Table 4. Design Parameters

9.2.2.1 Capacitor Selection

Capacitor selection is critical to proper system operation. The total capacitance value of 2 × 100 nF + 47 nF is required in the resonant tank. This is the WPC system compatibility requirement, not a guideline.

The capacitors chosen must be rated for at least 100 V and must be of a high-quality C0G dielectric (sometimes also called NP0). These are typically available in a 5% tolerance, which is adequate. TI does not recommend the use of X7R types or below if WPC compliance is required because critical WPC Certification Testing, such as the minimum modulation or guaranteed power test, might fail.

The designer can combine capacitors to achieve the desired capacitance value. Various combinations can work depending on market availability. All capacitors must be of C0G types (not mixed with any other dielectric types).

9.2.2.2 Current Monitoring Requirements

The bq501210 is WPC v1.2 ready. To enable the PMOD or FOD features, provide current monitoring in the design.

For proper scaling of the current monitor signal, the current sense resistor should be 20 mΩ and the current shunt amplifier should have a gain of 50, such as the bq500100 (SBOS765). For FOD accuracy, the current sense resistor must be a quality component with 0.5% tolerance, at least 1/4-W rating, and a temperature stability of ±200 PPM. Proper current sensing techniques in the application hardware should also be observed.

9.2.2.3 All Unused Pins

All unused pins can be left open unless otherwise indicated. Refer to the table in Pin Configuration and Functions. To improve PCB layout, ground unused pins, if it is an option.

9.2.2.4 Input Regulators

The bq501210 requires 3.3 V_DC to operate. A buck converter is used to step down from the supply voltage, such as the TPS54231D used in this design.

9.2.2.5 Input Power Requirements

The bq501210 system works with 5-V to 19-V input voltage. Levels between 15 V and 19 V will deliver 15 W, which is required for a WPC Extended Power Profile (EPP) transmitter.

5-V input supplies are aimed to negotiate to HVDCP voltages of 9 V or 12 V which enables Fast Charging of capable receivers. The system may also deliver power as a normal 5-V transmitter, however, the power level will be reduced and provinging power to higher voltage receivers may not be successful. A typical 5-V receiver has shown to produce 4.5 W consistently. Coupling and other factors will greatly influence the results of each system.

9.2.2.6 LED Mode

The bq501210 can directly drive three LED outputs (LED-A, LED-B, and LED-C). Select one of the desired LED indication schemes by choosing the selection resistor connected between LED_MODE and GND.