Datasheet

bq500410A

www.ti.com

SLUSB96 – NOVEMBER 2012

The bq500410A

Description of Operation

The bq500410A pings the surroundings in 400-ms intervals by sequentially firing the three coils in the array. The

COMM feedback signal is multiplexed through analog switches and is synchronized to the coil being driven. To

select the best coil match, the bq500410A looks for the strongest COMM signal. The coil is engaged and driven,

note that only one coil is driven at a time. The driven coil is tolerant of slight misalignment of the RX while power

is being transferred. Actually displacing the RX to an adjacent coil while charging is allowable, the sequential

ping sequence and detection to determine the best matching coil to drive continues to repeat.

Capacitor Selection

Capacitor selection is critical to proper system operation. The total capacitance value of 2 nF x 68 nF (+5.6-nF

center coil) is required in the resonant tank. This is the WPC system compatibility requirement, not a guideline.

NOTE

A total capacitance value of 2 nF x 68 nF/100 V (68 nF + 5.6 nF center coil) (C0G

dielectric type) is required in the resonant tank to achieve the correct resonance

frequency.

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. The use of X7R types or

below is not recommended if WPC compliance is required because critical WPC Certification Testing, such as

the minimum modulation or ensured power requirements, 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.

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