TLC5941: Clarification on Extra SCLK Pulse

Simon Sultana

Prodigy 10 points

Part Number: TLC5941

Tool/software:

Dear TI Support Team,

I need clarification on the use of the additional SCLK pulse in the TLC5941 LED driver:

Is the extra SCLK pulse required only for GS data cycles, or also for DC data cycles?
What is the purpose of this extra SCLK pulse?
Is the extra SCLK pulse required after XLAT when transitioning from GS to DC mode?
Is the extra SCLK pulse required after XLAT when transitioning from DC to GS mode?
In the case of continuous GS cycles (e.g., multiple GS cycles in succession without switching to DC mode), is the extra SCLK pulse needed after each XLAT signal?
How should the extra SCLK pulse be handled during initial setup after power-on, when GS data must be set before DC data?

Thank you for your assistance.

Best regards,
Simon

over 1 year ago

0 Jared Zhou over 1 year ago

TI__Mastermind 20515 points

Hi Simon,

Please give me some time and I will reply you later since I am OoO these days.

BR, Jared

0 Simon Sultana over 1 year ago in reply to Jared Zhou

Prodigy 10 points

Hi Jared,

Do you have an answer please?

Simon

0 Jared Zhou over 1 year ago in reply to Simon Sultana

TI__Mastermind 20515 points

Hi Simon,

Do you mean the extra CLK is the GSCLK? Could you please tell me how or where you found TLC5941 needs a extra CLK?

BR, Jared

0 Simon Sultana over 1 year ago in reply to Jared Zhou

Prodigy 10 points

Hi Jared,

In the datasheet it is ambiguous. The timings show that an extra '193rd' SCLK cycle is needed after every GS cycle (https://www.ti.com/lit/gpn/tlc5941)(Figure 12 pg 13):

But it then mentions that an extra SCLK cycle is only needed for the first GS data input cycle after dot correction (Pg 19):

In the two example scripts available, one of them adds an extra SCLK after every GS cycle (6567.TLC5941 Sample Code.zip):

But in the assembly language example, it only sends it once (https://www.ti.com/lit/pdf/slva267) :

Which is the correct?

Thanks and Regards,

Simon

0 Zhiqian Wu over 1 year ago in reply to Simon Sultana

TI__Mastermind 31255 points

Hi,

Our expert will give you a feedback tomorrow.

0 Jared Zhou over 1 year ago in reply to Simon Sultana

TI__Mastermind 20515 points

Hi Simon,

I think every GS cycle needs an extra SCLK. The first example should be right. For the second example, I think the reason that it only sends it once is because the system only has 1pcs TLC5941.

BR, Jared

0 Simon Sultana over 1 year ago in reply to Jared Zhou

Prodigy 10 points

Hi Jared,

In the datasheet, Figure 12 refers to the timings for 1 piece of TLC5941, and it shows an SCLK cycle for every GS cycle (Figure 14 is for 2 pcs TLC5941). However, on Page 19, it mentions that an extra SCLK cycle is only needed for the first GS data input cycle after dot correction, and not for all GS cycles. This seems inconsistent. Could you clarify this?

Thanks and Regards,
Simon

0 Zhiqian Wu over 1 year ago in reply to Simon Sultana

TI__Mastermind 31255 points

Hi, Simon

Our expert will give you a feedback tomorrow.

0 Jared Zhou over 1 year ago in reply to Simon Sultana

TI__Mastermind 20515 points

Hi Simon,

Sorry for the late reply due to the sick leave before, and for the question you mentioned above, I am sorry that I think I was wrong before. Your understanding for the extra SCLK is correct.

BR, Jared

0 Simon Sultana over 1 year ago in reply to Jared Zhou

Prodigy 10 points

Hi Jared,

I'm not sure what you mean by my understanding for the extra SCLK is correct. I need a clarification for the inconsistency in the datasheet since it is contradicting as I already mentioned previously.

Simon

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TLC5941: Clarification on Extra SCLK Pulse