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REF3120: output voltage low

Part Number: REF3120
Other Parts Discussed in Thread: TMS320F28335, REF3020, REF3320

Hi, My customer is using REF3120 as the voltage reference of TMS320F28335. The final product is a solar inverter.

They observed around 1.99V instead of 2.048V for about 7-8 times. After they changed another one, the problem is fixed.

The problem is observed after the inverter is returned from the customer due to quality issue.

1. Are there anything improper of the schematic design of REF3120?

2. Are there any upgrade device of REF3120 recommended?

The schematic is as below:

5V source is from 12V through a buck as below:

  • Hi Howard,

    1. Is the +5V at input of REF3120 free from ripple? Think about using an RC-filter at input of REF3120, maybe 4R7 + 2µ2.

    2. Think also about inserting a resistance (about 4R7) between output of REF3120 and REF-input of microcontroller. 

    3. Think about using the REF3020 instead the REF3120.

    Kai

  • Hi Howard,

    1. I don't see anything improper with the schematic design, but i noticed a very large output capacitance (10uF) that may not be necessary. Generally the input capacitance should be larger to help reduce noise from the +5V supply. Kai mentions a RC filter at the input which can also reduce ripple.

    2. The REF3020 or the REF3320 may be an alternative to look at it.

    Overall, I do not think this is a device issue. If the quick fix is to replace the device, then the schematic design should be okay. The problem is only observed when the inverter is returned, which leads me to believe that the device could be damaged in their customer hands. I would talk to your local TI CQE engineer.