LM3674: LM3674MF-ADJ (ADJ version)

Jonathan Navor

Part Number: LM3674

Hi Team,

Greetings! We need your assistance for the customer's inquiry below.

We are using LM3674 -adj version of the device in our design to generates 1.2V from 3.3V power supply. We have 280K and 200K as standard Feedback Resistors in design. The complete calculation is based on Vref of 0.5V. But the boards which we received from our Local CM show 0.6V as Vref and hence we have to change the feedback value to get 1.2V. The Value measured at pin 4 (FB) is 0.6V under fail condition. Changing the value to same R1 = R2, we got 1.2V what we expecting. However this is different from the datasheet and hence need your input on it.

We are looking forward to your response and thank you in advance for the support.

Best regards,

Jonathan

over 3 years ago

0 Excel Regidor over 3 years ago

TI__Mastermind 30456 points

Hi Jonathan,

Apology for the late response.

You are correct. The FB voltage should be 0.5V as specified in the datasheet. Does all the samples have the same behavior (VFB = 0.6V)?

I need your help to check the body marking if it is "SLTB". If not, then it might be a different part and you should return all parts to the local CM.

Best regards,

Excel

0 Excel Regidor over 3 years ago in reply to Excel Regidor

TI__Mastermind 30456 points

Hi Jonathan,

Just a soft reminder.

1. Does all the samples have the same behavior where VFB is regulating at 0.6V?

2. Is the body marking "SLTB" correct?

Looking forward for your feedback.

Best regards,

Excel

0 Jonathan Navor over 3 years ago in reply to Excel Regidor

TI__Genius 9475 points

Hi Excel,

Here is our customer's response below:

Till now we had received total (5+3) boards and the issue is same in all eight boards. I checked the image and t is highlighting the code SLTB. I am attaching the image for the same here. This is no a new parts. We are using same part but module used to assembled at China CM location where voltage are OK. I am getting precise 1.2V. While working with local CM, hyderabad we got 1.4V for the same resistor network. Then we acknowledge the issue of 0.6V Vref.
Awaiting you input here.................

Thank you for your response,

Jonathan

0 Excel Regidor over 3 years ago in reply to Jonathan Navor

TI__Mastermind 30456 points

Hi Jonathan,

Thanks for the update.

Can you send a waveform which include VIN, VFB and VOUT? Use two time/div oscilloscope settings (1.0us and 1.0ms).

In parallel, I suggest to send some of the samples to local TI office for failure analysis.

Best regards,

Excel

0 Excel Regidor over 3 years ago in reply to Excel Regidor

TI__Mastermind 30456 points

Hi Jonathan,

Just a soft reminder.

Any feedback on the requested waveforms?

Best regards,

Excel

0 Excel Regidor over 3 years ago in reply to Excel Regidor

TI__Mastermind 30456 points

Hi Jonathan,

I will close this thread because it has been open for a while, and I didn't receive your feedback.
You can re-open the thread again by posting your comments.

Thank you.

Best regards,

Excel

Power management

Power management forum

LM3674: LM3674MF-ADJ (ADJ version)