STWLC38JRM does not output 5V at VOUT pin

[HiepLe]

Hi all,

I am designing the custom wireless charging receiver using the STWLC38JRM chip

Currently, when I put the circuit on the wireless charging pad (Qi standard), I notice that the STWLC38JRM chip does not output 5V at the VOUT pin. 

Below is the schematic, I copied all the things from the STDES-WLC38WA board, the coil part number is 760308101219 but the circuit does not work, the only thing that worked is the I2C communication, when I supply 5V to the VOUT pin, I was able to communicate and read ID chip.

and Below the schematic is the scope that I captured when put the circuit on the wireless charger pad

Red is AC1, green is AC2, yellow is VRECT, and blue is VOUT

I see the VOUT is still 0V and the AC1, AC2, and VRECT waveforms look like wrong.

Currently, I don't use the temperature sensor NTC so I designed a 100k resistor pull-down and 100k pull-up to VAA at NTC (F1 pin).

Can you guys help me fix this issue?

Thank you so much

 

[willzhou · Accepted solution]

Hi Sir
May i ask what is the application?
seems you follow our STDES-WLC38WA design. Please follow below link:

coil 760308101219 is 11.8 uh, based on https://www.we-online.com/components/products/datasheet/760308101219.pdf.
From your sch C tank is 247nF, seem right

From your waveform, Vrect send some ASK packet and then drop power, seems TX CEP timeout.

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[HiepLe]

Hi @willzhou,

My application is a small wearable device

I copied all the schematics of the STDES-WLC38WA design, but my circuit does not work.

I think the schematic is correct.

I tried with another wireless charger pad but it still did not work.

With the above waveforms, what should I do next?

Thank you

[willzhou]

HI 

STDES-WLC38WA design work with STDES-WBC86WTX, and coils is smaller.

But you use TX with standard coils, 

I suggest you modify COMA/COMB Cap value, make it larger, currently your sch COMA Cap 22nF and COMB Cap 10nF, suggest to modify to COMA Cap 47nF and COMB Cap 22nF

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