BQ500412 Datasheet, PDF (11/28 Pages) Texas Instruments – Low System Cost, Wireless Power Controller for WPC TX A6

bq500412
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SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013
Application Information
Coils and Matching Capacitors
The coil and matching capacitor selection for the transmitter has been established by WPC standard. These
values are fixed and cannot be changed on the transmitter side.
An up to date list of available and compatible A6 transmitter coils can be found here (Texas Instruments
Literature Number SLUA649):
Capacitor selection is critical to proper system operation. The total capacitance value of 147nF is required in the
center coil of the resonant tank. This capacitance is not a standard value and therefore several must be
combined in parallel. It is recommended to use 100nF + 47nF, as these are very commonly available.
NOTE
A total capacitance value of 147nF/100 V/C0G is required in the center coil and
133nF/100V/C0G in the side coils of the resonant tank to achieve the desired resonance
frequency.
The capacitors chosen must be rated for 100 V operation. Use quality C0G type dielectric capacitors from
reputable vendors such as KEMET, MURATA or TDK.
Dynamic Power Limiting™
With an optional 5-V to 12-V boost converter, a 5-V input can enable a 12-V WPC A6 transmitter. The Dynamic
Power Limiting™ (DPL) feature allows operation from a 5-V supply with limited current capability (such as a USB
port). When the 5-V input voltage is observed drooping, the output power is dynamically limited to reduce the
load and provides margin relative to the supply’s capability.
Anytime the DPL control loop is regulating the operating point of the transmitter, the LED will indicate that DPL is
active. The LED color and flashing pattern are determined by the LED Table. If the receiver sends a Control
Error Packet (CEP) with a negative value, (for example, to reduce power to the load), the transmitter in DPL
mode will respond to this CEP via the normal WPC control loop.
NOTE
The power limit indication depends on the LED_MODE selected.
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