TI power supply LM62460 help

jiyu7551

TI power supply LM62460 help [Copy link]

We used TI's LM62460QRPHRQ1 chip and encountered a very strange problem, that is, the output voltage is always 1V, not 5V. We replaced it with LM61495QRPHRQ1 and it was the same. We checked the signal and found that the RESET pin was always 0. We carefully checked the welding and it was not a problem. We changed several boards and the chips were the same. We bought LM62460Q5RPHRQ1 and the output was the same, but the output of LM62460Q3RPHRQ1 was 3.3V. We have been stuck with this problem for more than a month. We bought this chip from several stores and it was basically the same. What is the reason?

tagetage

An open-drain RESET output with filtering and

delayed release gives a true indication of system

status.

tagetage

Why did you choose such a small inductor, 0.75uH?

jiyu7551

tagetage published on 2024-8-7 11:27 An open-drain RESET output with filtering and delayed release gives a true indication of system ...

Yes, its RESET is an output, but where is my problem?

jiyu7551

tagetage posted on 2024-8-7 11:34 Why did you choose such a small inductor, 0.75uH.

He suggested 0.75uH, of course, for a 2.2MHZ switching frequency. My circuit has a 400K switching frequency, so he suggested 2.7uH, and I also used 2.7uH.

tagetage

jiyu7551 posted on 2024-8-7 12:36 He suggested 0.75uH, of course it is 2.2MHZ switching frequency, my circuit is 400K switching frequency, he suggested 2.7uH, I also use 2.7uH ...

If you are 2.7uH, why didn't you say it in the original post? Why is the circuit diagram still 0.75uH? This is your imprecision.

tagetage

Let's do some basic checks first, including schematic diagram, PCB, welding, and measurement of voltage at each pin of the chip. Based on your explanation I cannot help you determine where the problem lies.

beyond_笑谈

First, capture the waveforms at the SW point and CBBOT. From these two waveforms, you can verify whether the output voltage is correct.