TPS51623: VCORE Schematic confirmation

Hi,

would you please describe the issue. is system not booting up or shuting down during steady-state?

Thnaks.

Regards,

Rama.

Hi Rama,

It's shut down during boot up as the waveform below, the VNN drop while system booting up.

Hi Chung,

Thanks for waveforms.

From the waveforms, VNN  rail is booting-up properly. it is shuting down during VDDQ rail bootup. To confirm rails coupling noise between VDDQ and VNN,please check following point.

1. Without turn-on VDDQ rail,  check VNN rail shuting down or not?. you can also add some load on VNN rail.

Regards,

Rama.

Hi Rama,

Here is the test result after testing turn-on without VDDQ:

1.The power rail can turn on but sometimes still failed.

2.If the power turns on, the PMW of power rail is very unstable as picture below

3.Add load on this unstable VNN, sometimes it shutdown when load more then 4A. 

Hi,

Thanks for update.

would you please provide all rails inductor DCR values. From schematic, VNN rail inductor DCR vaule is 42 mohm. please confirm.

Regards,

Rama.

Hi Rama,

I had asked customer to provide all rails inductor DCR values. I will update it soon.

Sorry I can't get the datasheet, so may I ask what is the connection between this issue and DCR?  And what's worng about the 42mohm DCR of VNN?

Thank you.

Hi Chung,

Yes. Inductor DCR value will decide the overcurrent limit. In schematic, the over current protection(OCP) pin has 150k resistor, so OCP threshold value is 45mV(min).

For example, if indutor DCR=42mohm, the OCP has limit for ~3A (depens on inductor current ripple)

Thanks.

Regards,

Rama.

Hi Rama,

Update the inductor spec

VCORE & VNN:

VNN_VCORE_MHCC&MHCI-Series.pdf

VGG:

VGG_HPPC Series.pdf