Reference design enables Qi wireless charging transmitters

17th March 2015
Siobhan O'Gorman


A reference design for 5V low power Qi wireless charging transmitters has been introduced by NXP Semiconductors. Compliant with the Wireless Power Consortium (WPC) 1.1 Qi specification, the design is based on the company’s single-chip 5V wireless power transmitter IC, the NXQ1TXA5.

Building on NXP’s success as the market leader in Greenchip power ICs, the NXQ1TXA5 reference design has an outstanding standby power consumption of less than 10mW. The design is the only solution on the market today that meets 5-star mobile phone charger standby power ratings by consuming less than 30mW in standby mode, which includes the standby power of the wall-charger. The company recommends combining the transmitter solution with another Greenchip device, its high efficiency TEA1720 SMPS IC with a standby power of less than 20mW.

The NXQ1TXA5 device combines NXPs patented high efficiency Class D amplifier technology for outstanding EMI performance, and CoolFluxTM DSP technology for superior communication with smartphones placed on the charger. The design also features dedicated low power mixed signal circuitry to check for smartphone presence three times per second, enabling fast startup of charging, while keeping the standby power very low if there is no smartphone on the charger.

Due to the low power consumption of the NXQ1TXA5 device itself, the reference design also has a high efficiency for low transmitted powers, making it suitable for applications ranging from smartphone charging to deliver 5W to the smartphone battery when used with a Qi compliant wireless charging receiver, to chargers for wearables that need less than 2W charging power.

The NXQ1TXA5 reference design needs only 15 to 20 low cost passive components and uses a standard 2-layer PCB, with the components mounted on a single side. Depending on customer requirements, the complete application can be designed on a board space as small as 3x3 or 4x4cm.

“With this highly optimised and very cost efficient solution for a Qi wireless charging transmitter, NXP enables manufacturers to include a wireless charger with their smartphones and wearable devices at low cost. This allows their customers to immediately enjoy the advantages of the wireless charging feature of their products at the moment of unpacking their latest purchase, saving them the effort of buying it as an accessory.” said Marcel van Roosmalen, Power Solutions Segment Manager, NXP Semiconductors.

NXP will highlight its wireless charging/LLC solutions at booth 1101 during APEC, held from 15th to 19th March in Charlotte, North Carolina.

The NXQ1TXA5 wireless charging transmitter reference design will be available in Q2 2015.

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