LMR14030-Q1: LMR14030SDDAR Hardware review schematic

Manjunath G14

Expert 2075 points

Part Number: LMR14030-Q1
Other Parts Discussed in Thread: TLV1805-Q1, LM74700-Q1

Hi TI team,

Please find the attached circuit diagram of LMR14030SDDAR power supply and kindly review the same and share your valuable comments on it to improve the design.

Input : 7.5V to 40VDC

Output : 3.8V DC/3.5A

and also please suggest a N-MOSFET for input polarity protection for the same supply.

Thanks

Regards,

Manjunath

Hardware design engineer

over 5 years ago

0 Ethan T over 5 years ago

TI__Expert 3835 points

Hi Manjunath,

Place a 0.1uF input capacitor close to the vin pin for high-frequency filtering if possible. I would also recommend some combination with ceramic output capacitors as well to lower the ESR of your output. Make sure to follow section 8.2.2.4 of the datasheet to make sure that output ESR is within your output specifications.

To clarify, the fb resistors are for a 5V output where the schematic also labels a 3.8Vout.

Regards,

Ethan

0 Manjunath G14 over 5 years ago in reply to Ethan T

Expert 2075 points

Hi Ethan,

Thanks for the review.

1. At the input, parallel to 4.7uF you are suggesting to add 0.1uF?

2. you mean to say:To add some ceramic capacitor parallel to 56uF Electrolytic capacitor?

3. 8.2.2.4 section is not there in the datasheet : http://www.ti.com/lit/ds/symlink/lmr14030.pdf

4. The output voltage is 5V.(Wrongly mentioned in the above circuit)

0 Ethan T over 5 years ago in reply to Manjunath G14

TI__Expert 3835 points

Hi Manjunath,

1. Yes

2. Yes

3. Please see automotive datasheet: https://www.ti.com/lit/ds/symlink/lmr14030-q1.pdf

4. Okay

Thanks,

Ethan

0 Manjunath G14 over 5 years ago in reply to Ethan T

Expert 2075 points

Hi Ethan,

For designing this I have used TI workbench, Attached is the simulated design from the workbench,

and I have followed the same, Please check and confirm.

0 Manjunath G14 over 5 years ago in reply to Ethan T

Expert 2075 points

Please find my below reply,

and also request you to Please suggest Polarity protection and over voltage protection for 24V battery powered system

0 Ethan T over 5 years ago in reply to Manjunath G14

TI__Expert 3835 points

Hi Manjunath,

The design will work as expected, but the capacitors I suggested are best practices for switching regulators. Without any output ceramic capacitors, you allow the large ESR to dominate the output voltage ripple. If you are okay with the expected voltage ripple, then the design should work fine.

TVS diodes are commonly used for over voltage battery transients. The LM74700-Q1 is a smart diode controller or the TLV1805-Q1 is a comparator commonly used for reverse battery and over voltage protection.

Regards,

Ethan

0 Manjunath G14 over 5 years ago in reply to Ethan T

Expert 2075 points

Understood Ethan,

for adding 0.1uF ceramic cap at the input and output, please suggest me how much voltage range to be selected for the both,

0 Ethan T over 5 years ago in reply to Manjunath G14

TI__Expert 3835 points

Hi Manjunath,

Use X7R capacitors for good derating. I would suggest >50V for the input and >16V for the output.

Regards,

Ethan

0 Manjunath G14 over 5 years ago in reply to Ethan T

Expert 2075 points

Hi Ethan,

Please find the attached updated circuit and check for the final time.

C1206C104MMRECLR

0.1uF/63V/X7R

CGA3E2X7R1E104K

0.1uF/25V/X7R

Thanks

0 Ethan T over 5 years ago in reply to Manjunath G14

TI__Expert 3835 points

Hi Manjunath,

The design looks okay to me. I would recommend going through the applications section in the datasheet to confirm as well.

Regards,

Ethan

0 Manjunath G14 over 5 years ago in reply to Ethan T

Expert 2075 points

Thanks Ethan,

Thanks for all your review comments to improve the design,

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Power management forum

LMR14030-Q1: LMR14030SDDAR Hardware review schematic