TLC5946: Can I cascade a TLC5946 with a TLC5941?

Hi Zhonghui,

Yes theoretically it can work. I am curious why customer want to mixed use TLC5941 and TLC5946?

Hi Wu,

Thank you for your response! Okay, good to know. I have been looking at more of the TLC594x's and noticed the TLC5947 and the TLC5944.

For some background:

I have 24 different LEDs (5 red, 5 blue, 5 green, 4 white, 5 orange) that need between 8-20mA, depending on the LED colour. I would like to use the 24 channel, 30mA TLC5947 to power them and use PWM to change the current as it turns on different coloured LEDs. Each colour of LED is turned on at a different time (ie. all red on, then off, then all green on, then off, etc.) so I can use PWM to change the output current for the LEDs that are on at a specific time.

I also have 5 UV LEDs that need 55mA of current. I would like to use the 60mA TLC5944 to power those.

I only have one raspberry pi to power these, so I am wondering if I can cascade the two drivers (5946 and 5944) and use PWM to turn them on for specific currents?

In addition to my response: do the TLC5947 and the TLC5944 have the same communication protocols? So I can cascade them with the same connections and treat them as the same devices (just numbering the outputs differently (ie. 0-23, 24-40) in my code)?

Thanks 

Best regards,

Hi Zhonghui,

I think TLC5946 and TLC5944 could be cascade in one series, and the control method are also the same. Some details with XHALF pin of TLC5946 is different. But I did not try it before, only can say theoretically it can work.

Here I have another solution recommend is LP5036, which is a 36 channels device with 35mA for each channel. Paralleling 2 devices could get 70mA current capability. So for customer's application which need 24 channel for optical light LEDs and 5 * 2 channels for UV LEDs

Hi Wu,

Thank you for the insight! We unfortunately cannot go with the LP5036 because it is not of high enough accuracy and the dimming controls 3 outputs at a time. Thanks for the suggestion though.

Do the TLC5947 and the TLC 5944 have the same control mechanism? Could we use the same code to run them? And can we cascade them?

I was also wondering if it is possible to do parallel outputs on the 5947 to double the current output? What would that look like?

Best regards,

Hi Wu,

Is there any update?

Thanks.

Best regards,

Hi Wu,

 After doing some designing today, I have two questions:
(1) Can you combine outputs to a single LED on the 5947? Ie. Can I use two 5947's to power one LED so I get 2*30mA output? Can you show me a schematic of what it looks like?
(2) Can you double the output for a 5946? (same as questions 1)
(3) Can you cascade the 5947 and the 5946?
Thank you for all of your help.

Best regards,

Hi Zhonghui,

LP5036 can separately control all output individually, by the color registers, while the brightness registers adjust 3 outputs at a time.

For TLC5947, the data format is different with TLC5944 and TLC5946. TLC5947 have 24 outputs and needs 12 x 24 bits totally. Also it do not have DC function.

The outputs of all TLC devices are current sinks. So you could combine 2 channels together to get a higher current capability. Just connecting the 2 outputs pins together and to the cathode of LED.

I think it is OK to cascade TLC5947 and TLC5946, since they are both shift register inside. But it would be much complex since their control method is much different. TLC5946 need to set DC value firstly and additional GSCLK.