UCD9090A: UCD9090A Acknowledgment Failure During Device Information Reading

H R Lavanya

Part Number: UCD9090A

Tool/software:

Hi,

We would like your support in resolving an issue with reading device information from the UCD9090A, where the master device is the NXP MIMX8.

We have observed a consistent failure of ACK responses at a clock frequency of 100 kHz and inconsistent ACK responses at 64 kHz. For reference, please see the attached image (i2c_freq_004).

Our design includes four slave devices, including the UCD9090A, connected to a single I²C bus with a 2.2 kΩ pull-up resistor placed near the master device on the board. No series resistors are used for isolation, and testing with only the UCD9090A as the load produced the same issue. The board is currently running at a clock frequency of 64 kHz.

The total load capacitance of the bus is:

SDA: 60.896 pF
SCL: 61.168 pF

The observed rise and fall times at 64 kHz are:

SCL:

Rise: 416 ns
Fall: 20 ns

SDA:

Rise: 428 ns
Fall: 20 ns

Additionally, we found a similar issue discussed in the TI Forum. The related thread has been attached for your reference.

We appreciate your guidance on resolving this issue. ( https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1224180/ucd9090a-ucd9090a/4651400?tisearch=e2e-sitesearch&keymatch=UCD9090A#4651400 )

Thanks & Regards,

Lavanya

7 months ago

0 Troy Johnson 7 months ago

TI__Expert 4225 points

Hi,

I will need some time to look into this behavior. I will get back to you by, or before, Monday the 27th.

Regards,

Troy

0 H R Lavanya 7 months ago in reply to Troy Johnson

Prodigy 10 points

thank you. Will be waiting for your response.

0 H R Lavanya 7 months ago in reply to Troy Johnson

Prodigy 10 points

Hi,

Is there any update on this issue?

0 Troy Johnson 7 months ago in reply to H R Lavanya

TI__Expert 4225 points

Hi,

Can you provide details on what commands / command format this behavior is seen with? Is it seen with all commands, or just certain ones?

Also, wanted to confirm:

Have you seen this same behavior when using the TI USB adapter to connect with the UCD device?
Does the bus master support clock stretching?

Regards,

Troy

0 H R Lavanya 7 months ago in reply to Troy Johnson

Prodigy 10 points

This is seen with the SMBUS command to read the device ID (0xFD). We could try other commands, if needed with the i2c transfer command.

Have you seen this same behavior when using the TI USB adapter to connect with the UCD device? - No
Does the bus master support clock stretching? Yes

+1 Troy Johnson 7 months ago in reply to H R Lavanya

TI__Expert 4225 points

Hi,

Since there are no issues when using the TI USB adapter, there does not appear to be any issue with the UCD9090A device itself, only with communication with between it and this specific master device.

I suggest comparing the SCL and SDA waveforms when using the board master and using the TI USB adapter, to try and determine any difference that can cause a NACK in one case but not in the other. You can use a logic analyzer for this as well, if one is available, to check that the command is being sent in the expected format.

Regards,

Troy

0 H R Lavanya 7 months ago in reply to Troy Johnson

Prodigy 10 points

Okay, I'll check the testing as mentioned.

Thanks & Regards,

Lavanya

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UCD9090A: UCD9090A Acknowledgment Failure During Device Information Reading