I have designed a development board for L6482. I did solder C1, C2, C3, C4, C5, C6, C7, C8 and D1, then supply 24VDC to test the power scheme of L6482 but VCC is still 0V. Should it be 7.5V after supply 24VDC according to my attached schematic?

[huytung1501]

[Peter BENSCH]

Welcome, @huytung1501​, to the community!

Correct, if the 24V are present at VS and can also be measured at VSREG, and all GND connections are also connected, a voltage of 7.5V should be measurable at VCC and VCCREG in your circuit.

Please also try to measure the current that is drawn via 24V.

Regards

/Peter

[huytung1501]

Hi @Peter BENSCH​ 

The current oscillates from 1mA to 5mA differently each time I turn on the bench power supply.

The strange thing is, VREG presents 0.3V although VCCREG/VCC is 0V. 

[huytung1501]

This is the waveform of VCC during start-up

[Peter BENSCH]

I suspect a problem with the layout, possibly also one with the component.

Do you have a chance to use an EVAL6482H-DISC as a known working board for comparison?

[huytung1501]

@Peter BENSCH​

I could order an EVAL6482H-DISC to use for comparison, but I don't think it can solve my problem.

I tried to solder completely a new board, but same problem. My question is, what could prevent VCC from starting up?

[huytung1501]

@Peter BENSCH​ 

I found the problem. It's not the layout nor the component.

RESET pin: If not used, it should be connected to VREG [Datasheet page 17]

This is not correct, at least in my case.

External control signal is required to drive RESET line to high level so that the internal regulators can work properly.

[Peter BENSCH]

Thank you for the feedback and contribution, I had actually overlooked that too.

If the problem is solved, please mark this thread as answered by selecting Select as best, as also explained here. This will help other users find that answer faster.

Regards

/Peter