IWR6843: POE Powered (+48V)

Mike Schell

Part Number: IWR6843
Other Parts Discussed in Thread: LMR38020, TPS7A92, LP87745-Q1

Dear E2E Support-

I am working on an IWR6843 radar design that uses 48V POE non-isolated power. I am trying to find the best power supply solution.

My current best solution is 48V -> LMR38020 switcher -> 3.4V -> TPS7A92 low-noise LDO -> 3.0V -> LP87745-Q1 triple buck (1.8V, 1.2V, 1.0V).

Do you have any recommendations or changes to this approach?

Thanks-

Mike Schell

over 1 year ago

0 Ankit Mohanty over 1 year ago

TI__Expert 7300 points

Hi Mike,

We are looking into query , can you please share the Power Distribution Network schematic.

Regards

Ankit

0 Mike Schell over 1 year ago in reply to Ankit Mohanty

Prodigy 170 points

Hi Ankit-

I don't have the schematics yet, but here's a block diagram showing the components and output voltages.

Hope this helps-

Mike

0 Ankit Mohanty over 1 year ago in reply to Mike Schell

TI__Expert 7300 points

Mike,

Thanks, this shall help. Will check and get back to you.

Regards

Ankit

0 Ankit Mohanty over 1 year ago in reply to Ankit Mohanty

TI__Expert 7300 points

Hi Mike,

When taking into account the highest switching frequency of 2.2MHz and the maximum Ton(On Time) value of 130ns in the LMR38020, the minimum duty cycle is 28.6%. While you would need a duty cycle of 7.08% to create 3.4 of 48V, which is not feasible.

Regards

Ankit

0 Mike Schell over 1 year ago in reply to Ankit Mohanty

Prodigy 170 points

Hi Ankit-

Thank you for the analysis. Could I run the LMR38020 at 300KHz and then use the TPS7A92 LDO to clean up the ripple? The LDO ha good ripple rejection at the lower frequencies.

Or, can you suggest a better overall approach?

Thanks-

Mike

0 Ankit Mohanty over 1 year ago in reply to Mike Schell

TI__Expert 7300 points

Hi Mike,

The maximum input range of TPS7A92 is 6.5V. Can you please confirm the input voltage to TPS7A92 when LMR38020 is operated at 300KHz.

Regards

Ankit

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IWR6843: POE Powered (+48V)