SN74LV4T125: Some output of this buffer is not correct !

Vidhi Patel

Prodigy 20 points

Part Number: SN74LV4T125

Tool/software:

Hi TI,

I am using this buffer between microcontroller and Gate driver.

Right now I have only microcontroller board, and a buffer at the output.

The output of this buffer goes to R = 10k,

Some pins are as marked in Image1 are working and some are giving output as shown in image2.

Yellow is input(3A) and green is output of the same channel (3Y)

Can you please help me understand, why some are working but then some of same buffer connected in same fashion are not working fine.

Also how to debug advance ? I have done initial checks like Vcc, pull up R, pull down R, RC network.

Thank you,

over 1 year ago

0 Michael Ikwuyum over 1 year ago

TI__Guru 51346 points

Hi Vidhi,

I believe only the waveform not working is shown and not the waveform working. I suspect the pins not working are connected with the R.

I would recommend to disconnect all load at the output to help verify while comparing differences in components connected to the working/not working pins, thanks.

Best Regards,

Michael.

0 Vidhi Patel over 1 year ago in reply to Michael Ikwuyum

Prodigy 20 points

please see pins input and output working.

Also, I have removed Rs from all pins and checked but still it is same.

0 Michael Ikwuyum over 1 year ago in reply to Vidhi Patel

TI__Guru 51346 points

Hi Vidhi,

Could you help share schematic highlighting components and test points as I do not see Rs or other components?

Thanks,

Michael.

0 Vidhi Patel over 1 year ago in reply to Michael Ikwuyum

Prodigy 20 points

I apologize but I am not sure if i can share the schematics, but i can try to explain as below

I have a DSP board: which has 28377S, which is outputting PWM, going to buffer (which is also translating PWM from 3.3V to 5 V), this 5 V is going out header. this Header is connecting DSP board to another board(lets called it testing board), which is made specially for testing DSP board. RN1, RN2, RN3 are 10k resistors are mounted on testing board, which is connecting output of buffer and ground. I am measuring output PWM signals from buffer at test points connected to RN1, RN2, RN3 (marked in red)

+1 Clemens Ladisch over 1 year ago

Guru 317060 points

The output's high level is about 2.5 V, which suggests that the output is shorted to another output that drives low.

We cannot help you without a real schematic.

0 Vidhi Patel over 1 year ago in reply to Clemens Ladisch

Prodigy 20 points

hi Clemens, your analysis was right, I checked pull down R and they were short.

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SN74LV4T125: Some output of this buffer is not correct !