LP87524P-Q1: Looking at a radar design using LP87524P PMIC device

Gerald

Part Number: LP87524P-Q1
Other Parts Discussed in Thread: AWR2243, MMWCAS-RF-EVM, AWR6843AOP

Hi Experts,

Our customer is looking at a radar design using LP87524P PMIC device. The device states it can do 10A total, but for each buck channel it seems to define current limits of 3A, 1.5A, 3A and 2.5A for buck 0,1,2,3. Is it ok to use the device if his currents are 2A, 2A,2A,2A for Buck 0,1,2,3 This is still less than 10A in total?

See page 14 in the datasheet. he assumes because his total current is 8A that he should be ok to use this device.

As far as I am aware, correct operation is not guaranteed if any of the operating conditions are exceeded.

But now he don’t understand how on the MMWCAS-RF-EVM board which uses two LP87524P devices to power 4x AWR2243 devices, two on one LP87524. The AWR2243 states on the 1.2V VDDIN, VIN_SRAM, VNWA = 850mA max. The LP87524 uses Buck1 which is 1.5A but 2 x 850mA for the AWR2243 = 1.7A. What are we missing?

https://www.ti.com/tool/MMWCAS-RF-EVM?keyMatch=MMWCAS-RF-EVM&tisearch=Search-EN-technicaldocument&usecase=part-number

The customer's actual issue is that he is trying to design a 4x AWR6843AOP system and he was going to copy the power scheme from the MMWCAS-RF-EVM but came across the above issue and that’s why he queried the total power consumption on the LP87524P.

Therefore, his question is this, can he use two LP87524P devices to power 4x AWR6843AOP? If the answer is no what is your recommendation? Please advice. Thank you.

Best regards,
Gerald

over 2 years ago

+1 Daniel W over 2 years ago

TI__Genius 13216 points

Hi Gerald,

It is generally recommended to have 1A of space between the max DC current consumption and the ILIM setting for the buck.

However, since the MMWCAS-RF-EVM is a validated design, no issue is expected in this use case.

Thanks,

Daniel W

0 Gerald over 2 years ago in reply to Daniel W

TI__Genius 9570 points

Hi Daniel,

I'm still unclear with your response whether YES the LP87524P can be used to power two AWR6843AOPs or NO it can't especially around the 1,2V

Please clarify with a YES or NO?

Regards,

Gerald

0 David Martinez over 2 years ago in reply to Gerald

TI__Intellectual 2101 points

Hey Gerald,

Daniel is out of office today due to US holiday. They will be back Monday to look over your inquiries.

Best,

David

0 Daniel W over 2 years ago in reply to David Martinez

TI__Genius 13216 points

Hi Gerald,

MMWCAS-RF-EVM is a validated design as stated earlier so it is a supported use case.

Thanks,

Daniel W

0 Gerald over 2 years ago in reply to Daniel W

TI__Genius 9570 points

Hi Daniel,

So this means YES the LP87524P can be used to power two AWR6843AOPs?

Best regards,
Gerald

+1 Daniel W over 2 years ago in reply to Gerald

TI__Genius 13216 points

yes

0 Gerald over 2 years ago in reply to Daniel W

TI__Genius 9570 points

Hi Daniel,

Many thanks for your response. That’s good news for the customer.

But can I just check when you state “MMWCAS-RF-EVM is a validated design as stated earlier so it is a supported use case.” The MMCAS-RF-EVM board uses AWR2243 device NOT AWR6843AOPs.

I will assume your statement “YES the LP87524P can be used to power two AWR6843AOPs” is still ok and so the customer will proceed with his design using these devices.

Regards,
Gerald

+1 Daniel W over 2 years ago in reply to Gerald

TI__Genius 13216 points

Hi Gerald,

The risk here is that during large load step conditions the current limit of BUCK1 may be reached. This risk can be mitigated by additional POL capacitance.

I do not expect issue with using this device

Thanks,

Daniel W

Power management

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LP87524P-Q1: Looking at a radar design using LP87524P PMIC device