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DDC232: Technical question for DDC232CKZXGT

Takashi Matsumura
Intellectual 775 points
Part Number: DDC232

Hi TI Team,

Thank you for your support.

I have a question about DDC232CKZXGT (A/D converter)

We are debugging our prototype board. But DDC232CKZXGT is unexpected input operation.

We could be misunderstood, or We didn't put important circuit or may put too much.  

So, could you give some advice?


1. When DDC232CKZXGT integrated with Photodiode (without current).

*Which is the data read by ADC 100％FS (0xFFFF) or 0％FS (0x0100?

 

2. Could you provide schematics which Photodiode array connected anode common and cathode common to the parts?

Thank you for your patience.

Kind Regards,

Takashi Matsumura

T4532730

  • +1
    TI__Mastermind 19815 points

    Hi,

    May I ask which customer is this?  If not able to disclose in public, please let me know, i can send you email to ask.

    ---------------------------------------------------------------------

    (1)

    Could customers check whether their VAVDD, DVDD, VREF are correct?

    See if they can reduce the integration time and/or change the range?

    Could they check whether they could read the Test Pattern correctly as shown in datasheet page 11 Configuration Register section?

    The data format is shown in datasheet page 20 "Data Format" and Table 12

    (2)

    Could they check whether they connect the photodiode in the correct orientation as shown in the datasheet figure 3?

    How do they make sure their is no current through the photodiode?  There could be some leakage current and ambient light that excite the photo current?

    ---------------------------

    Thanks

  • +1
    TI__Expert 4640 points

    Hi Takahashi-san,

    To answer your specific question, if I got it right #1, when there is not current coming from the PD, the output would be 0%FS or something close to the code 4096 (0.04% of 0xFFFFF) with a slight error of few hundred codes due to offset.

    On #2. as Chien was saying below, you can look at figure 3. There is only the possibility of common cathode as the current has to flow into the DDC (see arrow direction on that figure). The only way to connect an array with common anode is to actually apply a bias resistor in series with the diode, like it is explained in this app note.

    Regards,

    Edu