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DS90UB926Q-Q1 Wrong Address

Andrew Stewart82
Prodigy 60 points

Other Parts Discussed in Thread: DS90UB926Q-Q1

Hello,

I'm trying to debug an issue on a DS90UB926Q-Q1 where the expected 7'b address is 0x39 and the actual address is 0x3A.

Most of the hardware that we built works as expected but some of them are defaulting to 0x3A instead of 0x39.  I'm just wondering where I should look.

Like the datasheet shows on page 32 we have a 137k ohm resistor for R1 and a 191k ohm resistor for R2.   Ideal VR2 measure at 1.902V and VDD33 measure at 3.235V for an ideal ration of ... 0.588.

Where should I look, when does this IDx pin 56 get read?  Rising edge of PDB?

Andrew

  • 0
    TI__Genius 14015 points
    Hi Andrew,

    The IDx pin is read immediately after PDB goes high, within the first two milliseconds. It's important that the supplies have settled when PDB goes high.

    Are you using 1% tolerance resistors?

    Thanks,
    Jason
  • 0 in reply to Jason Blackman
    Prodigy 60 points
    Thanks Jason,

    I am using 1% resistors and I'll double check to ensure that the delay is long enough for the supply to settle. Is VDD33_B specifically the pin I should be measuring the voltage on?

    How close to the ideal ration do I need to be? If 0.583 is the ideal ratio for address 0x39, at what ratio will the address flip to 0x3A?

    I'm going to look at nudging up R1's resistance a bit to get the ratio to be as close to the ideal as possible.

    Andrew