UCC3818A: Startup Condition

Kuan Wei Chen (Kevin Chen)

Genius 9710 points

Part Number: UCC3818A
Other Parts Discussed in Thread: UCC3817

Dear Team,

Here is Kevin from Delta Taiwan team.

Customer is testing UCC3818A, it seems during startup the DRVOUT pin will have some driving signal.

Do we have more information explain this IC's condition during startup?

Besides, what is OVP/EN(pin10) condition before and after provide power? (internal resistance)

Kevin

over 3 years ago

0 Mike O' over 3 years ago

TI__Guru 70725 points

Hello Kevin,

Could you explain more what the issue is? Do you have waveforms?

Regards,

Mike

0 Mike O' over 3 years ago in reply to Mike O'

TI__Guru 70725 points

Hello Kevin,

I reviewed an application note by John Bottrill for reducing audible noise on the UCC3817/8 devices.

The cause was due to negative input offset voltage of the current amplifier. It can be removed by adding a 4 mV

offset to the current amplifier non-inverting input.

https://e2e.ti.com/support/power-management/f/196/p/935689/3456858#3456858

I believe the issue you are seeing at startup is due to this negative offset on the current amplifier.

If they add the resistor divider of figure 1 and add a 4 mV of offset to the non inverting pin of the amplifier, they should be able to remove this startup issue.

Regards,

Power management

Power management forum

UCC3818A: Startup Condition