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AN11524 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2015. All rights reserved.
Application note Rev. 1 — 17 February 2015 13 of 54
NXP Semiconductors
AN11524
NXQ1TXA6 Evaluation Board
5.1 NXQ1TXA6 charging controller
The NXQ1TXA6 is a wireless charger controller for A6 type base stations. It offers WPC
1.1 Qi-compliant communication and safety functions including Foreign Object Detection
(FOD), over-temperature protection and more. The controller supports ping mode during
standby to detect potential mobile devices. It also works with the NXP NT3H1201 to
enable tap to power on with an NFC enabled phone.
Settings are available via resistor networks for Foreign Object Detection (FOD) level, LED
blinking and other options. Refer to NXQ1TXA6 data sheet for further information.
5.2 Half Bridge driver
There are 3 half-bridge driver stages in the NXQ1TXA6 Evaluation Board. Control signals
EN_HB1, EN_HB2 and EN_HB3 enable the driver stages independently. At any one time,
only one driver stage is enabled for either pinging to detect the presence of a mobile
device or active charging. The half-bridge driver stage is designed to output about ~7 W
power to ensure minimum 5 W output is received at the mobile device.
NXP NWP2081T half-bridge controller IC and NX2020N2 N-channel Trench MOSFETs
are the two key semiconductor components. They drive the A6 type primary coil and
series capacitance (LC tank circuit) at operating frequency between 115 kHz to 205 kHz.
Frequency and duty cycle is varied via Pulse-Width Modulated (PWM) signal from the
NXQ1TXA6 charging controller
The NXQ1TXA6 Evaluation Board can be configured to support A6 type single coil base
station by shorting R117 and R118 in
Figure 7 to ground. In this configuration, only
half-bridge driver for coil 1 is active. Resistors R117 and R118 are not populated for an A6
type 3-coil base station configuration.
5.3 Amplitude-Shift Keying (ASK) envelope demodulator
One-directional communication from the mobile device to the base station is achieved via
back-scattered Amplitude-Shift Keying modulation as illustrated in
Figure 1 .
The mobile device modulates the magnetic field of the base station using either capacitive
or resistive load, at a rate of 2 kbits/sec.
An envelope detector is used to demodulate the communication data. The demodulated
output is sent to the NXQ1TXA6 charging controller for further processing.
High voltages up to 100 V
p-p
can be observed at the input of the envelope detector.
5.4 +12 V universal mains adapter
The power supply design is based on NXP TEA1720 low cost Switched Mode Power
Supply (SMPS) controller IC. It is optimized for fly back converter topology to provide
high-efficiency over the entire load range with ultra-low power consumption in the no-load
condition.