Tps51116 vout drop when havy load?

You may possibly have the current limit st too low. Try increasing it.

Hi John

The TPS51116 seems use RDson to sense current, so, if i want to have more i need change more low rdson MOS?
Bogey

There are two kinds of current sense, RDSon and resistor sensing. For RDSon sensing you can adjust the current limit with the resistor connected to CS pin. See the datasheet page 17, equations 4 and 5.

Hi John
we have try to change R244(Rtrip) from 15K to 35.7K, but vout still drop from 1.2V to 1.05V . is there have other suggestion?
May we having LM51116 reference design for skylake?
Bogey

Changing Rtrip should increase the current limit. Does the voltage drop dc level or only a load transient? I don't directly support TPS51116, so I do not know what reference designs may be available other than what is posted on the web page. Let me see if I can find someone to help.

Hi Bogey,

Can you check the voltage of VDDQSET pin (the voltage across R220) to see if it is 0.75V?

Thanks

Qian

Hi Qian

 the voltage of VDDQSET pin (the voltage across R220)measure 0.75V in light load,

 and heavy load measure about 0.6V.

we also have try to adj VDDQ from 1.2V to 1.35V voltage to measure waveform for reference.

Hi Bogey,

I tested the EVM at below condition, and I did not see the problem at load conditions. The Vout is 1.2V and VDDQSET is 0.75V at either no load or load condition.

-DCAP mode (connnect COMP to 5V)

-VDDQ=1.2V (47kohm and 75kohm resistor divider)

-5Vin

Can you replace TPS51116 controller to see if the problem is still there?

If the problem persists, can you send me the layout design file (not screen shot) to Q-CHEN AT TI.COM, so I can check if there is layout issue.

Thanks

Qian