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AFE5808A power consumption as a function of input amplitude?

Other Parts Discussed in Thread: AFE5808A

Hi,

I've developed a test circuit for AFE5808A before accomplishing final application to do some measurements and tests.
Lately I've discovered something that makes me confused. One time I observed, that AFE5808A is heating so much. It had never happened before. Normally I do my measurements just for 1 channel but that time the signal was connected to all inputs of AFE. The problem is, that the power consumption grows rapidly along with amplitude of analog input signal.
 IC is heating much for high input amplitude and it cools down in a moment after disconnecting input signals. It behaves the same with only one channel working, but power consumption doesn't grow significantly.
Unfortunately I don't have posibility to measure temperature of IC's package precisely.

Below I present some measurements results of power supply  current of the test board (simple custom board, with AFE and T/R Switch onboard only).

Conditions:

Input signal: sine wave, sampling clock 20 MHz, default register configuration, unless otherwise noted.

Results:

COMPLETE_PDN : supply current - 40 mA (I assume it is consumtion of all other parts on the test board)
VCA_PDN: 230 mA
PDN_ADC: 350 mA

Input signal connected to 1 channel only
----------------------------------------
Input amplitude | supply current
50 mVpp   | 450 mA
100 mVpp | 460 mA
300 mVpp | 490 mA
500 mVpp | 500 mA

Input signal connected to 6 of 8 channels
-----------------------------------------
Input amplitude | supply current
50 mVpp   | 470 mA
100 mVpp | 500 mA
300 mVpp | 620 mA
500 mVpp | 750 mA

I did some other observations:
- changing Vcntl (changing TGC gain) doesn't make significant difference (20 mA max difference from VNTCL=0V to 1.5V)
- changing active termination resistance value or input clamp voltage (to 1.5 Vpp) through configuration register makes no difference.

Finally, my questions:
Is it normal behavior of AFE5808A? Maybe AFE is intended to handle input signals with low duty cycles
(such as 1% suggested in electrical characteristics section of datasheet)?