BQ500211A Datasheet, PDF (11/27 Pages) Texas Instruments – 5-V, WPC1.1 Compliant Wireless Power Transmitter Manager

bq500211A
www.ti.com
Application Information
SLUSBB1 – DECEMBER 2012
Coils and Matching Capacitors
The coil and matching capacitor selection for the transmitter has been established by WPC standard. This is
fixed and cannot be changed on the transmitter side.
An up to date list of available and compatible A5 and A11 transmitter coils can be found here (Texas Instruments
Literature Number SLUA649):
Capacitor selection is critical to proper system operation. A total capacitance value of 400 nF is required in the
resonant tank. This is the WPC system compatibility requirement, not a guideline, and must be followed.
NOTE
A total capacitance value of 400 nF/50 V (C0G dielectric type or equivalent) is required in
the resonant tank to achieve a 100-kHz resonance frequency.
The capacitors chosen must be rated for at least 50 V and must be of high quality C0G dielectric or equivalent.
These are typically available in a 5% tolerance. 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 requirement,
might fail.
A 400-nF capacitor is not a standard value and therefore several must be combined in parallel. The designer can
combine a (4 nF x 100 nF) or a (180 nF + 220 nF) along with other combinations depending on market
availability. All capacitors must be of high quality C0G type or equivalent and not mixed with lesser dielectric
types.
Dynamic Power Limiting™
Dynamic Power Limiting™ (DPL) allows operation from a 5-V supply with limited current capability (such as a
USB port). There are two modes of operation selected via an input pin. In the dynamic mode, when the input
voltage is observed drooping, the output power is limited to reduce the load and provides margin relative to the
supply’s capability. The second mode, or constant current mode, is designed specifically for operation from a
500-mA capable USB port, it restricts the output such that the input current remains below the 500-mA limit.
NOTE
Pin 4 must always be terminated, else erratic behavior may result.
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 WPTX in DPL mode
will respond to this CEP via the normal WPC control loop.
NOTE
Depending on LED_MODE selected, the power limit indication may be either solid amber
(green + red) or solid red.
Copyright © 2012, Texas Instruments Incorporated
Product Folder Links: bq500211A
Submit Documentation Feedback
11