LMG1020: Maximum frequency

Mike Twieg

Part Number: LMG1020

Hello, the datasheet for this part looks quite exciting but I'm curious as to why its max operating frequency is specified at 60MHz. Its switching characteristics seem to imply it could operate up to 200MHz or even more. Is the stated 60MHz limit due to temperature rise due to power dissipation? If operated in short bursts, would higher frequency operation be possible?

over 6 years ago

0 Lixing Fu over 6 years ago

TI__Expert 3225 points

Hello Mike,

Thanks for asking. The answers for both of your questions are "yes". There is no internal limit for 60 MHz operation. You can drive to higher frequencies as long as you stay within the thermal and other LMG1020 specifications.

Best regards,
Lixing

0 Mike Twieg over 6 years ago in reply to Lixing Fu

Intellectual 960 points

Thanks for the quick answer Lixing.
I notice that the RJA and RJB given in the LMG1020 datasheet seems fairly low. I'm assuming it's for a 2S2P board? What copper weight?

0 Lixing Fu over 6 years ago in reply to Mike Twieg

TI__Expert 3225 points

Hi Mike,

For the test condition of our thermal resistance, please refer to our semiconductor and IC package thermal metrics application report.

www.ti.com/.../spra953c.pdf

LMG1020 is a chip scale IC so the thermal resistance could be lower than typical QFN packages.

Thanks and regards,
Lixing

0 Mike Twieg over 6 years ago in reply to Lixing Fu

Intellectual 960 points

Hi again Lixing,

I've already reviewed that document. The issue is that the LMG1020 gives one value for RJA, but RJA can be measured using either a 1S0P or 2S2P PCB, which will affect the result. Without knowing which PCB type the RJA was measured with, it's not very useful.

Regards,

Mike

0 Lixing Fu over 6 years ago in reply to Mike Twieg

TI__Expert 3225 points

Hi Mike,

I understand your inquiry now. I do not have a detailed test/modeling condition at this moment, but we can check and find out.

Thanks and regards,
Lixing

0 Lixing Fu over 6 years ago in reply to Mike Twieg

TI__Expert 3225 points

Hi Mike,

We used a JEDEC standard JESD51-7 (“high-k”) PCB (2s2p), details are below

1. PCB Size: 114.3 x 76.2 mm
2. 4 Layers: Top and bottom are 2 oz, buried planes are 1 oz
3. Layer size: 74.2 x 74.2 mm
4. No thermal vias

Hope it helps. Thanks!

Lixing

0 Mike Twieg over 6 years ago in reply to Lixing Fu

Intellectual 960 points

Ok, a 2S2P board with 2oz copper on outer layers explains the low RJA.

But I'm surprised at the 2oz copper, since every document I've seen on using chipscale packages (including those from TI) suggest using 1oz or lower copper thickness. Not a huge issue though.

Also while on the topic of the package, do you have any data on light sensitivity for the LMG1020?

Thanks,

Mike

0 Lixing Fu over 6 years ago in reply to Mike Twieg

TI__Expert 3225 points

Hi Mike,

We do not have data regarding light sensitivity.

Thanks,
Lixing

Power management

Power management forum

LMG1020: Maximum frequency