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TPS63020 getting hot when switch on， even thought there is not load

Kevin Xiao

Prodigy 175 points

Other Parts Discussed in Thread: TPS63020

HI,

I have done a PCB with a TPS63020 who delivers 5.5v under Vin=3V-5.3V.

There are two question that i found when i test my PCB,

1, when the input voltage is high than 4.7V, the TPS63020 close, and not voltage is delivered.

2, when the input voltage is lower than 4.7V, for example, 4.5v, the chip can deliver 5.5v, but the input current to the chip is above 1.5A even thought there is no load. At first, it can deliver stable 5.5v, but the chip is getting hot and hot, and for about 1 or 2s, the output voltage start to oscilation.

The voltage of the pin is show below.

Wish for reply.

over 9 years ago

0 Florian Feckl over 9 years ago

TI__Expert 7110 points

Let me place a comment on the schematic first: please decrease your feedback resistors by two. A higher upper resistor than 1MOhm can cause Noise problems.

Does the waveforms show the output voltage? What is the timebase?

Is there any operation point (VIN) where the device behaves as it should and the input current less than 5mA (as the device is forced into PWM operation)?
Is the load the diode from the schematic?

0 Kevin Xiao over 9 years ago in reply to Florian Feckl

Prodigy 175 points

HI,

Sorry for reply you for so long time.

Firstly, i change the feedback resistors to 500K and 60k, which are the resistors i have in hand, but it seems making no effect.

I have capture some waveforms about the input voltage and output voltage, so you can know the real situation.

The output load is just the diode, but when i remove the diode, the input current is still very large.

Next, I will show some waveforms with the condition below.

VIN(set)=4.5V

Vout(set)=4.65V

Channel1: VIN

Channel2: Vout

1. The total waveforms.

2. The 10 Period waveforms, which change with time.

3. The two period waveforms, which change with time.

That is my real situation.

Wish for you reply.

0 JohnTucker over 9 years ago in reply to Kevin Xiao

TI__Guru**** 191445 points

What is the cathode of the LED connected to?

0 Kevin Xiao over 9 years ago in reply to JohnTucker

Prodigy 175 points

HI,

the cathode of the led is connect to GND.

I'm sorry that i didn't capture the total picture which make you confuse.

Thanks for you reply.

0 Kevin Xiao over 9 years ago in reply to JohnTucker

Prodigy 175 points

It first connect to resistor, then to the GND.

0 Florian Feckl over 9 years ago in reply to Kevin Xiao

TI__Expert 7110 points

How does TPS63020 behave once you do not use the LED as a load? Do you see a strange behavior if you just use a resistive load?

0 Kevin Xiao over 9 years ago in reply to Florian Feckl

Prodigy 175 points

I remove the LED, but it behave the same.
it is also the same when i apply the resistive load.