LMR38020: Is there a controller(Using external FETS) with Vin 48V and similar functionality as LMR38020?

Prem Ankitkumar Shah

Part Number: LMR38020
Other Parts Discussed in Thread: LM5145, LM5148

Tool/software:

Hi,

I’m planning to use a PWM controller in My Buck converter application and use External FETS. Below are the desired specifications :

Vin : 48-52V
Vout : 12-36V
Pout : 1W- 24W
Fsw: 100k -1MHZ

I'm looking for a controller (Using external FETS) which has an external pin by which I can set the threshold to enter into SKIP/PFM mode at light load automatically. Does TI has a controller with these options?

I was looking at LMR38020 but it is not optimized for my application.

Thanks!

2 months ago

0 Richard Fu22 2 months ago

TI__Mastermind 25200 points

Hi Prem,

As far as I'm aware, we do not have a device that has a pin that can be used to set the minimum peak current limit. Usually a value is selected during the part definition. If you are looking for controllers in general you may find one here through these filters:

https://www.ti.com/power-management/acdc-dcdc-controllers/products.html#1129=Buck&238max=30%3B700&

Thanks,

Richard

0 Prem Ankitkumar Shah 2 months ago in reply to Richard Fu22

Prodigy 140 points

Hi Richard,
Thank You for your prompt response.

Specifically, I'm looking for a controller which will allow the converter to enter into PFM/SKIP mode around 100mA load for my application.
I did find LM5145 which does diode emulation, however I'm not sure if in diode emulation LM5145 drops switching frequency at light load to improve efficiency. If it does, it would be great to have Iload v/s frequency plot in diode emulation to optimize the design.

I Appreactite your help.

Best,
Prem

0 Richard Fu22 2 months ago in reply to Prem Ankitkumar Shah

TI__Mastermind 25200 points

Hi Prem,

Usually with PFM/SKIP mode, the switching frequency will drop at light load since it will issue pulses until the output voltage is higher than the regulated target voltage by a certain threshold, and then it will stop switching. I'm not sure if this plot is characterized, I will loop in the apps engineer for it.

Thanks,

Richard

0 Prem Ankitkumar Shah 2 months ago in reply to Richard Fu22

Prodigy 140 points

Thank You Richard, That would be very helpful.

Best,
Prem.

0 Timothy Hegarty 2 months ago in reply to Prem Ankitkumar Shah

TI__Guru 62777 points

Hi Prem,

The LM5148 80V peak current-mode controller is your best option for high light-load efficiency. The peak current in PFM is the one-fifth of current limit setpoint (but not adjustable). For example, if the current limit setpoint is set at 125% of the rated output current, then the peak current in PFM is 25% of load, meaning Iout is 12.5%.

Regards,

Tim

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LMR38020: Is there a controller(Using external FETS) with Vin 48V and similar functionality as LMR38020?