LM5156-Q1: Step up IC solution

Daniel Wang (auto)

Expert 4510 points

Part Number: LM5156-Q1
Other Parts Discussed in Thread: LM5155, LM5156

Tool/software:

Hello team,

Good day.

Here is an IC selection requirement from customer:

Input Typical 12V (9-16)
Output 90V
Output Current, RMS 1.1A

I found LM5156-Q1, but not sure it is the most suitable one, can you recommend the best solution?

Thanks!

over 1 year ago

0 Niklas Schwarz over 1 year ago

TI__Mastermind 34240 points

Hi Daniel,

Thanks for using the e2e forum.
LM5155 and LM5156 are both suitable devices for this application.
However, at minimum Vin of 9V, the required duty cycle to boost to 90V get very high (~90%). This is close the maximum duty cycle the device can handle.
The datasheet lists the limits here:

If customer runs the device at low switching frequency, the device should be able to support a Boost application.
If they prefer higher safety margin or are at risk of even lower Vin, they can consider using a Flyback topology with the same IC and adjust the winding ratio to reduce the required duty cycle.

They can go through some calculation with our quickstart calculators or the Power Stage Designer tool.
https://www.ti.com/product/LM5156-Q1#design-tools-simulation

Please let me know if they have additional questions on the device.
Best regards,
Niklas

0 Daniel Wang (auto) over 1 year ago in reply to Niklas Schwarz

TI__Expert 4510 points

Hello Schwarz,

Thanks for your reply.

About Power Architecture. We need to support 90W (about 90V 1.1A) output after boost, so it is hard for SEPIC/Flyback. So, do you have recommended IC/Design Architecture?

Thank you!

0 Niklas Schwarz over 1 year ago in reply to Daniel Wang (auto)

TI__Mastermind 34240 points

Hi Daniel,

Thanks for the clarification.
As mentioned before, Boost design should be feasible here if they run at low switching frequency (e.g. 100 - 300kHz)

I did check for some reference designs. One example could be this one, which boosts from 6V to 80V, but has lower power ratings. The adjustable output voltage circuit would not be required.
https://www.ti.com/tool/PMP21629

You can check for other suitable designs here:
https://www.ti.com/reference-designs/

Best regards,
Niklas

Power management

Power management forum

LM5156-Q1: Step up IC solution