SN65DSI83EVM: I2C SDA Line held low

Hi Navin,

I2C_SDA looks fine at 1.8V on my board. Have you checked to see if the pullup resistor (R4) has been damaged?

Regards,

I.K.

Hi I.K

Please find photos attached. It doesn't look like there is any damage on R4. Could you please suggest any other place to check?

Do you think that the SN65DSI83 chip has failed?

Thanks
Navin

Hi Navin,

Can you remove the shunts on J8 and J9? Looks like these may be pulling the lines down since you also have a shunt on pins 1 and 2 of J12 and J9.

Regards,

I.K.

Hi I.K

We checked the I2C_SDA line when jumper on J12 was completely removed and it still showed 0.35V. if J12 was disconnected, surely J8 will have no effect on the I2C_SDA line?

Have you checked the impedance and continuity on R4? The only ways SDA can get pulled low are if J8 1:2 and J12 1:2 are shunted,  R4 is damaged, or the device itself is damaged.

Regards,

I.K. 

Hi IK

I will have to come back to this issue later as I'm working from home, I will give you the answer in the next few days

Thanks
Navin

Hi IK

We measured resistance across these points:

1P8V to SCL (J9-2) = 4.6948K

1P8V to SDA (J12-2) = 4.6355K

This suggests to me that the value of R4 is correct and there is no damage to that resistor?

The jumpers were in the exact same positions as shown in the below photo

Thanks

Navin

Hi Navin,

Ah, I didn't notice the jumpers were hanging off 1 pin. But yes R4 looks correct so that's not the problem, as it will pull SDA up to 1.8V. Is SCL stuck low as well? 

Regards,

I.K. 

Hi IK

SCL is not stuck low, that stays at 3.28V. It is only SDA that goes low

Thanks

Navin

Hi Navin,

I mean the I2C_SCL net. Is this pulled up to 1.8V or is it stuck low? You mentioned in your original post that SDA was 3.28V as well, but those nets are not directly connected to the device.

Regards,

I.K. 

Hi IK

Apologies for the confusion, Yes the I2C_SCL net is pulled up to 1.79V, which was measured on the middle pin of J9.

Thanks

Navin

Hi Navin,

I don't see any other reasons for SDA to be stuck low aside from a damaged device. Is it possible for you to replace the device on the board?

Regards,

I.K.

Hi IK

I had initially tried to return this EVM, due to the possibility that the device was faulty. The return was declined and I was put in touch with TI Customer support.

Return ID was CPR211051099

TI Customer support Case CS0455287

SO# T01081572

Would it be possible to return the EVM, as it is very likely that the device is faulty?

Thanks

Navin

Hi Navin,

I don’t have any visibility in the return process. I recommend that you contact your local TI sales office for assistance with returns as well as obtaining a replacement EVM.

Regards,

I.K.