UCC256404: About pin processing when the HV startup function is not used in UCC256404

Kaji@PAN

Part Number: UCC256404
Other Parts Discussed in Thread: UCC256403

Hello,

UCC256404 has an HVstartup function, but if this function is not used, is it okay to drop the HV pin to GND?
Please let me know if you have any problems such as not working.

Best regards,

over 3 years ago

0 Manikanta Pallantla over 3 years ago

TI__Genius 16155 points

Hi Kaji,

Thanks for reaching out. The UCC256404 has X-cap discharge feature. If the device doesn't see any zero crossings at HV pin, it is going to inject the x-cap discharge current. So, you shouldn't connect HV pin to GND in this device.

If you don't need HV startup and x-cap discharge feature, I would recommend using UCC256403.

Please see the comparison between these devices below.

Regards

Manikanta P

0 Kaji@PAN over 3 years ago in reply to Manikanta Pallantla

Mastermind 7815 points

Thank you for your reply.

However, UCC256403 cannot be obtained due to product procurement.
So it would be helpful if you could tell me what to do with the UCC256404 HV pins when not using them.

Best regards,

0 Manikanta Pallantla over 3 years ago in reply to Kaji@PAN

TI__Genius 16155 points

Hi Kaji,

How are you planning to power up this device if you don't want to use the HV start up?

I am asking because, VCC needs to reach 26V before this controller gives RVCC. And then VCC can be anywhere between recommended voltage.

Regards

Manikanta P

0 Kaji@PAN over 3 years ago in reply to Manikanta Pallantla

Mastermind 7815 points

Thank you for your reply.

My plan is to apply a voltage to the VCC externally at start up time and then power the device with auxiliary windings.
I was planning to apply 13V to VCC, so I didn't expect 26V.
Do you have any good ideas?

Best regards,

+1 Manikanta Pallantla over 3 years ago in reply to Kaji@PAN

TI__Genius 16155 points

Hi Kaji,

There is no way this device would work if you apply 13V at startup. As I mentioned, VCC needs to be raised till 26V.

Regards

Manikanta P

0 Kaji@PAN over 3 years ago in reply to Manikanta Pallantla

Mastermind 7815 points

thank you for your reply.
I will manage to get UCC256403 and consider it on that device.
Best regards,

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UCC256404: About pin processing when the HV startup function is not used in UCC256404