I have integrated the TLC5973 into a design, a section of the schematic is shown below:
There are 11 of these ICs in a chain.
When I attempt to program the devices, the data successfully cascades through the chain of devices, and a GSLAT sequence will allow the first device in the chain to be programed again:
However, no output is observed from the LEDs connected to the chips.
Here's a closer view of the signal sent to the first chip:
What reasons could cause this strange behavior?
Hi Jared,
Please find attached an annotated version of the last image in my post, showing that the write command is 3AA, and the data is {000, FFF, FFF}.
Thanks.
Hi Jared,
Here's an oscilloscope capture of the device's OUT0 (yellow) after transmitting RGB={7FF, 7FF, 7FF} (in blue).
The voltage is ~8V, which is the 12V Vled - the 3x Vf of the LEDs.
There is some light switching noise at ~1kHz as shown here, noting the cursor position and 1/dx in the panel on the top left:
However, this doesn't resemble the expected PWM output pulling the LEDs to ground.
Hi HB，
1. Please help to check the timing requirement of TLC5973.
2. If the signal is nothing wrong and the power supply is fine too. Please help to check if there is any problem with the IC welding.
BR, Jared
The image below shows a transmission of a "0", with a pulse width of 160ns (OK), and period of 6.2us. This gives an fclk of ~160kHz (OK).
The EOS hold time is 24us. 22us < 24us < 35us -- OK
The GSLAT time is 60us. 50us < 60us -- OK
The soldering is of good quality.
