BQ500414Q Datasheet, PDF (9/34 Pages) Texas Instruments – Qi Compliant Wireless Power Transmitter Manager

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8 Detailed Description
bq500414Q
SLUSBE4B – JANUARY 2014 – REVISED JUNE 2014
8.1 Overview
The principle of wireless power transfer is simply an open cored transformer consisting of transmitter (Tx) and
receiver (Rx) coils. The transmitter coil and electronics are typically built into a charger pad and the receiver coil
and electronics are typically built into a portable device, such as a cell-phone.
When the receiver coil is positioned on the transmitter coil, magnetic coupling occurs once the transmitter coil is
driven. The flux is coupled into the secondary coil which induces a voltage and current flows. The secondary
voltage is rectified, and power can be transferred effectively to a load, wirelessly. Power transfer can be
managed through any of various familiar closed-loop control schemes.
The bq500414Q sends an analog ping to detect the presence of a receiver on the pad. An external enable trigger
or proximity detector can also be used to provide the means of detecting the presence of a receiver. The detector
can output an enable signal to the regulator supplying the bq500414Q and the device powers up, or the enable
signal can start the Tx via I²C command. Once the bq500414Q is active, it pings the three coils sequentially to
detect and power up the Rx. Once the Rx is powered up, it sends the communication packages to the Tx. The
package information can be fetched by the Tx through demodulating the COMM feedback signal, which is a
scaled version of primary coil voltage. The COMM feedback signal is multiplexed through analog switches and is
synchronized to the coil being driven. To select the best coil match, the bq500414Q looks for the strongest
COMM signal. 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.
bq500414Q provides I²C interface to support some read and write commands, which can also be used to start
the Tx and temporarily shift the Tx operating frequency.
8.2 Functional Block Diagram
COMM_A+ 37
COMM_A- 38
COMM_B+ 39
COMM_B- 40
COIL_PEAK 1
V_SENSE 45
I_SENSE 42
T_SENSE 2
LOSS_THR 43
LED_MODE 44
bq500414Q
Digital
Demodulation
Digital I/O
Controller
PWM
12-bit
ADC
POR
5
RESET
Buzzer
Control
I²C
6 PMOD
7 LED_A
8 LED_B
9 LED_C
22 FOD_CAL
25 COIL_SEL
18 ~ EN_PWR
13 FOD
21 EMI_SHIELD
12 DPWM-A
15 COIL 1.1
16 COIL 1.2
17 COIL 1.3
23 BUZ_AC
24 BUZ_DC
11 PMB_DATA
10 PMB_CLK
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