P9242-R Datasheet, PDF (16/31 Pages) Integrated Device Technology – Wireless Power Transmitter

Table 6. LED Pattern Selection
Option
1
2
3
4
5
6
7
Voltage on LED_PAT Pin
Pull-Down or 0.075V
0.225V
0.375V
0.525V
0.675V
0.825V
0.975V or Pull-Up
P9242-R Datasheet
LED1/LED2 Pin
LED1 – GREEN
LED2 – RED
LED1 – GREEN
LED2 – RED
LED1 – GREEN
LED2 – RED
LED1 – GREEN
LED2 – RED
LED1 – GREEN
LED2 – RED
LED1 – GREEN
LED2 – RED
LED1 – GREEN
LED2 – RED
Standby
Off
Off
On
On
Off
Off
Off
Off
On
On
Off
Off
Off
Off
Status
Transfer Complete
On
Off
Off
Off
On
Off
Off
Off
Blink 1Hz
On
Off
Off
On
Off
Off
Off
Blink 1Hz
On
Off
Off
Off
On
On
Off
Blink 1Hz
On
Off
Off
Fault
Off
Blink 4Hz
Off
Blink 4Hz
Blink 4Hz
Off
Blink 4Hz
Off
Off
Blink 4Hz
Off
Blink 4Hz
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.
© 2016 Integrated Device Technology, Inc
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December 16, 2016