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About tlc5917's power-up

Jacky Wang23
Prodigy 50 points
Other Parts Discussed in Thread: TLC5917

In the Application Document:<555 timer eliminates LED driver’s need for microprocessor control>,there is context about the TLC5917's power-up, which is copied as follows: 'At power-up, the internal on/off latches that turn each output on or off default to zero, so you must set these latches to one before the outputs turn on. The 555 timer replaces the microprocessor for this function.'

My question is: (1)Do on/off Latches mean  in the data sheet? (2)What does 'set these latches to one' mean? What should be noticed in the Control Signal's Sequences?

  • 0
    TI__Expert 3460 points
    Hi Jacky,

    Thanks for the question. The app note is referring to the fact that the TLC5917 works similar to a shift register, and the Latch Enable (LE) and Output Enable (OE) pins are control signals. You use the LE pin to latch the data into the device's registers. The OE pin is used to turn on the output, but this is an active low pin. Overall, if you set the LE pin high and the OE pin low, the 555 timer can be configured to clock in all of the outputs high.

    I would refer to the datasheet if you have further questions, but would be happy to talk about this implementation more.