TPS54429: About Bootstrap Capacitor

Tsukui Yusuke

Guru 21930 points

Part Number: TPS54429

Hi,

Could you tell me about Bootstrap cap?
When considering DC bias characteristics, please tell us the recommended capacitance of Cboot.
Customer is forced to change their Cap under the influence of Cap's EOL.

Could you tell me the minimum capacitance and rated voltage required for Cboot.

Best Regards,
Yusuke

over 5 years ago

0 Iven Su over 5 years ago

TI__Expert 8245 points

Hi,

The minimum capacitance and rated voltage required for Cboot I recommend are 0.1uF and 16V, thanks.

0 Tsukui Yusuke over 5 years ago in reply to Iven Su

Guru 21930 points

Su-san,

Thank you for your support.
Let me ask you one more thing.

DC bias characteristics will lower the capacitance.
〉The minimum capacitance and rated voltage required for Cboot I recommend are 0.1uF and 16V, thanks.

I understood that it was OK if it is a 0.1V cap of 16V product.

Is my understanding correct?

If it is correct understanding,

Please tell me the Cboot capacitance (0.0x uF) you are assuming.

Customer is forced to use Cap, which has poor DC bias characteristics.
(It drops to 0.05uF at 5.5V)

Could you give me your advice?

Best Regards,
Yusuke

0 Iven Su over 5 years ago in reply to Tsukui Yusuke

TI__Expert 8245 points

Hi,

The Cboot capacitance should not drop too much, see below:

If your customer use a 0.05uF cap, it might be OK but we cannot guarantee the converter performance on some special conditions, like low drop-out which need Cboot to keep highside switch on. Thanks.

0 Tsukui Yusuke over 5 years ago in reply to Iven Su

Guru 21930 points

Su-san,

Thank you for your kind support.
Customer is considering the following based on your advice.

GRM155R6YA105KE11（1uF/35V/X5R）
(0.51uF@5.5V)

Is it a problem that the capacitance is large?
Could you give me your advice?

Best Regards,
Yusuke

0 Tsukui Yusuke over 5 years ago in reply to Tsukui Yusuke

Guru 21930 points

Su-san,

Is any update?

The customer is considering GRM155R6YA105KE11.
Please advise about availability of GRM155R6YA105KE11.

I look forward to your reply.

Best Regards,

Yusuke

0 Iven Su over 5 years ago in reply to Tsukui Yusuke

TI__Expert 8245 points

Hi,

Using a 0.5uF/5.5V cap should be OK on normal working conditions. Thanks.

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TPS54429: About Bootstrap Capacitor