LM5170: Dual phase buck controller LM5170, only use phase-1 for single phase buck circuit?

Aska Lee

Part Number: LM5170
Other Parts Discussed in Thread: LM5145

Question 1) : Do LM5170 only supply single phase buck circuit? Is there anything we should be careful?

My means is we only use phase-1 of LM5170. The phase-2 of power train components are empty.

Reason: For IC selection, we know single phase buck IC is LM5145. If LM5170 is ok, we may save developed time.

Question 2) : We try the simulation tool of LM5170 in TI web side to verify single phase, but both TINA tool and Pspice tool are fail. Could you please provide it if LM5170 is ok for single phase buck circuit?

Thanks

Aska

over 5 years ago

0 Youhao Xi over 5 years ago

TI__Guru* 78270 points

Hi Aska,

Thank you for reaching out. Yes the LM5170 can do single phase buck with CH-2 not used. You should ground all these CH-2 related pins except for COMP2, LO2 and HO2, which I would recommend to terminate each with a 10k resistor to GND.

You should be able to simulate single phase. Can you send us your TINA model so we can take a look?

Thanks,

Youhao Xi, Applications Engineering

0 Aska Lee over 5 years ago in reply to Youhao Xi

Intellectual 610 points

Hi Youhao,

Thanks for your answer.

May I have your e-mail? I can send the TINA model to you any another mail.

Thanks.

0 Youhao Xi over 5 years ago in reply to Aska Lee

TI__Guru* 78270 points

Hi Aska,

Can you just post your TINA model in e2e here? You can attached a file to your post.

Thanks,

Youhao

0 Aska Lee over 5 years ago in reply to Youhao Xi

Intellectual 610 points

Hi Youhao:

Thanks for your help.

Attached is the dual phase model of LM5170.

Aska

snvmb67_LM5170 - 2phase_CV feedback.TSC

0 Youhao Xi over 5 years ago in reply to Aska Lee

TI__Guru* 78270 points

Thanks. Please allow me sometime to debug the model. Will get back to you by next Wed.

0 Aska Lee over 5 years ago in reply to Youhao Xi

Intellectual 610 points

Hi Youhao:

Sure, wait for your good news.

BTW, I fixed the bug of LM5170 model. It can support with dual phase, but still fail in single phase.

Please use new upload file. One is dual phase, another is single phase.

Thanks.3058.snvmb67_LM5170 - 2phase_CV feedback.TSC snvmb67_LM5170 - 1phase_CV feedback.TSC

0 Youhao Xi over 5 years ago in reply to Aska Lee

TI__Guru* 78270 points

I checked your single phase circuit and found the main issue is that you did not have the Fault Detection disabled. Please refer to the datasheet. You need to place a 10k resistor across SYNCOUT and GND to disable the Fault Detection, otherwise the IC remains in shutdown.

In addition,

(1) R9 should be about 64K according to datasheet Rramp selection

(2) You should reduce the IC SS pin capacitor to say 100pF to reduce the IC inner current loop soft start time, but increase R28 to maybe 5k to increase the voltage loop soft start time, in order to allow the voltage loop as the master control of soft start, in this way you can avoid inrush current and output overshoot at startup.

Sorry I am currently on a biz trip and I did not have time to check your dual phase model. If you have similar problem there, please make the same changes as mentioned above

Thanks,

Youhao

0 Aska Lee over 5 years ago in reply to Youhao Xi

Intellectual 610 points

Hi Youhao:

You are right. The key is nFault function.

Now the single phase of LM5170 model is workable.

Double check one thing - If we need 1 phase of LM5170, the Fault detection shall be disabled. It means there is no MOSFET failure detection for drain-to-source shorted.

Am I right? Or it can be reserved by which circuit.

Thanks for your help.

Power management

Power management forum

LM5170: Dual phase buck controller LM5170, only use phase-1 for single phase buck circuit?