TPS65218: DCDC4 Schottky diode recommendation

Zhou Fang67

Part Number: TPS65218

Hi Expert,

I met the same DCDC4 start-up issue, as threads recommended, the problem can be resolved by adding schottky diode on L4A pin to GND.

New sample of TPS65218D0 is still on the way, we need to implement work around for test purpose temporarily.

We have 2 questions regarding this problem:

1. May I know the forwarding current required for schottky diode for start up?

2. What mechanism for inrush current is triggered for TPS65218B1 to lead this problem?

Thanks.

Zhou

over 7 years ago

0 Gordon Varney over 7 years ago

TI__Genius 9380 points

Zhou,
I have forwarded your question to our product specialist for this part. He should respond soon.

0 Brian Berner over 7 years ago

TI__Mastermind 30280 points

How long until your TPS65218D0 samples arrive?

It does not seem like a good idea to implement a workaround simply for test purposes when the workaround is not required for -D0 silicon.

Also, it appears this question is very similar to one that was asked a couple hours earlier: e2e.ti.com/.../692751

Can you confirm if these questions are related?

0 Brian Berner over 7 years ago in reply to Brian Berner

TI__Mastermind 30280 points

Zhou,

I answer this question in more detail in the other e2e question directly from customer:
e2e.ti.com/.../2553931

The mechanism is that soft-start is disabled when VIN is high, or when DCDC4 starts up in Buck only mode. Since DCDC4 is a Buck-Boost, there are essentially 3 modes of operation: Buck-only, Boost-only, and Buck-Boost combined.

As long as VIN < 3.4V during start-up, then DCDC4 will start-up correctly without additional components. This should be enough info to test and not require a Schottky diode. Then your TPS65218D0 samples will arrive and no more workaround will be required.

0 Zhou Fang67 over 7 years ago in reply to Brian Berner

TI__Expert 4250 points

Brian,

Thanks for your information. The workaround is not 100% effective for cases.
We will verify with new samples.

Thanks.
Zhou

Power management

Power management forum

TPS65218: DCDC4 Schottky diode recommendation