TPS65917-Q1: Why does 65917 need two input voltage?

Sherry Liang

Part Number: TPS65917-Q1
Other Parts Discussed in Thread: TDA2, TPS43351-Q1

Dear team,

Below is the user guide for TDA2 Eco power supply. Can I change the dual channel buck TPS43351-Q1 to single channel buck/Vout=5V? That means PMIC's input voltage only has one 5V. I don't understand why 65917 needs two input voltage(3.3V, 5V). Can I only use single channel buck/5V to power the 65917?

Thanks & Best Regards,

Sherry

Thanks & Best Regards,

Sherry

over 3 years ago

0 Nastasha over 3 years ago

TI__Genius 10000 points

Sherry,

For this power solution 2 power supplies are needed. This is because LDO1 operates as a load switch, so it needs 3.3V input. LDO4 operates as an LDO so it needs at lease 3.6V. This is why we recommend supplying the device (except for LDO4) with 3.3V. Then, a different supply is still needed for LDO4.

0 Sherry Liang over 3 years ago in reply to Nastasha

TI__Genius 10255 points

Hi Nastasha,

If we use 3.3V to power LDO1, and then use 5V to power other LDO/SMPS, is it ok?

Thanks & Best Regards,

Sherry

0 Nastasha over 3 years ago in reply to Sherry Liang

TI__Genius 10000 points

Sherry,

Yes, that is also an option. This would lower the efficiency of the PMIC, but still operate correctly.

Thanks,

Nastasha

0 Sherry Liang over 3 years ago in reply to Nastasha

TI__Genius 10255 points

Hi Nastasha,

Thanks for your reply!

The customer will use a second stage DCDC to supply PMIC's LDOs except LDO4. This won't lower the efficiency of the PMIC, right?

Thanks & Best Regards,

Sherry

0 Nastasha over 3 years ago in reply to Sherry Liang

TI__Genius 10000 points

Sherry,

What I mean is that 5V to 1.8V or 1.15V will not be as efficient as 3.3V down to 1.8V or 1.15V. Having a majority of the PMIC on 5V input can increase thermals and decrease overall efficiency. It is something to consider, but it may still be okay in the customer's application.

We have a power estimation tool that can show you the difference of efficiency and thermal performance with different input voltages and output loading. Check it out here if you want to look more into the efficiency of both cases: https://www.ti.com/lit/zip/slvc706

Thanks,

Nastasha

0 Sherry Liang over 3 years ago in reply to Nastasha

TI__Genius 10255 points

HI Nastasha,

Thanks for your help!

Best Regards,

Sherry

0 Mahmoud Harmouch over 3 years ago in reply to Sherry Liang

TI__Mastermind 24740 points

Hello Sherry,

I believe the thread is resolved. Please let me know for further question.

Regards, Mahmoud

Power management

Power management forum

TPS65917-Q1: Why does 65917 need two input voltage?