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Problem with 2.8 -> 5V power supply

jozef007

Nov 9, 2019
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Hi,
I having problem with power supply, which for inputs from 1.8 - 2.8 V should generate 5V on outputs.
Currently I don't have load on output, I just measured voltage there, which was around 1.5V and circuit TPS61032RSAR started overheated, current on input was 440mA. I tested thoroughly all 16 pins, there was not a issue. Can some please look into, not sure, what I'm doing wrong. I attached schematic, bellow is link for IC. Thx

http://www.ti.com/lit/ds/symlink/tps61030.pdf
 

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Alec_t

Jul 7, 2015
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Welcom to EP!
Try adding a nominal load, say 1k, and measure again.
 

jozef007

Nov 9, 2019
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Welcom to EP!
Try adding a nominal load, say 1k, and measure again.
Hi Alec, I try it but result is the same. Can you please assess if my schematic has a merit? I calculated parts, want to be sure, that they are correct.
 

Alec_t

Jul 7, 2015
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Your circuit may be oscillating uncontrollably.
I don't see the 100nF decoupling cap (as recommended in the datasheet), which should be directly across the supply pins of the IC.
Does your circuit layout follow the datasheet (section 13) recommendations? Hopefully the circuit isn't on a breadboard!
 

jozef007

Nov 9, 2019
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Your circuit may be oscillating uncontrollably.
I don't see the 100nF decoupling cap (as recommended in the datasheet), which should be directly across the supply pins of the IC.
Does your circuit layout follow the datasheet (section 13) recommendations? Hopefully the circuit isn't on a breadboard!
I used SMD's so whole board was designed, hopefully we are talking about same stuff but I have 10uF as C2 for such function (as per TI documentation Fig. 19).
Here is PCB footprint (C2=C32, R3=R22, R7=R25,C9=C5,C23=C3)). C2 is on input. Maybe something I'm missing here? Thx
upload_2019-11-10_20-35-28.png
 

bertus

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Nov 8, 2019
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Hello,

In the layout in the datasheet there are not such small traces.
They use complete planes for the connections.
They also show where vias are planned:

tps6103X layout.png

Bertus
 

jozef007

Nov 9, 2019
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Hello,

In the layout in the datasheet there are not such small traces.
They use complete planes for the connections.
They also show where vias are planned:

View attachment 46387

Bertus

Thank you for guidelines, but is such change, via way how I did PCB, effect so much function? I don't have so much knowledge to explain it...
 

Hunter64

Nov 20, 2018
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Nov 20, 2018
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"As for all switching power supplies, the layout is an important step in the design, especially at high peak currents and high switching frequencies. If the layout is not carefully done, the regulator could show stability problems as well as EMI problems."

Just a quote from the datasheet mentioned in the first post.
 

jozef007

Nov 9, 2019
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"As for all switching power supplies, the layout is an important step in the design, especially at high peak currents and high switching frequencies. If the layout is not carefully done, the regulator could show stability problems as well as EMI problems."

Just a quote from the datasheet mentioned in the first post.
Word is around, that I need to pay more attention to the documentation... Must admit, they are some improvements need to be done :)
Let's assume that I will follow PCB footprint to the letter, otherwise there is not visible issue in schematic itself? Just reminding that I will have input 1.8-2.8 V and output 5V with expecting load max 1.5V. Thx
 

jozef007

Nov 9, 2019
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I get verified that schematic is correct. I will create new PCB layout and hopefully will work. Thx for assistance. I'm concluding problem as resolved.
 
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