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AD9148 Configuration

Product Number: AD9148

Hello,
I am having a lot of trouble using the AD9148.
I set the AD9148 with a full scale of 20 mA
I try to generate a current between 0 and 20 mA on the 4 outputs of the AD9148, but I never manage to reach the value of the full scale, the value reached is 18 mA, the DAC is used with a circuit similar to the one described in page 62 of the datassent figure 78.
the other problem I encounter is when I try to generate a current of 20 mA on IoutP, I have only 16 mA on IoutP and 2mA on IoutN, whereas I am supposed to obtain a current close to 0 mA on the IoutN output.
What is the possible cause of this dysfunction ?
the other point which poses problem is the configuration of the registers, indeed when I try to add an offset current by setting the registers 2C, 2D, 2E and 2F, there is no change whatever the value written in these registers. I meet the same problem with the registers 0x50 and 0x51.

I use the DAC in the following configuration:
Afull scale = 20 mA
Data format : unsigned binary format, single port .
Is there a particular configuration for setting the registers?

Thank you in advance for your help, I do not understand the cause of these problems


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  • Hi  ,

    Can you provide a capture of your waveforms when you set the AD9148 to its default values? The default settings are full-scale = 20mA, two's complement format (set Register 0x03 [7] to 0b0), and use dual-port mode (set Register 0x03 [5] to 0b1). Also, are you using the AD9148 Evaluation Board (AD9148-EBZ)? If not, can you provide a copy of your schematic? At a full-scale current of 20mA, the output peak-to-peak voltage should be around 1V.

    Regards,

    Marco

  • Hi Marco, 

    Thank you for your Answer, 

    I don't use the AD9148 Evaluation Board, i use the AD9148 with exactly the same schematic as described in figure 78 p60 of the datasheet.

    I use the DAC  in single  port mode, I'dont use DATA PORT B.

    The problem is the presence of a current of 2 mA on the output IoutN when i send DATA equal to 0xFFFF ( input DATA format is unsigned), i'am supposed to obtain a current equal to the full scale on output IoutP and 0 on output IoutN.

    Regards,

    Data converter team 

Reply
  • Hi Marco, 

    Thank you for your Answer, 

    I don't use the AD9148 Evaluation Board, i use the AD9148 with exactly the same schematic as described in figure 78 p60 of the datasheet.

    I use the DAC  in single  port mode, I'dont use DATA PORT B.

    The problem is the presence of a current of 2 mA on the output IoutN when i send DATA equal to 0xFFFF ( input DATA format is unsigned), i'am supposed to obtain a current equal to the full scale on output IoutP and 0 on output IoutN.

    Regards,

    Data converter team 

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