TLC5955: Some Issue of TLC59555

Dear Sir/Ms.
Additional information from customer.
1. The temperature of the first one will be higher than the latter. Will this be the case with actual use?
1 & 2 temperatures > 3 & 4 about 15 ° C, 3 & 4 > 5 about 10 ° C, the first temperature is about 80 ° C
Test RA conditions 60 ° C 90% about 4 hr. LED ON/OFF will be disabled (always ON)
2. The last TLC5955 is not full, but the last TLC555 channel is broken down (low impedance). Have you seen this situation? How to design the channel that is not used?
The last one is not full, but the breakdown will happen in every channel.
Condition description: At the beginning of the test, all ok, but after a few times, there will be several LEDs that will not go out. The measurement problem position LED A to ground impedance (K connected IC channel) will be 1~2MΩ. (Normal condition meter display open)
Confirm the OK light board, and repeatedly test the LED Turn on, it will produce the LED does not go out.
Lighting conditions: VCC 3.3V/VLED 6V/ILED Set 20mA/ 5 series in series, use 216 channel, 1channel to drive 1 LED.
3. Throw into the ring temperature furnace. When the IC temperature is greater than 85 degrees C, abnormal operation will occur (for example: the current of each channel cannot be turned off, and the output is always 20mA). The restart is also the same. The entire board must be taken out and cooled down before it will return to normal again. Is this situation normal?
4. If the LED Vf=3V, what is the VLED voltage I need?
At present, the channel needs to be set to 20mA due to the demand. The actual VLED=6V~~ is designed. Is there any problem with the design? How to calculate the peripheral circuit?
This customer is very good. If you still want more information to judge, please let me know, I can ask the customer.
Best Regards,
Kami Huang

1. It's quite strange. Can you share the schematic?
2. The unused channels can be left floating.
3. VLED = VF+Vth, Vth is the minimum voltage to get the constant current. And you can get the data in figure 1/2/3. For 20mA, 0.5V is enough, so VLED=3V+0.5V=3.5V. 6V is too high and it will have ~2.5V drop on the chip. If all 48 channels are turned on, the power dissapation is around 48*20mA*2.5V=2.4W, which is quite high.

Hello Kenneth,
1. It's quite strange. Can you share the schematic?
A: I got schematic, May I have your email ? I can email schematic to you.
2. The unused channels can be left floating.
A: keep floating
3. VLED = VF+Vth, Vth is the minimum voltage to get the constant current. And you can get the data in figure 1/2/3. For 20mA, 0.5V is enough, so VLED=3V+0.5V=3.5V. 6V is too high and it will have ~2.5V drop on the chip. If all 48 channels are turned on, the power dissapation is around 48*20mA*2.5V=2.4W, which is quite high.
A: customer only obtain 1.7A when VLED=4V.
Best Regards,
Kami Huang

Hello Kenneth,
Following is new question from customer.
1、 Is Set up condition ok or not?
Current setting for TLC5955 were MC=0x05, DC=0x7F, BC=0x68.
VCC=3.3V/VLED=6V
2、 What status(condition/driver current/vled) will damage TLC5955?
3、 Do you have any recommend schematic for protect TLC5955 I/Os when unstable signal?
I think wire 10K resistor to GND. How do you think?
Best Regards,
Kami Huang

Hello Kenneth,

Can you share the schematic?

as attached file.

BL Board schematic-post.pdf

Best Regards,

Kami Huang