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Original question:

BQ51051B: No voltage output when connected with Qi charger

BQ51051B: Low voltage output when connected to Qi charger.

Marcus Toivonen
Prodigy 20 points
Part Number: BQ51051B

Hi, 

Regarding my previous issue with the BQ51051B, I have been trying to get it working off and during the last months.

I am still unable to get a real output from the chip.
I used the 19mm coil as suggested and changed R2 in the schematic I provided to 1.4k.
When I put the device on a Qi charger, it shows that it activates ok and I am getting a voltage output from the chip, however the output is consistently only 0.86V

When I measure from RECT pin, I am getting a fluctuating voltage of 3.3 - 3.6V.

When I test without a battery connected, should I be getting the full charge voltage?
Even if I test with a battery connected, I see no difference in voltage when the charger is activated.

I have multiple devices and they all operate identically.

I am sure that I am missing something very simple.
Based on this information, can someone recognise what could be the problem here?

Thank you!

  • 0
    Prodigy 20 points

    It seems I have found the issue. I will write the solution here if someone else later has this problem. Resistor R5 between FOD and RECT. I have it originally at 393R, I increased it to 40kR and the charging started to work immediately, now the output goes strong up to 4.02V and charges the batteries ok. I consider this issue solved.