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TLC5958: Purpose of the 74HC123 monostable on the reference design ?

Timothee Vandeput
Prodigy 10 points
Part Number: TLC5958

Hello,

We are creating our schematics based on the reference design for the TLC5958.

Could you explain what is the purpose of the two monostable (74HC123) used on the schematics?

They are disabling the 74HC138 used to address the power lines, but not sure when it's happening and why.

Thanks a lot

  • 0
    TI__Expert 3190 points

    Hi,

    74HC123 is used to generate EN signal to enable 74HC138 decoders.

    Because A and B control signal are the two low bits for the decoder. the sequence will be 00->01->10->11->00...... with scanning from first line to last line.

    The EN is just active when A, B are changed, at the other time, EN is disable.

    74HC123 can protect the LED board been mis-triggered, which will cause the unexpected lighting up for LED panel.

    Regards!