# Buck converter output voltage

I'm using this MIC23150-4YMT-TR with fixed output voltage.

On the PCB, I tested the output & found that it is 2.6V and not 1.2V. I checked it on 3 PCBs and all show the same result

Schematics:

• You forgot to ask a question. Jan 25, 2023 at 11:18
• What's the input supply voltage and what load do you have on the output or, what load current? Jan 25, 2023 at 11:23
• Newbie - (a) Although we can guess your question, please state it clearly to give everyone a clear "target" for your question. || For starters, please add the following information to your question: (b) photos of your actual built prototype PCB where you are seeing this behaviour; (c) the PCB layout from the EDA software; (d) the relevant BOM especially L5. || (e) Do you have a scope trace of the output voltage (if so, please supply it) or did you measure the 2.6 V using a DMM? || (f) What voltage is on the EN pin during your tests? || (g) Any other results from your troubleshooting so far? Jan 25, 2023 at 11:41

From labelling I assume the input voltage is 3.3V.

The output is sampled with an on-chip divider (Let's called the resistances R1 and R2 – R1 from output, and R2 to ground) and compared to an internal reference voltage (Vref). So the output voltage will be VOUT = Vref × (1 + R1 / R2).

If there's any resistance on the feedback path (i.e. from output to SNS pin) then the final output voltage will be higher because this resistance will be in series with R1. If this path is open then the chip can't see any feedback so it will constantly increase the duty cycle until it hits pre-defined limit of 80% (Nothing is mentioned about open loop protection so it's quite likely to happen). In this case the output voltage can be as high as VOUT = 3.3V × 0.8 = 2.6V.

Make sure the output connects to the SNS pin. It may not be easy to check as the pin doesn't seem to be easy-access.

• This answer sounds entirely plausible and, if the switching node is checked using a scope then D should equal about 80% Jan 25, 2023 at 12:43