How we can charge a 5V device using a generic source of energy, monitoring the input voltage in real time

Thread Starter

andrea-poma1

Joined Dec 13, 2021
8
We have made a PCB using a MIC2876 to boost a 2.5V/4.5V 0.5 A input voltage to 5V output to be able to feed any device connected to two USB ports (USB-C and USB-A.)

We've also implemented a current sensor connected to an LED strip to monitor the incoming energy level.

We tested the unit by applying an input voltage in the range of 2.5V to 4.5V 0.5A but instead of boosting to 5V the output voltage is the same as the input - it fails its purpose.

We have tried to replace the IC and also built other PCBs but with the same result. We also tried to remove the current sensor to make sure it was not producing an excessive resistance, drawing all the incoming current but that didn't help, either.

Do you have any idea of what could cause the malfunction and do you have any suggestion to improve, if possible, the design?

Schematic-1.pngSchematic-1.png
 
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Alec_t

Joined Sep 17, 2013
12,727
Welcome to AAC!
We tested the unit by applying an input voltage in the range of 2.5V to 4.5V 0.5A but instead of boosting to 5V the output voltage is the same as the input - it fails its purpose.
Some regulators require a minimum load in order to regulate properly. What does the datasheeet for your regulator IC state? What was your test load?
 

Irving

Joined Jan 30, 2016
2,524
Simulation shows there's nothing wrong theoretically with those values. Can you post the PCB layout, both sides..
 

Thread Starter

andrea-poma1

Joined Dec 13, 2021
8
Welcome to AAC!

Some regulators require a minimum load in order to regulate properly. What does the datasheeet for your regulator IC state? What was your test load?
During the testing the input amperage range was between 0.5 to 2A, but in all case the voltage output is the same as the input
 

Thread Starter

andrea-poma1

Joined Dec 13, 2021
8
Welcome to AAC!

Some regulators require a minimum load in order to regulate properly. What does the datasheeet for your regulator IC state? What was your test load?
Hi Alec, thanks for your input, please see attached the datasheet in case you need additional information
 

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Irving

Joined Jan 30, 2016
2,524
Well I can't see anything obviously wrong with the PCB layout around the boost converter. Are you sure the extended pad under the chip is definitely soldered to AGND? Are you sure the values for R11 and R12 are the right way round (trying to set a low output voltage would have the effect you're seeing) - check the voltage at the R11/R12 junction.
 

Thread Starter

andrea-poma1

Joined Dec 13, 2021
8
Well I can't see anything obviously wrong with the PCB layout around the boost converter. Are you sure the extended pad under the chip is definitely soldered to AGND? Are you sure the values for R11 and R12 are the right way round (trying to set a low output voltage would have the effect you're seeing) - check the voltage at the R11/R12 junction.
when I don't use the variable version I remove the resistors(R11 and R12) and short outs and out, but I still have the same problem
 

Irving

Joined Jan 30, 2016
2,524
when I don't use the variable version I remove the resistors(R11 and R12) and short outs and out, but I still have the same problem
And if you scope the SW pin its static (ie no 2MHz signal)? What are EN and /PG doing? And you definitely have a good ground connection on pins 2 and 4?
 

Thread Starter

andrea-poma1

Joined Dec 13, 2021
8
And if you scope the SW pin its static (ie no 2MHz signal)? What are EN and /PG doing? And you definitely have a good ground connection on pins 2 and 4?
The voltage on the EN pin is 1.7V while on the PG the voltage is the same as at the input. As for pins 2 and 4 I checked they are connected. The only thing I haven't done yet is measure the signal with an oscilloscope or measure the frequency
 

Irving

Joined Jan 30, 2016
2,524
Hmmm, what is the value of R4? EN should be >1.5v, but how is it only 1.7v when the leakage current into EN is < 3uA and R4 is fed from at least 2.5v (therefore R4 is > 270k?)
 

BobTPH

Joined Jun 5, 2013
4,738
If that is true, EN pulled up by 10K and reading 1.7V, then I see two possibilities;

The chip is fried, or it is not connected correctly, i.e. what you think is the EN pin is not.

Bob
 

Irving

Joined Jan 30, 2016
2,524
As Bob says, something's not right there. Whats the load on the output? Can you run it with no load, or just say a 4k7 resistor?
 
Hi Irving, Hi Bob, sorry to keep you waiting but we ware running additional tests with better equipment: the result is the voltage is equal to the input and the IC does not work at 2mhz
 

Thread Starter

andrea-poma1

Joined Dec 13, 2021
8
Hi everybody,

sorry for the late response but we had a lot of trouble during testing so we have to undergo few twice with different tools.

At the end the main problem was that we took reference schematic which is for variable volatge IC, while fixed version was soldered.

Some of you spot the problem immediately but when we undergo troubleshooting purchasing a variable IC version and soldering on the board the issue remain (probably because our tool could not control the heat used during the soldering process)
My mistake was also not providing this forum with the BOM list, it will probably lead immediatly to the real problem and make it unquestionable.

Now we are going to change the configuration to support the fixed version and also we will place the input capacitors closer to the IC to reduce the noise.

My apologies again for the time you loose and my compliment for your efficiency in spotting the root cause almost at once.

My regards
Andrea Poma
 
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