P9222-R/RN Datasheet

© 2019-2022 Renesas Electronics Corporation

19

May 5, 2022

5.4 Power Transfer

Once the “identification and configuration” phase is completed then the transmitter initiates the power transfer mode. The P9222-R/RN control

circuit measures the rectifier voltage, sends CEPs to the transmitter to adjust the rectifier voltage to the level required to maximize the efficiency

of the linear regulator, and sends Received Power Packets (RPPs) to notify the Tx of the current for foreign object detection (FOD) to guarantee

safe, efficient power transfer. For more information about WPC-compliant power transfer, see “WPC-Compliant Power Transfer.”

5.5 Synchronous Rectifier

The efficiency of the full-bridge rectifier in the P9222-R/RN is increased by operating in full synchronous rectifier mode. The rectifier is comprised

of four self-driven switches that work in a full synchronous mode of operation when the load is higher than a programmable level (typically

150mA for BPP operation). Below that threshold, the rectifier works in half-synchronous rectification mode. At power-up, when the voltage is

below the UVLO threshold, the rectifier functions by using the body diodes associated with the NMOS transistors. The BST capacitors are used

to provide power to drive the gates of the high-side NMOS switches.

5.6 Over-Voltage Protection

In the event that the input voltage increases above 15V (default setting), the Rx sends control error packets to the transmitter in an attempt to

bring the rectifier voltage back to a safe operating voltage level while simultaneously clamping the incoming energy using the internal high

voltage OVP FET for VRECT over-voltage clamping control. The clamp is released when the VRECT voltage falls below the VOVP hysteresis

falling level. The P9222-R/RN also sends interrupts to the application processor (AP) when the over-voltage event occurs.

5.7 Over-Current Protection and Thermal Shutdown

The P9222-R/RN uses over-current and thermal protection by sending an interrupt to the AP to notify the host controller if the output current or

die temperature has exceeded the operating limits. In the event that an overcurrent condition exists, the interrupt is sent to the AP with the

expectation that it will respond by reducing the output consumption being drawn from the P9222-R/RN. If the overcurrent condition persists and

is not corrected, then P9222-R/RN die temperature increases can be expected. In the event that the die temperature exceeds the thermal

shutdown level, an End Power Transfer packet is sent to the transmitter to terminate power transfer and protect the P9222-R/RN from thermal

stress. The current limit level is programmable. The P9222-R/RN sends interrupts to the AP if the current limit is reached or the die temperature

reaches elevated levels to allow the AP an opportunity to reduce the load current in order to prevent power transfer interruptions.

5.8 External Temperature Sensing

The P9222-R/RN includes an optional temperature sense input pin on GP0. It is used to monitor a remote temperature, such as on an Rx coil

or a PC board using an external thermistor circuit shown in Figure 15.

The GP0 pin voltage can be calculated using the following equation,

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Equation 1

where NTC is the thermistor’s resistance (RTH1) and R21 is the pull-up resistor connected to the 1.8V (LDO1P8) supply voltage on the

P9222-R/RN Evaluation Board. The over-temperature interrupt is triggered if the voltage on the GP0 pin is lower than 0.6V. The RTH1 is not

populated on the P9222-R/RN Evaluation Board.