LM25143: spec check

GARETH OU

Guru 12185 points

Part Number: LM25143

Tool/software:

Can the LM25143 VCCX be connected directly to an external 5V supply to lower the IC Temperature?

7 months ago

0 Naresh Adepu 7 months ago

TI__Mastermind 18700 points

Thanks for your question. I will look into it and get back to you

Thanks and Regards

Naresh

0 Naresh Adepu 7 months ago in reply to Naresh Adepu

TI__Mastermind 18700 points

Hello Gareth,

Yes, LM25143’s VCCX pin can be directly connected to a regulated external 5V supply to lower IC temperature and improve efficiency. Please ensure:
• The external 5V does not exceed 6.5 V at any time, per absolute maximum ratings.
• VIN must always be higher than the external 5V bias to prevent reverse currents and possible device damage
• Using external bias is a valid method to bypass internal regulator dissipation and is recommended for thermal performance
Refer to the LM25143 datasheet for detailed recommendations and ensure all system conditions stay within the specified ratings

Thanks and Regards

Naresh

0 GARETH OU 6 months ago in reply to Naresh Adepu

Guru 12185 points

Hi Naresh

Could you please help me confirm the LM25143 circuit? Will adding inductance (for EMI) to the VIN terminal affect the circuit phase difference? Is it necessary to add a large capacitor to the input terminal to solve this problem?

0 Naresh Adepu 6 months ago in reply to GARETH OU

TI__Mastermind 18700 points

Thanks for your question. I will look into it and get back to you

Thanks and Regards

Naresh

0 Onkar Bhakare 6 months ago in reply to Naresh Adepu

TI__Mastermind 24262 points

Hello Gareth

You’ll need to provide damping if you use an inductance at the input. This can be achieved by adding either an electrolytic capacitor at the input or a series resistor with a multilayer ceramic capacitor (MLCC).

For a more detailed explanation and guidance, please refer to the application note:

https://www.ti.com/lit/an/snva538/snva538.pdf?ts=1760594843643&ref_url=https%253A%252F%252Fwww.google.com%252F

Regards

Onkar Bhakare

0 GARETH OU 6 months ago in reply to Onkar Bhakare

Guru 12185 points

Hi Onkar Bhakare

Could you help check the LM25143 schematic and any need to adjust

The VIN terminal has been changed to a single inductor, with a 220uF capacitor after the inductor.

Thanks

0 Onkar Bhakare 6 months ago in reply to GARETH OU

TI__Mastermind 24262 points

Hello Gareth

Could you please share filled QuickStart for detailed review?

Thank you

Regards

Onkar Bhakare

0 GARETH OU 6 months ago in reply to Onkar Bhakare

Guru 12185 points

Hi Onkar Bhakare

Please see the attachment below

LM(2)5143-Q1 quickstart design tool - revB2.zip

0 Onkar Bhakare 6 months ago in reply to GARETH OU

TI__Mastermind 24262 points

Hello Gareth

Here are some comments

Selected inductor value is too low, setting ripple current 120% of full load current and it's not meeting recommend inductance value from slope compensation point of view
PM looks good, make sure you are using right ESR value in the output capacitors section. USE ESR values of EL cap only
Ensure equivalent Thevenin resistance of feedback network is higher than 5 kOhm
Tie VCCX to AGND if it is unused.
238A FETs will quite overdesign for 20A application, lower current FET can be chosen so Qg will be lower and thus lower switching loss