LMP90080

Rolf Deck

Hi,
I `m testing an ADC LMP90080-Q1
The following Problems have been occurred:
If I activate the Fixed Gain Amplifier (CHx_Config Register, Gain Select 0x4) the Gain of the System should be 16x.
But I can Measure just a gain from aprox. 2x.
The same happens if I chose a higher gain.
The measured Values with just the PGA (Gain 1, 2, 4, 8) are ok.
I changed the ADC, to exclude a Hardware Error, the results are the same.

Have you any Idea what to do ?

over 12 years ago

0 Michael Stout over 12 years ago

TI__Genius 16890 points

Hi,

Could you tell me what VIN pins you are using and the voltages on them? Also what are the voltages on the VREFP and VREFN pins?

Thanks,

Mike

0 Rolf Deck over 12 years ago in reply to Michael Stout

Prodigy 30 points

Hello Mike

Thanks for the fast reply

I use Vin0 (Input Voltage +160mV ) and Vin1(GND) ,

VREFN1 = GND

VREFP1 = 5V

Chan Input Control Register 0x01

Chan SCAN MODE REG. 0x40

Best regards Rolf

0 Michael Stout over 12 years ago in reply to Rolf Deck

TI__Genius 16890 points

Hi Rolf,

It may be caused by the input voltage not being in the input range. For a gain of 16 and above the input voltages must be above GND + 0.4V. See page 7 of the datasheet. Try shifting the input voltage up on both pins and that may solve the problem.

Mike

0 Rolf Deck over 12 years ago in reply to Michael Stout

Prodigy 30 points

Hi Mike

It works, Thanks for the Help

Rolf

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LMP90080