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Original question:

REF5025: REF5025

REF50: Only 1.9V output voltage from REF5025AID

Mattias Andersson
Prodigy 10 points
Part Number: REF50
Other Parts Discussed in Thread: ADS8885

Tool/software:

I use REF5025AID in a new design with 3.0V supply voltage, it outputs 1.9V at pin 6 (and VOUT voltage change when loaded with 2.2k).

I have replaced with new circuit, still same problem.

I connected one ic directly to 3.0V supply voltage only, see picture. Still 1.9V-2.1V output, and unregulated as it increases with input voltage and never stable 2.5V as I am expected.

What is happening here?, according to datasheet operating voltage Vin can be as low as Vref + 0.2V ( I use 3.0V).

  • 0
    TI__Expert 3120 points

    Hi,

    The datasheet states in section 8.4.1 that there must be a 1µF to 50µF capacitor connected from VOUT to GND, and recommends a 1µF to 10µF bypass capacitor from VIN to GND.

    Additionally, the dropout voltage spec of VOUT + 0.2V is only valid for unloaded conditions. Please refer to Figure 6-6 in the datasheet which shows the dropout voltage vs load current at various temperatures.

    Adding the bypass and load capacitors and ensuring that the dropout voltage requirements are met should provide the expected performance for the device.

    -Henry

  • 0 in reply to Henry Naguski
    Prodigy 10 points

    Hi Henry, thank you very much. We had missed the capacitor on the output.

    With 2.2uF directly on pin 6 to ground all is good, 2.499V !

    Please advice your colleagues at ADC department to revise data sheet for ADS8885, page 30 Figure 67 (Schematic of a reference voltage circuit) has a 1kOhm in series with a 1uF, that did not work in our design.

    Thanks again!