• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 62 subscribers
  • Views 224 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLC5948A: Can GSCLK and LAT be controlled by one signal from controller for just LED on/off control?

Kazuya Nakai59
Guru 20620 points
Part Number: TLC5948A
Other Parts Discussed in Thread: TLC5948, TLC59283, TLC5929

Hello guys,

One of my customers is evaluating TLC5948A for just LED on/off control because they don't need PWM dimming for their next products.
Their controller is poor. So they can use three GPIO ports only and they can not supply GSCLK signal separately.

At this moment, they control SIN and SCLK by two GPIO ports. They tie LAT and GSCLK together and control those signal by remaining one port.
They control LED turn on/off by BLANK bit of the function control latch data bit 119.
For LED turning on, they wrote non zero data to GS data latch at first. After that, they wrote "0" to BLANK bit. Then LED was turned on.
For LED turning off, they wrote "1" to BLANK bit. Then LED was turned off.

At this moment, they have the following question. Could you please give me your reply?

Q. This result is good for them. 
     But is this control method not problem?

Best regards,

Kazuya.

 

.

  • 0
    TI__Genius 12915 points

    Hi Kazuya,

    Yes this control method should be OK and I do not have other concern.

    But I wonder why customer choose TLC5948 for such usage. we have some simply 16-channel on/off device like TLC59283 or TLC5929.

  • 0 in reply to Hardy Wu
    Guru 20620 points

    Hi Hardy,

    Thank you very much for your helpful reply.

    As you say, the customers looked for just on/off LED driver like TLC59283/29 and so on.
    But those LED drivers lead time are very long and they knew they couldn't get any driver by their dead line for mass production starting date.
    Then they found TLC5948ADBQR stock and they have purchase some reels of the device.

    Could I ask you an additional question as the follow?

    Q. According to TLC5948A datasheet, tSU2:LAT↑ for BLANK bit '0' set to GSCLK↑ needs 50ns.
        The setup time is not guaranteed when LAT and GSCLK are tied together.
         I think that 1'st GSCLK may not be countered by GS counter. So 2'nd GSCLK is needed to input to ensure OUTn turn on.

        My understanding correct?
        2'nd GSCLK is sufficient to to ensure OUTn turn on?

    Thank you again and best regards,

    Kazuya. 

  • 0 in reply to Kazuya Nakai59
    TI__Genius 12915 points

    Hi Kazuya,

    Yes there have some delay time for blank function effective, after latching the control data with blank bit to the device. The first GSCLK pulse, which is intended for latch signal, cannot be counted into the GS counter. There for additional GSCLK pulse need to be sent. Between the 1st GSCLK and 2nd GSCLK, there should not have SCLK signal, to keep the data in the shift register unchanged.

  • 0 in reply to Hardy Wu
    Guru 20620 points

    Hi Hardy,

    Thank you very much for your reply and I'm sorry to be late my response.
    Your reply is very helpful for the customer and me.
    Thank you again and best regards,

    Kazuya.