next topic »

[on:]

Hello, everyone. I'm building an 8x8x8 cube and have eight TLC5951s and a handful of a P-channel Power MOSFET found at http://www.ti.com/product/csd25401q3. I'm pretty new to embedded electronics, and - specifically - transistors, so I was wondering how I could use the driver and transistor in combination to be able to mux one horizontal plane at a time. All of the RGB LEDs in one horizontal plane share an anode. My µC runs off of 3.3V and defaults to an internal pull-up. Thanks!

[Reply #1 on:]

http://www.ti.com/lit/ds/symlink/tlc5951.pdf

Each TLC device will control a row of LEDs. Eight devices will control 8 rows, that's 1 layer. All the anodes from 1 layer will have current sourced from 1 PNP, or P-channel, device.
All the LEDs in a column get their cathodes connected in parallel, to a single TLC pin.
Send out TLC data for 1 layer, enable that layer's current source.
Repeat the next layer.

[Reply #2 on:]

http://www.ti.com/lit/ds/symlink/tlc5951.pdf

Each TLC device will control a row of LEDs. Eight devices will control 8 rows, that's 1 layer. All the anodes from 1 layer will have current sourced from 1 PNP, or P-channel, device.
All the LEDs in a column get their cathodes connected in parallel, to a single TLC pin.
Send out TLC data for 1 layer, enable that layer's current source.
Repeat the next layer.

Thanks. Having the drain connected to 3.3V, source to the TLC5951 pin, and switching the gate between GND and 3.3V has no effect (LED is always on).

[Reply #3 on:]

Source goes to the RGB LED anodes. LED cathodes go to the TLC pins.
What you are doing is selecting which set of LEDs are having current sunk thru them by the TLC.

[Reply #4 on:]

Source goes to the RGB LED anodes. LED cathodes go to the TLC pins.
What you are doing is selecting which set of LEDs are having current sunk thru them by the TLC.

Sorry... that's what I meant. What you described is my configuration. Switching the gate between GND and 3.3V does not change the state of a test LED. Any tips?

[Reply #5 on:]

You are sure its a common anode LED?
LEDs might also have higher Vf, need more than 3.3V to turn on.
Got a part number?

[Reply #6 on:]

Hm... I doubt that's the issue; like I said, it's always on.

[Reply #7 on:]

VGS = –2.5V 13.5 mΩ
VGS = –4.5V 8.8 mΩ

At 3.3V it should switch on/off okay.

Can you post a pic of your setup?