EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: HermesTheNurse on August 19, 2024, 06:55:53 am
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I apologize in advance if I violate any forum conventions here. If that happens I will adapt postings accordingly moving forward.
Context:
I have been working on a PCB design that incorporates the TPS61090 (Boost converter) and MCP73871 (Charge controller) of Adafruit's Powerboost1000C, as seen here: https://learn.adafruit.com/adafruit-powerboost-1000c-load-share-usb-charge-boost/downloads (https://learn.adafruit.com/adafruit-powerboost-1000c-load-share-usb-charge-boost/downloads).
I've checked the Powerboost1000C circuit diagrams and Eagle PCB board files provided by Adafruit, and pretty meticulously matched everything to spec. However, when I plug this in, the boost converter chip (TPS61090) gets extremely hot, and yes, eventually starts smoking.
Circuit:
For power, I will be switching between a +5V USB and a 3.7V-4.2V Lipo battery supply. The power circuit is the portion highlighted in Yellow, where the microUSB port feeds USB power from the Teensy's VUSB pin (#1) to a MCP73871 charge controller (U2, #2). Directly below this are two terminals (Orange) where the battery joins the circuit. Both power sources then feed into the TPS61090RSAR boost converter (U1, #3). If the battery is discharging, the 3.7V-4.2V will be stepped up to +5V here. Finally, power is delivered back into the Teensy through the +5V "VIN" pin (#4).
(https://i.imgur.com/vsIhJzV.png)
TPS61090 (Boost Converter):
(https://i.imgur.com/qaaecZ6.png)
MCP73871 (Charge Controller):
(https://i.imgur.com/9HJ9vZ7.png)
Physical Board:
(https://i.imgur.com/JV38XMT.png)
Additional Project Files:
Here https://github.com/ColbyDAllen/Wearable-Drum-Machine/tree/main/Version%201/Hardware/E-CAD/Gerber_Drill (https://github.com/ColbyDAllen/Wearable-Drum-Machine/tree/main/Version%201/Hardware/E-CAD/Gerber_Drill) are the Gerber/Drill files that I used to have this board fabricated.
Here https://drive.google.com/file/d/1sePkgNdDCUta4Hd3auVm2ioGn66iGeJi/view (https://drive.google.com/file/d/1sePkgNdDCUta4Hd3auVm2ioGn66iGeJi/view) is the full schematic of the board. For some reason, the resolution when zooming is much better on the mobile app (You can even read the text on the datasheet pinouts).
2 Questions:
Having read elsewhere that the passives (Capacitors, resistors, etc.) might need to be placed closer to their respective ICs, I have two questions:
1. Could I be missing decoupling capacitors; 10 or 100nF caps, placed close to all power inputs?
2. I'm thinking a board revision is the best plan of action moving forward. Are there any steps that I might want to take before that?
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For a boost converter it's the output capacitor that is critical. Your layout is reasonable (C5 is close, C4 could be closer), but your routing may need improvement. Try to put the output capacitor loop (pin1,15,16 -> C4 -> pin5,6,7) in single layer with nice wide trace/polygon. Or at least put more than one via if you have to change layers.
As for your design, I don't see anything wrong with the circuit. Are you sure there weren't any solder bridges underneath the IC? You got enough caps already, and bad layout alone rarely result in such catastrophic failure.
Finally, power is delivered back into the Teensy through the +5V "VIN" pin (#4).
You did cut the VUSB-VIN jumper tie on the teensy right?