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PCA9515A: Pulse Error Issue

Jim CHEN
Expert 4795 points
Part Number: PCA9515A
Other Parts Discussed in Thread: PCA9515B

Dear Team,

We found problem in our manufacture line, some of system can’t read our PSU info through PMbus which used I2C bus repeater PCA9515A.

In the below waveform, we can see that there is a pulse in the green circle.

This pulse would cause the error of PSU to reply the ack message to BMC.

We didn’t find such issue on other vendor part.

Please help to advice.

Topology as below

Other vendor P2P solution

  • 0
    TI__Guru 73271 points

    Hey Jim,

    It looks like the slave (PSU?) is pulling the line low on the clock (clock stretching). There is some errata in the datasheet that suggests that clock stretching causes overshoot:

    Has the customer tried to use our PCA9515B device instead of the A version? I don't see the errata discussed in the B version.

    Also, is the customer able to place a small series resistor on SDA/SCL side 1? (something like 10~20 ohms) This may help dampen the swing.

    Thanks,

    -Bobby