LM5157: Non-isolated buck converters up to 60W

Arijav

Part Number: LM5157
Other Parts Discussed in Thread: LMR33640, LM61460, LMR51440, LMR51450, LM62460, LMQ61460

Tool/software:

Hello,

I am in the process of designing an isolated gate driver with highly flexible gate voltages (Vgs_on from 4V up to +25V, Vgs_off from 0V down to -20V). In my architecture I will first use 2 isolated flyback transformers to generate fixed +/-30V, each side providing up to 60W. I would like on the secondary side to set via one or two (depends on the IC possibilities) non-isolated buck converters the positive and negative gate voltages. Each side should be able to handle up to 60W (slightly less as this is the maximum that the iso-flyback will deliver). Additionally I will have another (or the same, depending on the IC possibilities) buck converter to generate a 5V output for other digital ICs on the secondary side.

I am looking for a cost and footprint effective part to do the job of the non-isolated buck converter/s. Could you recommend me any parts for that matter? It would be important to have a way to somehow be able to regulate the voltage outputs via a microcontroller (DAC or whatever necessary).

Thanks,

Javier

7 months ago

0 Arijav 7 months ago

Prodigy 125 points

Hello again,

after going through the parts I've found 2 which seem attractive getting into some compromise in the upper limit of the output voltage. On one hand the LMR33640 which seems very requires a low part count, on the other hand the LM61460 which is more complex. Would those parts fit?, any further recommendations?

Additionally I see that the LMR33640 ist not recommended for variable output voltage control through an MCU (https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/968108/lmr33640-output-voltage-regulation-through-control-voltage). I've not understood why it is the case and why the LM61460 would be better.

Thanks,

Javier

0 Moritz 7 months ago in reply to Arijav

TI__Genius 15545 points

Hi Arijav,

Thanks for reaching out. I will assign this thread to the responsible team.

Best regards

Moritz

0 Joshua Austria 7 months ago in reply to Moritz

TI__Mastermind 24115 points

Hi Arijav,

Can you please share a diagram of how you are planning to use the buck converters with the power requirements (VIN, VOUT, FSW, IOUT) so I can better assist you?

Thank you,

Joshua Austria

0 Arijav 7 months ago in reply to Joshua Austria

Prodigy 125 points

Hi Joshua,

there will be 2 buck converters directly after 2 isolated flyback. Below you can find the data:

Vin = +30V after the top isolated flyback. -30V after the bottom isolated flyback

Vout = 0 to +25V on the top side and 0 to -25V on the bottom side

FSW = I am open to any switching frequency as long as I get a clean output (not more than 100mVpp) even at low voltages or low load conditions

Iout = I am flexible in the range of 4A to 6A peak current (more is fine if it fits the budget). The load can be lower though

I've seen a setup from your competitor with an LT8640-1 or LT8640S which should work in force continuous mode that can output the 0 to +25V (or 0 to -25V). For several reasons I would prefer to use however TI. Would you have something similar?

Thanks,

Javier

0 Joshua Austria 7 months ago in reply to Arijav

TI__Mastermind 24115 points

Hi Javier,

Here are some options that should fit your conditions. Please feel free to take a look at these and see which fits your needs the best:

LMR51440/LMR51450: 36 VIN, 4/5 A IOUT

LMQ61460, LM62460: 36 VIN, 6 A IOUT

Thank you,

Joshua Austria

0 Arijav 7 months ago in reply to Joshua Austria

Prodigy 125 points

Hi Joshua,

thanks. I will make some simulations and verify if they fit.

BR,

Javier

0 Joshua Austria 7 months ago in reply to Arijav

TI__Mastermind 24115 points

Hi Arijav,

Sounds good. Feel free to re-open this thread should you need more assistance.

Thank you,

Joshua Austria

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LM5157: Non-isolated buck converters up to 60W