Datasheet

bq500410A

SLUSB96 – NOVEMBER 2012

www.ti.com

Input Power Requirements

For full wireless power system capability and WPC compliance, the AC power adapter selected for the

application should have a minimum rating of 12 V at 750 mA.

PCB Layout

Careful PCB layout practice is critical to proper system operation. There are many references on proper PCB

layout techniques. A few good tips are repeated here:

The TX layout requires a 4-layer PCB layout for best ground plane technique. A 2-layer PCB layout can be

achieved though not as easily. Ideally, the approach to the layer stack-up has been:

• Layer 1 component placement and as much ground plane as possible.

• Layer 2 clean ground.

• Layer 3 finish routing.

• Layer 4 clean ground.

Thus, the circuitry is virtually sandwiched between grounds. This minimizes EMI noise emissions and also

provides a noise free voltage reference plane for device operation.

Keep as much copper as possible. Make sure the bq500410A GND pins and the power pad have a continuous

flood connection to the ground plane. The power pad should also be stitched to the ground plane, which also

acts as a heat sink for the bq500410A. A good GND reference is necessary for proper bq500410A operation,

such as analog-digital conversion, clock stability and best overall EMI performance.

Separate the analog ground plane from the power ground plane and use only ONE tie point to connect grounds.

Having several tie points defeats the purpose of separating the grounds!

The COMM return signal from the resonant tank should be routed as a differential pair. This is intended to reduce

stray noise induction. The frequencies of concern warrant low-noise analog signaling techniques, such as

differential routing and shielding, but the COMM signal lines do not need to be impedance matched.

The DC-to-DC buck regulator used from the 12-V input supplies the bq500410A with 3.3 V. Typically a single-

chip controller solution with integrated power FET and synchronous rectifier or outboard diode is used. Pull in the

buck inductor and power loop as close as possible to create a tight loop. Likewise, the power-train, full-bridge

components should be pulled together as tight as possible. See the bq500410A EVM for an example of a good

layout technique.

References

1. Technology, Wireless Power Consortium, http://www.wirelesspowerconsortium.com/

2. Analog Applications Journal, An Introduction to the Wireless Power Consortium Standard and TI’s Compliant

Solutions, Johns, Bill, (Texas Instruments Literature Number SLYT401)

3. Datasheet, Qi Compliant Wireless Power Transmitter Manager, (Texas Instruments Literature Number

SLUSAL8)

4. Datasheet, Integrated Wireless Power Supply Receiver, Qi (WPC) Compliant, bq51011, bq51013, (Texas

Instruments Literature Number SLVSAT9)

5. Application Note, Building a Wireless Power Transmitter, (Texas Instruments Literature Number SLUA635)

6. Application Note, bqTESLA Transmitter Coil Vendors, Texas Instruments Literature Number SLUA649

Product Folder Links: bq500410A