• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 185 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLV320ADC6140: Not able to read DC signal

Rohan Kamra
Prodigy 20 points
Part Number: TLV320ADC6140

We have been able to successfully read AC signals using TLV320ADC6140 but we are having trouble reading the DC signal.

We changed the channel register settings from AC coupled to DC coupled. When we read the signal we get a DC signal centered around 0V. Somehow the DC bias/offset is being removed eventhough the settings has been done for DC coupling.

We want to use one out of four channels of TLV320ADC6140 for reading DC voltage. Currently we are using Channel 3 for this purpose.

Register setting pertaining to Channel 3:

Register 0x46 - 0b00110000  (mic Input, Analog Single ended, DC-coupled, Impedence = 2.5kohm)

Register 0x47 - 0b00000000 (Gain - 0dB)

Register 0x48 - 0b11001001 (Digital Volume Control - 0dB)

Register 0x49 - 0b10000000 (Gain Calibration - 0dB)

Register 0x4A - 0b00000000 (No phase calibration)

Are there any other changes which need to be made to read the DC signal?

  • +1
    TI__Mastermind 23050 points

    Hi Rohan,

    The ADC6140 also has a high pass filter that is applied to all channels and is set to 0.00025*fs by default. You will want to change this to the custom HPF filter setting which is configured as all-pass by default.

    Best,

    Zak

  • 0
    Prodigy 20 points

    Hi Zak

    Thank you for the solution. I'm now able to read DC voltages also.

    I would appreciate if you can help with understanding one more thing. I have been testing the ADC with different DC voltage inputs and it seems like the peak to peak voltage of ADC6140 in differential mode is +/- 2.63V.

    Whereas in the datasheet it is given that the Differential voltage range is 2-VRMS full-scale inputs which as per my understanding means that the peak to peak voltage of the ADC should be +/- 2.83V.

    Can you please help me understand this.

  • 0 in reply to Rohan Kamra
    TI__Mastermind 23050 points

    Hi Rohan,

    The typical full scale range of the ADC is 2Vrms differential, but since these devices are intended for audio applications they are not trimmed for DC precision and can have a gain error of up to 1dB, meaning full scale could actually occur at as low as +/-2.52Vpp.

    Best,

    Zak