LM5023: Application design does not match application note

Barend Smits

Part Number: LM5023

Hello,

The TI page shows a clear application note for the LM5023 in a design called PMP8677. In the LM5023 datasheet Pin 4 (comp) is connected to gnd through a cap. In the PMP8677 design this cap, C15 seems to be replaced by a part with a value 49.9k. This suggest a resistor. Can you conform and clarify?

As well,
In the LM5023 datasheet pin 5 is connected through a 499 Ohm resistor (R17). In the PMP8677 design this value is suddenly 4.99k. Which is correct?

And to continue,
A quick evaluation of this design could really help. Can gerbers for this board be made available?

Thanks!!

over 6 years ago

0 Eric Faraci over 6 years ago

TI__Expert 8210 points

Barend

C15 is used to filter out noise on this pin. Our documentation has an error and incorrectly shows a resistance for this capacitor value. I've reached out to the designer of PMP8677 to correct this.

The example design in the LM5023 datasheet and PMP8677 have different design targets so it's expected that some parameters are different between the two. R17 in the datasheet and R15 in PMP8677 are both also referred to as REXTERNAL in the LM5023 datasheet. Section 8.2.2.2 (page 21-25) goes into detail explaining why this resistor is needed and how to calculate it.

I've attached the gerber, NC dril and ODB files for PMP8677.

Best Regards,

Eric

PMP8677 Fab.zip

0 Barend Smits over 6 years ago in reply to Eric Faraci

Prodigy 30 points

Hello Eric,

Thank you for your excellent and fast answer. Highly appreciated!

0 Eric Faraci over 6 years ago in reply to Barend Smits

TI__Expert 8210 points

Barend

I got clarification from the designer for PMP8677. On the board used a resistor with a resistance of 49.9k was used where C15 is. The schematic symbol is incorrect, it should be a resistor.

Best Regards,

Eric

0 Barend Smits over 6 years ago in reply to Eric Faraci

Prodigy 30 points

Hello Eric,

Thanks again.!

regards,

Barend

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LM5023: Application design does not match application note