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LM77 SDA pull low to stuck the bus???

George Chen
Intellectual 2175 points
Other Parts Discussed in Thread: LM77

Team,

The description shown at datasheet page11 with figure9.

And my customer did see T_CRIT triggered and to be pulled low.

May I know what LM77 pull low SDA, for what purpose?

And how to solve this problem? Thank you.

  • 0
    TI__Mastermind 36940 points
    Hi George,

    Let me review this, and get back to you.

    Aaron
  • 0
    TI__Expert 4905 points
    LM77 datasheet figure 9 shows the LM77 communicating a zero on the first bit of the second byte of data it is transmitting. If the Host gets an interrupt during this time and does not continue clocking the LM77 it will continue to transmit a zero and keep the SDA line low. Thus, when the Host returns from the interrupt routine it would find a "stuck SDA" line. As the data sheet recommends the best way to recover from this is to have the Host issue clocks until the LM77 releases the SDA line high.

    Take care,