LMH0303: No video from LMH0303

Hi, 

I'm unable to upload circuit image here. Please find the image in the link 

https://drive.google.com/file/d/1ovP2vPVNGvwXF6XsJhSInZEQERSbdWjk/view?usp=drivesdk

Thanks 

Hi Uday, 

Have you tried both 3G and SD signal as an input and there is no output?
As a sanity check, could you measure voltage on VCC pins, RREF, and enable pins?
In addition, could you ensure RST, SCL, SDA pins are floating?

Lastly, is this issue observed on multiple boards and have you tried re-soldering the device?

Best,
J

Hi J,

We have tested only with HD mode.
VCC and Enable pins has 3.3V
RRef is 750R and voltage at this pins is 2.15V
RST, SCL and SDA are flaoting

/RSTO is low ; /fault is low

We have two boards and bothe behave in same way.

Regards
Uday

Hi Uday, 

I just realized that your device is LMH0303. If this is the case, could you read all the register values if possible?
Also, are you pulling SD/HD pin low for HD input signal?

Best,
J

Yeah J, Sorry for the confusion.SD/HDn is pulled low.

No we can't read the registers in the current setup.

Is it essential to configure some registers to get the output?

PS: Can I/you edit the subject?

Hi Uday, 

I see. It looks like all the voltages are normal, so reading registers will help us to understand what is happening inside the IC. 

I edited the subject to LMH0303. 

If reading registers is not possible, we can seek other ways to see what is going on in the IC, but this may take a longer time to debug. 

Best,
J

Hi J,

Let me know the process. Meanwhile I'll find a way to read through I2C.

Can we take this debug through email?

Regards,

Uday

Hi Uday, 

We can keep it here for team visibility. I noticed that SDI input has decoupling capacitors. We typically do not use decoupling capacitors for SDI input. Could you see if shorting the capacitors get the signal across?

Best,
J

Hi J,

We maintained same caps as in our old circuit with GS12190. We referred AN-1972 as well before the design which has decaps. However, we removed the caps and made shorts but no improvement.

Regards
Uday

Hi Uday, 

Thank you for the confirmation. There is a possibility that because the IC is expecting some I2C operations because I2C pins are not pulled high externally. Is it possible to pull these pins up to see if there are any issues/?

Could you also probe the input pin to see if there is input signal going into the IC?

Best,
J

Hi J,

Tried pulling up the I2C lines but no output.

Yes input signal is going to IC.

Regards,

Uday

Hi Uday, 

In this case, could you ship the board to us so we can take a look?

Best,
J