TPS54201: Parts blowing up

Bryan Denton

Part Number: TPS54201

I am using a TPS54201 LED driver. The driver worked fine at first. However, after the power (24V) had been cycled about 30 times, the circuit started to draw excessive current from the power supply (the power supply current limited at 1A, 0.8V). I replaced the TPS54201 and all worked fine again. However, after cycling the 24V several times, this IC became defective in the same way as the first. I then replaced the TPS54201 with a third unit. This produced the same fault the first time 24V was applied. With this IC, no signal was applied to the PWM pin and so it should not have attempted to drive the LEDs!

I suspect that the output FETs have either both gone short, or are both being turned on. Either way, there is a very low resistance path through the device.

I have attached my circuit diagram and waveforms showing the SW pin on the device. I note that the minimum voltages on this pin are:

-0.3V or -5V 20ns transient. The negative "blip" on my SW waveform is around 0.6V for 30nS!!

My LED current is 75mA

My LED voltage is 15V

Any ideas?

over 3 years ago

0 Bryan Denton over 3 years ago

Prodigy 10 points

Sorry... Here is the circuit diagram

0 Yuting Shao over 3 years ago

TI__Genius 13001 points

Hi Bryan,

Could you decrease the input voltage to 20V and try again? I suspect there is input voltage spike above 30V and make device damaged.

Robin

0 Yuting Shao over 3 years ago in reply to Bryan Denton

TI__Genius 13001 points

Change the input capacitor with larger one at the same time.

0 Bryan Denton over 3 years ago in reply to Yuting Shao

Prodigy 10 points

Many thanks for the reply..... As I read your reply, I was thinking along the same lines. The key point is that when the devices were destroyed, the 24V power was not applied by turning on the bench power supply, but by connecting the lead to the power supply. This is how the device would be operated in use! When you do this, you do indeed sometimes get a spike. This is probably made worse as there is very little current being drawn when the unit is first connected. Here are three traces. The first is with a 220uF capacitor to smooth things out. The second is with just a 10uF on the PCB. This did not blow up the device but does show overshoot. The third shows overshoot to 34V! which did indeed kill it stone dead!!

0 Yuting Shao over 3 years ago in reply to Bryan Denton

TI__Genius 13001 points

Hi Bryan,

So we find the cause is input voltage spike is too high... Is it acceptable to add large capacitor?

Robin

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TPS54201: Parts blowing up