 0.999V +/-1.85V 1.851852 No 7%
200k +0.998/-0.997V +/-1.74V 1.745236 No 13%
375k +0.996/-0.997V +/-1.16V 1.164659 No 42%

I'm not expecting any loss of amplitude @vout at 50k, 100, 150k, 200kHz.  I realize the typical BW from the datasheet is 375kHz, but the output graph looks flat for the lower frequencies.

Please explain.

Thanks,

Jaynie

  • +1
    TI__Expert 6750 points

    Hi Jaynie,

    The gain will change slightly much before the typical BW.  Note that Figure 6-9 is in dB, and using the gain values from your simulation: @1k = 2V/V -> 6dB and @100k = 1.932V/V -> 5.7dB, which is only a delta of -0.3dB.  That small of a difference won't really be resolvable from the graph.

    Thanks.