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]

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.

• DB4897Qi-1.3 compatible wireless power receiver reference design for 2.5W wearable applications
• TN1440STDES-WLC38WA wireless power receiver quick start guide and test report
• STDES-WLC38WA GERBER
• STDES-WLC38WA BOM
• STDES-WLC38WA SCHEMATIC
• DB4944Firmware for STDES-WLC38WA and STDES-WLC38TWS wireless charger receiver evaluation kit

[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

• DB49182.5W Qi compatible wireless power transmitter reference design for wearable applications
• TN1442STDES-WBC86WTX Wireless Power Transmitter Quick Start Guide and Test Report
• STDES-WBC86WTX GERBER
• STDES-WBC86WTX BOM
• STDES-WBC86WTX SCHEMATIC
• DB5078Firmware for STDES-WBC86WTX wireless charger transmitter evaluation kit

[HiepLe]

Hi @willzhou,

Below is the scope after I modify the 2 capacitors COMA from 22nF to 47nF and 2 capacitors COMB from 10nF to 22nF, it still does not work.

What should I do next? Should I continue to increase the capacitor value?

Also, I attached the image of my wireless charger pad that I am using, this pad can charge my iPhone XS Max

Thank you

Best regards

Hiep Le

 

[willzhou]

HI

Do you have qi-sniffer, seems TX Control error timeout, just want to make sure.
Also can you use some TX what can see detail logs, for example STWBC2.
May i know what is the volume of application, and i can find local or related FAE to support you?

[HiepLe]

Hi @willzhou,

I don't have Qi-sniffer

This is the first time I have designed this STWLC38 chip and I don't have experience in this field.

My customer plans to produce 10,000 devices for this application

I am living and working in Vietnam, if you have any FAE, please help me

Or if you have any suggestions, please let me know, I will follow your guide, I need to debug and fix this issue ASAP.

Thank you so much

Best regards

Hiep Le

[willzhou]

HI 

Do you use correct fw file, please try attach file.

[HiepLe]

Hi @willzhou 

Below is my custom PCB,

How can I use these firmware files?

Does the MCU need to communicate with the STWLC38 chip to enable the chip?

I think when placing the circuit in the TX charger, it will need to power up first, then the MCU can communicate and configure the STWLC38 chip. According to the current status, the STWLC38 chip has not been powered-up yet, so how can we use firmware to communicate with the STWLC38 chip?

[willzhou]

Hi
Please follow this link, it have the answers.
https://community.st.com/t5/power-management/wireless-charging-solution-wiki/td-p/684177