P9242-R Datasheet

© 2016 Integrated Device Technology, Inc

16

December 16, 2016

Table 6.

LED Pattern Selection

Option

Voltage on LED_PAT Pin

LED1/LED2 Pin

Status

Standby

Transfer

Complete

Fault

1

Pull-Down or 0.075V

LED1 – GREEN

Off

On

Off

Off

LED2 – RED

Off

Off

Off

Blink 4Hz

2

0.225V

LED1 – GREEN

On

On

Off

Off

LED2 – RED

On

Off

Off

Blink 4Hz

3

0.375V

LED1 – GREEN

Off

Blink 1Hz

On

Blink 4Hz

LED2 – RED

Off

Off

Off

Off

4

0.525V

LED1 – GREEN

Off

On

Off

Blink 4Hz

LED2 – RED

Off

Off

Off

Off

5

0.675V

LED1 – GREEN

On

Blink 1Hz

On

Off

LED2 – RED

On

Off

Off

Blink 4Hz

6

0.825V

LED1 – GREEN

Off

Off

On

Off

LED2 – RED

Off

On

Off

Blink 4Hz

7

0.975V or Pull-Up

LED1 – GREEN

Off

Blink 1Hz

On

Off

LED2 – RED

Off

Off

Off

Blink 4Hz

7.9

Foreign Object Detection

When metallic objects, such as coins, keys, and paperclips, are exposed to alternating magnetic fields, the eddy current flowing through the

object will heat up. The amount of heat generated is a function of the amplitude and frequency of the magnetic field, as well as the

characteristics of the object, such as resistivity, size, and shape. In any wireless power system, the heat generated by the eddy current

manifests itself as a power loss reducing the overall system efficiency. If appropriate measures are not taken, the heating could lead to unsafe

situation.

In Extended Power Profile, there are two stages of foreign object detection (FOD). One is by measuring the system quality factor prior to

entering the power transfer phase, and the other is to measure the power loss difference between the received power and the transmitted

power during the power transfer phase. Prior to entering the power transfer phase, the P9242-R detects a change in the coil’s quality factor

(Q-factor) when a wireless power receiver or metal object has been placed on its surface. The transmitter measures the Q-factor and

compares it with the reference Q-factor provided by the receiver. If the difference is higher than the reference Q-factor, the P9242 will identify

it as FOD and shut down the system.

The second stage of the foreign object detection is during the power transfer where the power loss difference between the received power

and transmitted power is constantly measured and compared to the WPC-1.2.2-specified threshold. If the difference is higher than the

threshold set by the WPC specification, the system will shut down to avoid over-heating.