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TLC59711 board & max pwm frequency?
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TLC59711 board & max pwm frequency?

by crito on Sat Mar 29, 2014 1:25 pm

hi,

what is the pwm frequency of the TLC59711 board?
http://www.exp-tech.de/Shields/LED-Cont ... 59711.html

point is i would like to connect an arduino uno to the TLC board and connect its pwm outputs to 8 Motien led drivers to control 8 different high power leds (500mA)
Noice on the leds is an issue so i need a high pwm freqency.

i used pwm output 6 of the UNO and set it to max but that 62,5KHz is still way to low, somewhere in the MHz would be nice.
for pdf on motien see:
http://www.stadiumpower.co.uk/media/186 ... 30-600.pdf

Other reasons for using that board would be the many pwm outputs & 12 bit resolution.

thanks

crito
 
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Re: TLC59711 board & max pwm frequency?

by adafruit_support_rick on Sat Mar 29, 2014 2:09 pm

I believe the internal PWM reference clock is 10MHz.

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Re: TLC59711 board & max pwm frequency?

by crito on Sun Mar 30, 2014 5:40 am

hi,

>I believe the internal PWM reference clock is 10MHz.
i can see on the specs of the TLC59711 that the i2c transfer rate is (max) 10MHz but i can't find the pwm frequency.

http://www.ti.com/lit/ds/sbvs181/sbvs181.pdf

Can you let me know where that is mentioned?

Also with 12 bit you have 4096 steps, am i reading it correct that when you have the 10Mhz clock (0,1us) one period of the PWM is 4096 x 0,1us so 409,6us?
So basically not 10Mhz but 10Mhz/4096 = 2441Hz (2,4Khz)

crito
 
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Re: TLC59711 board & max pwm frequency?

by adafruit_support_bill on Sun Mar 30, 2014 6:09 am

The internal oscillator frequency 'Fosc' is 10 MHz. This is divided down by 2^16 to get 16 bit resolution on the PWM period. This gives you a PWM update frequency of ~153Hz.

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Re: TLC59711 board & max pwm frequency?

by crito on Sun Mar 30, 2014 6:53 am

thanks,

>This gives you a PWM update frequency of ~153Hz.
ok, so if i look at the pwm signal with a scope i get a 153Hz pwm signal correct? (or with update frequency do you mean a change from 1 pwm setting to the next in case you change the duty cycle?)

a 153Hz pwm signal is to low for the application i have in mind.

What do you recomend to change the pwm to analog
or does adafruit have dac boards?

crito
 
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Re: TLC59711 board & max pwm frequency?

by adafruit_support_bill on Sun Mar 30, 2014 7:23 am

if i look at the pwm signal with a scope i get a 153Hz pwm signal correct?

I believe that is what you would see. Fromthe data sheet, it looke like the internal oscillator provides a 10MHz time base which is divided down into 2^16 increments. The 16 bit PWM setting determines how many of those increments are in the ON state to set the duty cycle.
does adafruit have dac boards?

We have a 12-bit DAC breakout: http://www.adafruit.com/products/935

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