LP2998: About PVIN and AVIN

mayumi.T

Expert 1015 points

Part Number: LP2998

Hello,

My customers are considering using LP 2999 as a QDR termination.
VDDQ = 1.5 V
VTT = 0.75 V

As another power source on the board,
There are 3.3 V, 1.8 V, 1.5 V, 1.2 V, and 1.0 V.

Please tell us which voltage is best to input to AVin and PVin.

Thank you.

over 6 years ago

0 Qian Chen over 6 years ago

TI__Mastermind 24075 points

Hello,

I suggest to use 1V for PVIN to reduce the power loss on LP2998.

AVIN needs to be above 2.2V, so use 3.3V on board for AVIN.

Thanks

Qian

0 mayumi.T over 6 years ago in reply to Qian Chen

Expert 1015 points

Dear Qian

Thank you for your suggestion!
I will tell our customer your answer.

Thank you.

Mayumi

0 Qian Chen over 6 years ago in reply to mayumi.T

TI__Mastermind 24075 points

Hi Mayumi,

Datasheet page 3 says higher voltage on PVIN will increase the maximum continous output current because of output RDSON limitation at voltage close to VTT.

The figure 20 on page 15 shows PVIN is connected to 1.5V in DDR3 application.

To be safe, I think we should suggest customer to connected PVIN pin to 1.5V.

Sorry for the confusion.

Thanks

Qian

0 mayumi.T over 6 years ago in reply to Qian Chen

Expert 1015 points

Dear Qian

Thank you very much.
As you know, the memory they use is QDR rather than DDR 3.
If you have further advice, please let us know.

Thank you.

Mayumi

0 Qian Chen over 6 years ago in reply to Qian Chen

TI__Mastermind 24075 points

Hi Mayumi,

I'm not familar with QDR memory and don't know how much the load current is in customer's application.

The point is if PVIN voltage is close to VTT voltage, the VTT sourcing capability may be limited.

That's why it is suggested to connected PVIN to 1.5V.

Thanks

Qian

0 mayumi.T over 6 years ago in reply to Qian Chen

Expert 1015 points

Dear Qian

We suggest customers to use with PVIN = 1.5V.
Thank you very much.

Mayumi,

Power management

Power management forum

LP2998: About PVIN and AVIN