Low-noise LED drivers and PWM

Torje Nikolai Thorsen

Other Parts Discussed in Thread: TLC5929, TLC5926, TLC5922

Hi,

I am looking for a LED driver with dimming capability for use in an audio product. The LED driver must not generate switching noise, so I want to avoid chips with PWM-control.

I have identified two suitable chips for my application: TLC5926 and TLC5929. Both chips have dimming capability, in form of a 256-step "global current gain" for the TLC5926 and a 128-step "global brightness control" for the TLC5929. Could you please explain briefly how this adjustment is implemented in the chip? Is this adjustment carried out by means of pulse width modulation (PWM) or other switching techniques, or is it purely analog?

Maybe you have other suitable chips to suggest for a lowest possible noise signature?

Best regards,

Torje

over 9 years ago

0 Feifei Shen over 9 years ago

TI__Expert 3275 points

Hi Torje,

For tlc5929, you can adjust the current by setting different "global currrent gain", it's a pure analog method withour switching. The current amplitude can be changed.

Best regards,

Feifei

0 Torje Nikolai Thorsen over 9 years ago in reply to Feifei Shen

Intellectual 520 points

Hi Feifei,

Thank you for your quick response. That is very positive. But what about TLC5926?

Best regards,

Torje

0 Feifei Shen over 9 years ago in reply to Torje Nikolai Thorsen

TI__Expert 3275 points

Hi Torje,

TLC5926 should be the same as tlc5929.

BTW, the function of global brightness control can only adjust the amplitude of current by all 16 channels. You can't control each channel separtely.

If you want to control each channel separetly by anolog method, pls refer to tlc5922/3/4, dot correction funtion.

Best regards,

Feifei

0 Torje Nikolai Thorsen over 9 years ago in reply to Feifei Shen

Intellectual 520 points

Hi Feifei,

Thanks a lot for your help and your quick response. A global control is all I need, so I will go for the TLC5926.

By the way, I'm intending to use the chip on a shared SPI bus for the serial communication. The TLC5926 is not explicitly marked as "SPI compatible", (unlike the TLC5922), but I guess it will work fine as long as i pay attention to clock phase/polarity and the active level of "slave select" (LE pin). Are there any particular difficulties using this chip as an SPI device?

Best regards,
Torje

0 Feifei Shen over 9 years ago in reply to Torje Nikolai Thorsen

TI__Expert 3275 points

Hi Torje,

Actually it's not a standar SPI, pls refer to the datasheet for detailed timing.

Best regards,

Feifei

0 Torje Nikolai Thorsen over 9 years ago in reply to Feifei Shen

Intellectual 520 points

Feifei,

I am aware that the chip is not a standard SPI device, hence my question. Anyway, thanks for your help.

If anyone else have experience with controlling this chip by SPI, please do not hesitate to share your remarks.

Torje

0 Feifei Shen over 9 years ago in reply to Torje Nikolai Thorsen

TI__Expert 3275 points

Hi Torje,
Actually, you can use MOSI and CLK for SDI and CLK, and use IO port for OE/LE.
Best regards,Feifei

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Low-noise LED drivers and PWM