BQ500414Q Datasheet, PDF (20/34 Pages) Texas Instruments – Qi Compliant Wireless Power Transmitter Manager

bq500414Q
SLUSBE4B – JANUARY 2014 – REVISED JUNE 2014
www.ti.com
Typical Application (continued)
9.2.1 Design Requirements
9.2.1.1 Capacitor Selection
Capacitor selection is critical to proper system operation. The total capacitance value of 2 x 68-nF ( 2 x (68-nF +
5.6-nF) in the 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 x 68-nF (additional 2 x 5.6-nF center coil) (C0G dielectric
type, 100V rating) 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.
9.2.1.2 Current Monitoring Requirements
The bq500414Q is WPC1.1 ready. In order to enable the PMOD or FOD features, current monitoring must be
provided in the design.
For proper scaling of the current monitor signal, the current sense resistor should be 40-mΩ and the current
shunt amplifier should have a gain of 50, such as the INA213Q1. For FOD accuracy, the current sense resistor
must be a quality component with 1% tolerance, at least 1/4-Watt rating, and a temperature stability of ±200
PPM. Proper current sensing techniques in the application hardware should also be observed.
9.2.1.3 All Unused Pins
All unused pins can be left open unless otherwise indicated. Please refer to the Pin Functions table. Grounding
of unused pins, if it is an option, can improve PCB layout.
9.2.1.4 Input Regulators
The bq500414Q requires 3.3-V_DC to operate. A buck converter is used to step down from the automotive rail
voltage, such as the TPS54040 used in this design.
The power train bridge circuitry requires 12 V, and it is fed from a SEPIC converter using the TPS40210
controller. Since the automotive rail voltage can vary widely, this acts as a type of pre-regulator.
20
Submit Documentation Feedback
Product Folder Links: bq500414Q
Copyright © 2014, Texas Instruments Incorporated