LM70660: Layout Questions

Francis Jiang

Expert 4140 points

Part Number: LM70660

Tool/software:

Hi Team,

Customer use LM70660 with below layout questions, could you please help check them? Thanks.

Currently, they connected AGND with PGND, is it correct?
17-pin AGND and 30-pin PGND are connected together inside the IC, so whether there is a need to connect them together in the external circuit? They are connected together on the EVM, could you please help explain the reason here?
Whether this device must uses shunt + amplifier to do current sensing?

BRs,

Francis

9 months ago

+1 Ben C 9 months ago

TI__Guru 56345 points

Hi Francis,

Francis Jiang said:
Currently, they connected AGND with PGND, is it correct?

Yes, that is correct.

Francis Jiang said:
17-pin AGND and 30-pin PGND are connected together inside the IC, so whether there is a need to connect them together in the external circuit? They are connected together on the EVM, could you please help explain the reason here?

No, AGND and PGND are not connected together internally and therefore both AGND and PGND need to be connected externally on the EVM.

Francis Jiang said:
Whether this device must uses shunt + amplifier to do current sensing?

Yes, the device needs to sense the current in order for the current limit circuit to operate.

Ben

0 Francis Jiang 9 months ago in reply to Ben C

TI__Expert 4140 points

Hi Ben,

Thanks for your reply, but customer said that they tested the AGND and PGND, they are short-circuit, whether this is normal? Or the IC is failed? Thanks.

BRs,

Francis

0 Ben C 9 months ago in reply to Francis Jiang

TI__Guru 56345 points

Hi Francis,

Can you tell me how they tested AGND and PGND? I will ask the design engineer to verify if AGND and PGND are connected internally.

Ben

+1 Ben C 9 months ago in reply to Ben C

TI__Guru 56345 points

Hi Francis,

The designer said that AGND and PGND are connected internally

Ben

0 Francis Jiang 9 months ago in reply to Ben C

TI__Expert 4140 points

Hi Ben,

Thanks for your check. Customer measured it by multimeter.

And customer has some further questions about this device, which causes to failed, they will provide the test waveform here later.

BRs,

Francis

0 Ben C 9 months ago in reply to Francis Jiang

TI__Guru 56345 points

Hi Francis,

Please keep me posted.

Ben

0 Ben C 9 months ago in reply to Ben C

TI__Guru 56345 points

Hi Francis,

Are there any updates?

Ben

0 Ben C 9 months ago in reply to Ben C

TI__Guru 56345 points

HI Francis,

I reached out to you via webex chat.

Ben

0 Francis Jiang 9 months ago in reply to Ben C

TI__Expert 4140 points

Hi Ben,

Thanks for reaching out, currently there is no questions here.

BRs,

Francis

0 Yunduo Yang 9 months ago in reply to Francis Jiang

Prodigy 10 points

Our problem is that when the input voltage exceeds 38V, the upper tube will enter the amplification area and be damaged. Figure CH1: lower tube VDS, CH2; VCC voltage; CH3; Cboot voltage. It can be seen that in the normal working waveform, the Cboot voltage always drops, accompanied by the upper tube entering the amplification area, and then the chip is damaged.

It can be seen that before the damage, the lower tube VDS showed multiple waveform voltage drops, and it is suspected that the upper tube entered the amplification area.

0 Ben C 9 months ago in reply to Yunduo Yang

TI__Guru 56345 points

Hi Yunduo,

Do you have a schematic that we can review? The images do not look correct for proper function. Also, please fill in the quickstart calculator.

Ben

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LM70660: Layout Questions