LED1202: LED channel damage

[SunilHD]

Hi Team,

We have used LED1202 in our board where one LED driver is connected to Microprocessor and one LED driver is connected to MCU.
We are seeing random LED channel damages (with LED driver which is connected to MCU) while device is in running state, and LED channel damage issue is random that any or all channels get damage which are connected to LEDs only. LED turns ON permanent which channel got damaged.

We had debugged the operating voltage fluctuations, ground bounce effects but nothing happens during the LED channel failure.

We have limited LED channel current to 6mA and using LED function as ON and OFF only. No PWM functionality os being used here.

Could you please let us know what can be the root cause here behind LED channel damage?

Thank you

[AScha.3]

Hi,

Can you show the circuit, so less guessing game?

[SunilHD]

Hi,
Please find the below circuit.

 

[AScha.3]

Hi,

Your circuit doesn't show the connection to the LED and what kind of LEDs used.

But from your findings with constant on driven LEDs: looks like the driver was overloaded, too high current or induction of a spike .

Which kind of LEDs, forward voltage?

And line/wire length from driver to GND return, = loop length: driver -- led-- gnd at driver?

I would at first increase the 100 resistors, maybe 330 ohms, to be sure, no over current can happen.

[SunilHD]

Hi,

LEDs are on Membrane keypad so it's not in the schematic design. We are connecting keypad to connector. On keypad, LED Anode is connected to +3.3V and Cathode is connected to LED driver IC pin through 100Ohm resistor.

We have set 100% PWM and 6.7mA current limit on each LED Driver channel using internal registers. Do you still suggest to increase series resistor to >100Ohm value?

Thank you