TLC5947 Single Shot

Hello Martin,

Sorry, but I do not understand what you mean with single shot mode. Could you please explain in a little more detail what you want to achieve?

TLC5947 just turns on the outputs based on the data in the GS latch. So after BLANK goes low at the fifth internal oscillator rising edge, all outputs turn on until the time given in the GS latch has passed and then this specific output turns off. So if you wait until all LEDs are off and then set BLANK high, the outputs will stay off.

Best regards,
Brigitte

But how would you know they're off, I think he's asking. The internal PWM clock or a cycle auto repeat signal are not available on the TLC5947. This type of application would probably work best with the TLC5940, since the user has full control over the grayscale clock on that chip.

Hello,

i mean that the ic makes one Full PWM cycle and than stops. I multiplex the PWM and if it makes more than one i have ugly effects. I give the IC the data, it makes one cycle and than stops. The internal clock isn't led out. So i can't guess when i send the data for the next row.

Do you mean, that i must check the LED Output ? This may be a difficult problem, i must check the current or have a diode on every port. Is'nt there a better solution ?

Regards Martin

Hello,

Yes but the TLC5940 has only 16 output channels. I wanna have a simpel Driver with 24 outputs and a single shot mode ;) Is there an alternative ?

Regards M.Hermsen

Hello Martin,

Sorry, but with TLC5947 you do not have the possibility to know when the signal is shown once without observing the outputs. The internal oscillator is not given and has some variation. You might have a look on TLC5951 which gives you full control over the GS clock.

Best regards,
Brigitte

Hello,

has the TLC5952 such a function ? I saw that there are some control registers.

Regards M.Hermsen

Hello Martin,

My expectation is that you want to have full brightness control of every output in every cycle. TLC5952 has 3 brightness control registers, each responsible for 8 outputs and then with the data written to the part you can decide which output is on and which one is off. Therefore you cannot control the brightness of every output individually.

If you need to control each output current individually in every cycle and you want to have 24 outputs on one IC, then I do not see another part than TLC5951.

Another possibility would be TLC5971 which is a 12 output driver. If you use 2 in series, you can control each output individually and each group of 4 outputs additionally.

Best regards,
Brigitte

Hello,

I only want to have control over the clock, after one pwm cycle it should be stop. Or which may be the best solution, that the blank signal stops the output after a full cycle and not imidiately. The brightness is not such a big Problem, the current of each channel can be fix.

I will read the Datasheet of the TLC5952, but the timming diagramms are not quite good. Is there other Documentation for the ICs ? There are only examples and some comments, but not every detail is explanied.

I actually have build a prototype with the TLC5947, i will test some special conditions, but my Controller is on his load maximum, because i have 192 channels output and 60hz refresh. This is the reason for my wish of a simple driver with not to mutsh information on the SPI.

Regards Martin

Hello Martin,

Let me try to understand your problem to find a suitable solution:

You have 192 LEDs you want to either turn on or off in a refresh rate of 60Hz. These 192 LEDs (or channels with more than one LED) are grouped in 24 LEDs (or channels) in 8 rows. Is this right? Now you want to control 24 outputs with an LED driver and use a multiplexer to turn on one of the 8 rows.

If my assumptions above are right, please have a look on TLC5925. This part just turns on the outputs if an input is held low after clocking in the data. It is just a 16 channel part, but you can cascade several of these.

Best regards,
Brigitte

Hello,

The TLC5925 has no internal pwm. I use the IC in the following way:

- Get the PWM Values in 8 or 12bit in the IC over SPI

- Wait one PWM cycle (which is an important thing)

- then go to next row

- and so on...

So i can build an RGB Matrix with 8x8. each row has 24 channels. If i must generate the 24x 12bit pwm in my Controller this may take a much of performance.

Regards Martin