BQ500414Q Datasheet, PDF (18/34 Pages) Texas Instruments – Qi Compliant Wireless Power Transmitter Manager

bq500414Q
SLUSBE4B – JANUARY 2014 – REVISED JUNE 2014
Device Functional Modes (continued)
Rectifier
Receiver Coil
Receiver
Capacitor
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Modulation
Capacitors
Amax
A(0)
Operating state at logic “ 0”
Comm
A(1)
Operating state at logic “ 1”
Fsw
Fo(1) < Fo(0)
F, kHz
a)
b)
Figure 8. Receiver Capacitive Modulation Circuit
8.4.3 Power Trains
The bq500414Q drives three independent half bridges. Each half bridge drives one coil from the coil set
assembly. The TPS28225 is the recommended driver device for this application. It features high-side drive
capability which enables the use of N-channel MOSFETs throughout. Gate-drive supply can be derived from a
primitive active voltage divider. A highly regulated supply is not required to drive MOSFET gates.
8.4.4 Signal Processing Components
The COMM signal used to control power transfer is derived from the coil voltage. Each coil has its own signal
processing chain. The AC coupled coil voltage is scaled down to a manageable level and biased to a 1-V offset.
Series connected diodes are provided for protection from any possible transients. The three signal processing
chains are then multiplexed together via analog switches. Thus, the correct signal processing chain and COMM
signal used to control power transfer is from the coil being driven.
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