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REF3430: Samples do not seem to function: zero or wrong output voltage

Part Number: REF3430
Other Parts Discussed in Thread: REF3240, REF3425,

I have a prototype amplifier circuit (a handful of identical boards) which uses REF3240 at a supply voltage of 5V and work fine. Since I would like to reduce the supply voltage to 3.3V, I decided to replace REF3240 by REF3430. I had ordered 5 pieces of the latter as a sample, and another 5 pieced of REF3425. Now, none of the samples seem to work.

I tested some of them as a drop-in replacement on two of the mentioned boards, and the last remaining REF3430 on a breakout board with a supply voltage between 3.3V and 6.3V and a load of 12kOhm. Depending on the part being used, the output voltage may be 0V, 1.4V, 1.8V - but never the specified 2.5V or 3V. In one case, the output voltage even rised from 1.8V to 2.4V when reducing the load to 1kOhm.

An electronics engineer from a neighboring company double checked my results and came to the same conclusion.

Do you have any idea what may have gone wrong here? Are there any recent production issues known?

  • Hi Gunnar,

    If you are not using the force and sense functionality of the REF34, can you make sure that the out_f and out_s are shorted together. Gnd_f and gnd_s are shorted together. the REF34 does require an output capacitor, make sure that there is one connected as specified in the EC table.

    Can you share your schematic?


  • Hi Marcoo,

    thank you for the hint. On the boards, the output capacitor was indeed forgotten - which did not hinder REF3240 from working fine.

    Would REF3430 really break immediately if the capacitor is missing? I have installed it on breadboard with sufficient supply voltage to IN and ENABLE, GND_F to ground and to a 12k resistor, GND_S to the same end of the resistor, OUT_F and OUT_S to the other end of the resistor. In parallel with the resistor, there is a 100n foil capacitor. It does not work there, either.

  • Yes the output capacitor is necessary for functionality between out_f and GND. No need for an input cap but it is recommended to reduce transients. Is the cap on the breadboard from out_f to gnd or from Vin to gnd?

    There was a few major changes from the REF32 to the REF34 that happened.

    1. Performance was significantly improved for the Iq.

    2. REF34 needs a output capacitor in the range specified in the datasheet.

    3. The Vin/En filter requirement is gone. There is no need for C09 R15 if those were added to meet the REF32 datasheet specs.