TPS61088: Chip fever

Y_U

Part Number: TPS61088

Input 3.0-3.9V and output 12V/1.5-2A ,

Question:

1: No load, the voltage is normal, but 1.0uH inductance heating, 2.2uH is better.

2: The equipment loaded with 12V/1A is restarted repeatedly after being connected to the equipment. The input is 18650 20000mA battery, and the input discharge should be enough. By the way, inductors with loaded chips are very hot.

over 6 years ago

0 Helen chen over 6 years ago

TI__Mastermind 40080 points

Dear Sir,
Do you mean the inductor is hot even at the no load condition? Did you set the TPS61088 at PWM mode condition?

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Dear Helen：

When no load, the inductance was 1.0UH before, but now 2.2UH does not heat, but the temperature is estimated at 30 degrees.I don't know if it's normal or not.

It's mainly the second question. I hope I can help you.

My schematic diagram：

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

I can't see you sch, please send the sch again!

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

Still can't see it. You can use insert file menu to try again!

0 Y_U over 6 years ago in reply to Y_U

Intellectual 270 points

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Dear Helen ：

Because the board space is limited, I use the positive and negative wiring .

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

Dear Sir,

The mode pin is connected to GND, therefore the TPS61088 works in the PWM mode. So there will be reverse current flowing through the inductor. So it will be hot even at the no load condition. a 2.2uH inductor will make the current ripple half times smaller, so it will less hot.

Since your output power very big, so please pour a big copper plane at the top layer and other layer. From your current layout, the output GND is connected with the IC's GND thermal pad through the vias. This is not good for the thermal dissipate. Please refer to the TPS61088 EVM board and the layout guide line on the datasheet for a reference.

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Dear Helen，
Is it because of heat dissipation that the chip is very hot and the conversion efficiency is low, so that when the input current is 4A (or larger), the chip current is limited and the output current is less than 1A?

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

No，it is because of the mode setting and the bad layout.

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Are there any problems with mode settings?
I'm going to draw PCB according to EVM board. Then the mode also uses PWM mode. OK?
What is your suggestion?

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

Suggest you add a zero resistor from Mode to GND. Then you can let TPS61088 work at any mode.

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Okay, I've rearranged it according to your suggestion. I'd like to ask why the input voltage of the previous design is 3.5V and the input current is less than 4A~5A. Is that the reason for the layout? Or is the chip too hot to limit the input current?

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

Dear Sir,

The input current is based on your output power Iin=Po/Vin/eff. What is the output power when you get this 4-5A input current?

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

The output power is about 12W (12V/1A)。

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

If Vin=3.3V, then Iin=12/3.3/0.89=4.08A.

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Under what circumstances, input current limiting 4A?

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

It based on the inductor your chosen. if the inductance is small, then the ripple current is very big, ILpeak=Iin+Iripple/2. if ILpeak reaches the limit point Ilim, then ILpeak and the Iin will be limited. What is the current limit resistor in your design?

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

My inductance is 2.2uH and the current limiting resistance is 100K.

It is possible that ILpeak has reached the input current limit. Whether Iripple can be reduced by increasing inductance value, but whether increasing inductance will bring other problems. What other ways to reduce Iripple?

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

When set Rlim=100k, generally Ipeak can reach 10A. Did you test the inductor current? or have you use a right inductor, did you check its saturation current?

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

I used a saturated inductance current of 13A. I did not test the inductance current when I was working.

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

Please test the inductor current, and if possible, please also test the on board Vin voltage, if there's a long cable, the real on board Vin voltage will be very low.

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Okay, I'm going to test with the changed circuit board. It's estimated that tomorrow will be the day to test what's going on. Contact you if you have any questions. Thank you very much for your support

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

Thanks for the update, good luck!

0 Y_U over 6 years ago in reply to Helen chen

Intellectual 270 points

Dear Helen，

My new version has arrived, input 3.35V/2.2A under test, output 11.89V/0.55A. The calculated efficiency is 88.7%. Previously, only 70% of the efficiency was low, resulting in large input current. Battery discharge current would reduce the voltage, so that the input voltage would drop below 2.7, so the chip could not work.

Now there is another problem. When I input high current, the inductance temperature of 2.2uH I use can reach 60 and the chip temperature can reach 55. Does this affect the use of chips and inductors? Or can you change a larger inductance to lower the temperature?

0 Helen chen over 6 years ago in reply to Y_U

TI__Mastermind 40080 points

Dear Sir,
The chip temperature can reach 75C and the inductor temp can reach even 100C, so it is OK!

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TPS61088: Chip fever