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LED Drivers/LCD Bias
LED Drivers/LCD Bias Forum
TLC5947 not working
I'm using the driver to control only one LED in each output.
The voltage applied to the driver and LEDs is 5V, the chip package is HTSSOP and the resistor Riref is 2.2k
Since I'm working with a prototype, I soldered the device with a regular solder iron and used silicone grease to try to improve the thermal characteristics because I couldn't solder the thermal pad to the board.
When the circuit is turned on, all the LEDs flash once for less than a second and that is all I get. No matter how slow I send the information to the driver, nothing happens, the LEDs remain off. I don't even get random brigthness at power up with Blank low.
Does the thermal pad must be connected to ground for the device to work properly?
Thanks in advance
For the TLC5947, the power pad should be connected to ground. It can be left floating, but this probably isn't the best option thermally. Even if you connect the power pad to ground, please be aware that the IC ground pin should be used for all ground connections and return paths. You can route ground signals to the power pad as long as the power pad is directly connected to the IC ground pins. Note that althought the datasheet says the PowerPad is not connected to ground, what it really means is that the PowerPad is not intended to be a ground connection. The PowerPad is connected to the IC's substrate (ground) through a thermally conductive epoxy that may have either good or bad electrical performance. You should NOT expect current to flow into the IC through the PowerPad. You must design the PWB to make sure the currents in the PWB can reach the IC ground pins.
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