TLC5930: or alternative PWM - Constant Current driver with very high Internal Oscillator for the PWM-Frequency

Stefan Krueger

Part Number: TLC5930
Other Parts Discussed in Thread: TLC5947, TLC5971

Hello Community,
Hello TI-Team,

I am on the search for an Constant-Current LED-Driver for an Persistence Of Vision setup.
the spinning-disk type... similar to the classic Propeller-Clocks...
for this my main requirements are:

multiple RGB LEDs per driver (>= 4Leds per driver)
target Channel Current 20..40mA
PWM frequency >= 10MHz
PWM resolution >= 10Bit
internal oscillator
serial data in out - spi compatible (Data / clock)
only to signals (if possible - they need to get to the rotating part... so less signals is better..)

i found the TLC59730 and if i understand the Datasheet correct this should fill most of the points.
- have to check what signals are minimal possible...
*PRINCIPLES OF OPERATION* page23 section 'DSG function (dual source gray scale clock)' mentions that the internal generated clock is maximum of 10MHz - i think for my target of 10Bit PWM resolution this is the lowest possible value...
(i calculated this with my outer circumfance and how fine i want to have the 'virtual pixel spacing')
if someone is interested in the fine details of my calculations - the project is open source and documented at github: https://s-light.github.io/ortogere/ideas/POV/ (the link points to the calculations table - my target pixel pitch is 1mm)

if you know other drivers that fit my needs pleas let me know!
the tlc5930 is really expencive and i found no arduino or similar code examples out there for a 'quick-test'...

sunny greetings
stefan

over 6 years ago

0 Rosley Ge over 6 years ago

TI__Intellectual 950 points

Hi Stefan,
I suggest TLC5947 to you. 24CH LED driver with internal oscillator.
Please check the datasheet in Ti.com.
Thanks,
BRs,
Rosley

0 Stefan Krueger over 6 years ago in reply to Rosley Ge

Intellectual 670 points

Hi Rosley,

thanks for your reply.
i had a look at the TLC5947.
i think the pwm is to slow for me - its only 4MHz -
so this means 250ns shortest on-time. and thats to long.
my current maximal on duration per pixel is targeted at 122426ns (122us)
here is my quick overview for the resulting bit-on-times:

bit depth	bit duration	bit update rate
8bit	478ns	~2.1MHz
10bit	120ns	~8.3MHz
12bit	30ns	~33MHz
16bit	1.8ns	~534MHz

with this table i have quickly found that 16bit is no way to go ;-)
(the leds are not quick enough for this i think...)
and i originally hoped i could increase my overall update-rate to 60 updates/second.
that would mean the timings here get half..

that is the reason i have written the 10bit resolution and PWM frequency of >= 10MHz ;-)

are there some other drivers in the TI portfolio that fit this?

sunny greetings
stefan

0 Stefan Krueger over 6 years ago in reply to Rosley Ge

Intellectual 670 points

Hi Rosley,
please see my second post / answer.
if you already get the information that i have posted more information ignore this here - i just tried the 'react Answer' button i got per mail...
sunny greetings
stefan

0 Kenneth Du over 6 years ago in reply to Stefan Krueger

TI__Genius 14295 points

Hi, Stefan,

Another device with internal oscillator is TLC5971, and frequency is 10MHz.

Please take a look.

Thanks.
Regards,
Kenneth

0 Stefan Krueger over 6 years ago in reply to Kenneth Du

Intellectual 670 points

Hi Kenneth,

Thanks for the suggestion.
i have used the TLC5971 in an other project and its a really nice chip!
the 10MHz (bit-time=100ns) would fit. is it possible to reduce the pwm-resolution on this to 10bit?
otherwise with 16bit it takes to long for full brightness
65525*100ns = 6,55 ms
and as i wrote in the table above i have only 0.122ms maximum duration for full on.

are there other 10bit or 12bit drivers with external clock?
i find it hard to sort the product-overview table and know which are 8bit or 10bit or 12bit...
on my search i found two other chips that eventually could be interesting - for better structure opened related questions for both:

I am looking forward to learn more about the differences of the multitude of drivers ;-)

sunny greetings
stefan

0 Kenneth Du over 6 years ago in reply to Stefan Krueger

TI__Genius 14295 points

Hi, Stefan,

It's unable to reduce the PWM to 10 bits.

I answer you questions for another two threads.

Please let know if you still have questions.

Thanks.
Regards,
Kenneth

0 Stefan Krueger over 6 years ago in reply to Kenneth Du

Intellectual 670 points

Hi Kenneth,

thanks for your time and the answers.
i think for now this is solved.
if i have more questions i will let you know.

sunny greetings
stefan

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

Power management

Power management forum

TLC5930: or alternative PWM - Constant Current driver with very high Internal Oscillator for the PWM-Frequency