LMR51440: Adjustable Output Buck recommendation

Joseph Wendt

Prodigy 260 points

Part Number: LMR51440
Other Parts Discussed in Thread: LM61440

Tool/software:

Hello,

My customer is looking for a power supply with the following requirements:

Input Voltage: 28V or 36V
Output Voltage: 4V to 27V
Output Current: 50mA to 4A
Application: Motor power supply
Preferences: Integrated solutions where available
Control Method: Voltage controlled via microcontroller, likely using a DAC

Do we have any options with a flexible output voltage that can be controlled by an MCU DAC?

5 months ago

0 Dino Maslic 5 months ago

TI__Expert 5220 points

Hi Joseph,

Do you have any specific switching frequencies would you like to be at for this device?

Thanks,

Dino Maslic

0 Joseph Wendt 5 months ago in reply to Dino Maslic

TI__Prodigy 260 points

No, no switching frequency preferences

0 Dino Maslic 5 months ago in reply to Joseph Wendt

TI__Expert 5220 points

Hey Joseph,

The LM61440 would be a good option. Is a 4A rated device, and can support the adjustable output voltage you are looking for.

Thanks,

Dino Maslic

0 Joseph Wendt 5 months ago in reply to Dino Maslic

TI__Prodigy 260 points

Can the FB pin take in the DAC input from a microcontroller to control the output voltage dynamically depending on MCU input?

0 Dino Maslic 5 months ago in reply to Joseph Wendt

TI__Expert 5220 points

Yes it can, you can do a basic feedback network as shown below:

If RT = RADJ, then changing VADJ has a 1:1 gain on changing VOUT. If RADJ is 2 time bigger than RTOP, then 1V change on VADJ has a 500mV change on VOUT. And if RADJ is half the size of RTOP, then 1V change on VADJ has a 2V change on VOUT.

Thanks,

Dino Maslic

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LMR51440: Adjustable Output Buck recommendation