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ADS8519: Always ADC output value as even number even though input changes rapidly

MOHAMED SIDIQ
Prodigy 120 points
Part Number: ADS8519

Dear All,

I am working with ADS8519 in one of my project.

The ADC ADS8519 is interface with Spartan6 FPGA through SPI Communication.

The issue is whatever Input is given to the ADC , the correspoing data value always an even number

May I know the reason as why it gives always even value.

Following configuration

1. ADS8519 Configured as to Support +/-10V input.
(By giving :
Input to R1in ;
R2in to GND ;
R3in and CAP Short and givern 2.2uf dacap;
REF decap with 2.2uF;).

2. Data output configured as Straight Binary value by pull up this pin SB/BTC#.

3. for your reference i am attaching the schematic.

Experimernt:

1. Short the Input to GND and get the corresponding value as even number always.

2. Given 1V DC volts to the Input and get the corresponding value as even number always.

3. Given 2V DC volts to the Input and get the corresponding value as even number always.

4 Given 5Vpp sine wave with 2Khz frequency to the Input and get the corresponding value as even number always.

5. Given 8Vpp sine wave with 2Khz frequency to the Input and get the corresponding value as even number always.

Please revert me as soon .

Thanks and Regards,
Mohamed Sidiq.H

  • 0
    TI__Mastermind 24970 points

    Hello,

    Could you specify what value is even? Is the voltage reading even, or is the code?

    For example, if input 1V, do you get 2V, 1.2V, or 13108? Is the error of the measurement from the input large (volts) or closer to an LSB (76.3uV)

    I am trying to see if you are missing a bit when reading the output data.

    Could you take a oscilloscope shot of the communications including BUSY, DATA, DATA CLOCK, RC?

    Regards

    Cynthia

  • 0 in reply to Cynthia
    Prodigy 120 points

    Hi Cynthia,

    Actually when i give an input to the ADC i am getting a corresponding input value as output data:

    My Problem is the sampled ADC data always through's an Even Number values.

    For example:

    If i give an input of 5Vpp sin wave with 2khz frequency i am getting an same 5Vpp of sin wave data  from the ADC when i am plotting on MATLAB.

    But the data sampled value from the ADC is always even number values. Even though i am giving various voltage values like 1v ,2v or 3v of sine and ramp signals.

    If you want any clarification further please let me know.

    Thanks and Regards,

    Mohamed Sidiq.H

  • 0 in reply to MOHAMED SIDIQ
    TI__Mastermind 24970 points

    It sounds like you are missing the last bit,

    Could you specify what value is even? the output code directly from the ADC?

    It will help if you would you take a oscilloscope shot of the communications including BUSY, DATA, DATA CLOCK, RC?

    With the oscilloscope shots, they can be compared with the timing diagram t make sure that communications is correct.

    regards

    Cynthia