5W, QI WIRELESS POWER RECEIVER WITH INTEGRATED RECTIFIER AND LDO OUTPUT

12

09/01/15

P9025AC DATASHEET

Bit Encoding Scheme

As required by the WPC, the P9025AC uses a differential

bi-phase encoding scheme to modulate data bits onto the

Power Signal. A clock frequency of 2kHz is used for this

purpose. A logic ONE bit is encoded by generating two

transitions per clock period, whereas a logic ZERO bit is

encoded using only one transition per clock period as shown

below:

Figure 4. Bit Encoding Scheme

Each byte in the communication packet comprises 11bits in an

asynchronous serial format, as shown below:

Figure 5. Byte Encoding Scheme

Each byte has a start bit, 8 data bits, a parity bit, and a single

stop bit.

System Feedback Control

The P9025AC is fully compatible with WPC specification Rev.

1.1.2 and has all necessary circuitry to communicate with the

base station via WPC-compliant communication packets.

The overall WPC-compliant system behavior between the

transmitter and receiver follows the state machine below:

Figure 6. WPC System Feedback Control

The P9025AC goes through four phases: Start/Selection,

Ping, Identification & Configuration, and Power Transfer.

Start/Selection

In this phase, the P9025AC senses the incoming power from

the base station transmitter and proceeds to the PING state. It

monitors the rectified voltage, and when the voltage is above

electronics and prepares to communicate with the base

station. If the P9025AC does not proceed to PING, then it does

not transmit any communication packets.

Ping

In this phase, the P9025AC transmits a Signal Strength

Packet as the first communication packet to instruct the base

to keep the power signal ON. After sending the Signal

Strength Packet, the P9025AC proceeds to the Identification

and Configuration phase. If, instead, the P9025AC sends End

of Power Packets, then it remains in the PING phase.

In this phase, the P9025AC sends the following packets:

Identification and Configuration (ID & Config)

In this phase, the P9025AC may send the following packets:

After sending the Configuration Packet, the P9025AC

proceeds to the power transfer phase.

Power Transfer

In this phase, the P9025AC controls the power transfer from

the Power Transmitter by means of the following Control Data

Packets:

Modulation

The P9025AC is compatible with WPC V1.1.2 transmitter

coils. Each receiver coil type has a unique inductance value

and various physical properties as are best for a given

application. As such, the resonant capacitor (CS) that is used

with a given receiver coil should be optimized for the overall

application. The WPC guidance for Cs is that the resonant

frequency of the receiver coil and Cs capacitor should be

100kHz while placed on the surface of a transmitter with the

normal spacing.

ONE

ZERO

ONE

ZERO

ONE

ONE

ZERO

ZERO

Start

Stop

Parity

b

01

2

3

4

5

6

7

b

bbbb

b

b