BQ51003: Transmit side overheating

May

Part Number: BQ51003

Hi,

Customer have issue with the IC, please see details below.

"We're having issues with our transmit side overheating when the BQ51003 is under light load (1-20mA). Looking at the specificaiton, I see with the dynamic rectifier control / efficiency scaling that the performance is pretty poor at light load. Is this part meant to operate under light load and if so, how to configure it? Also, is there a recommended TI transmitter part that works well with the BQ51003? Our application could potentially draw very little current, so we're worried about overheating"

Regards,
Maynard

over 2 years ago

0 Bill Johns over 2 years ago

TI__Guru 65866 points

Hi Maynard

Send schematic for review also coil that is used.

0 Matt Staniszewski over 2 years ago in reply to Bill Johns

Prodigy 50 points

Hi Bill,

Below is the schematic for the receiver side:

Note that the coil and tuning caps are shown as DNI, but we have wired in the coil and added caps.

The coil is custom design with the following parameters:

Dimensions (LWH): 15mm x 6.5mm x 2.67mm (1mm ferrite included in height)

L = 6.3uH @ 100kHz

DCR = 221mohm

Q = 12

It is designed to support up to 5W.

We've tuned the coil with the following capacitor values:
LC tank (C8, C9, C12): 0.22uF + 0.033uF + 0.01uF
Comms (C0, C11): 3900pF + 220pF

Let me know if you need additional info.

Best,
Matt

0 Nick Brylski over 2 years ago in reply to Matt Staniszewski

TI__Mastermind 19195 points

Hi Matt,

We have a faq that goes over ways to identify the root cause, could you check it out?

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/905835/faq-why-is-wireless-power-rx-device-overheating

We can review your coil schematic in the mean time.

Thanks,

Nick

0 Matt Staniszewski over 2 years ago in reply to Nick Brylski

Prodigy 50 points

Hi Nick,

Yes I looked at the FAQ. We extended our coil with wires and still experienced the heating. As for the conversion issues and the cap values, we've tried tuning a number of coils and all of them have the same issue despite the connection working. I did run up and down a range of LC tank cap values with one coil and recorded the power loss, and from what I saw over a range of about 100nF around my tuned value, there was little improvement.

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BQ51003: Transmit side overheating