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TLC7226: TLC7226 voltage output error

Rohit Baranwal
Expert 1025 points
Part Number: TLC7226
Other Parts Discussed in Thread: LM431

Hi, I am trying to use a TLC7226 DAC for generating a precise 0-10V reference that can be controlled through a microprocessor. These are the settings of the DAC:

Vdd: 15V. (Wall adapter with 15V output, 1.5A max)

Vss: GND

AGND: GND

DGND: GND

Ref: +10V (LM431), measured using two multimeters

I have kept more than 4V margin needed between the Vdd and Ref voltages as per the datasheet. However, I am observing a drift in the DAC output. Here are the outputs:

Digital input 0: 0.001V (measured using two multimeters). Expected output is 0V

Digital input 170: 6.2V (measured using two multimeters). Expected output is 6.67V

Digital input 255: 9.45V (measured using two multimeters). Expected output is 10V.

The digital inputs are 0-5V signals, coming from the microprocessor. I am looking at the digital bits on an oscilloscope cope to verify that the digital input to DAC corresponds to what I am commanding.

Can someone help me understand the possible cause? On a side note, I am using the following demo board for the DAC for my experiments:

https://www.industrologic.com/updac8man.htm

  • 0
    TI__Genius 14220 points
    Hi Rohit,

    Thank you for your query. Every DAC will have non-idealities defined as zero-code error, offset error, gain error, full-scale error etc. If you are comparing the measured results against the ideal expected values, you will always face these errors whose maximum defined in the datasheet. These errors can be calibrated at a system level if absolute accuracy is required.

    However, if you are suspecting that the errors are larger than the values specified in the datasheet, we need to look deeper into it to find out what might be the root cause. Depending on the system design and layout, there might be additional error due to parasitic effects.

    Regards,
    Uttam Sahu
    Applications Engineer, Precision DACs
  • 0 in reply to Uttam Sahu
    Expert 1025 points

    Hi Uttam, thanks for the reply. The datasheet specifies +/-2 LSB error for full scale error. I rechecked and actually, I was getting 9.94, not 9.4. So yeah, the error is within margin and it is acceptable.