P9412 Datasheet

R35DS0011EU0120 Rev.1.2

Jul.6.21

Page 16

3.11

Operating Configurations (Bypass and Capacitor Divider)

The P9412 has three operating configurations: Bypass Mode, Capacitor Divider Mode, and Disable Mode. Upon

start-up and connection to a Tx, or in TRx mode, the P9412 will enter Bypass mode (VOUT = CPOUT) and the

CPOUT voltage is limited to 3.5V to 12V. Load can be immediately applied at start-up in Bypass mode when

CPOUT good interrupt is sent. In order to transition to Capacitor Divider configuration, the P9412 must first enter

disable mode in order to start up the capacitor divider. This interim transition mode (Disable) is not user

configurable and the P9412 firmware will automatically enter and leave Disable mode when the AP requests a

change from Bypass to Capacitor Divider or Capacitor Divider to Bypass configuration. Starting the capacitor

divider requires all loading on CPOUT to be removed and then pre-charging the CFLY capacitor and CPOUT

capacitor to ½ the VOUT voltage using internal current sources (10mA). The host AP should update the

appropriate register after removing the load from CPOUT to initiate configuration changes. The P9412 will not

change operating configuration if there is a load applied to CPOUT and an alarm will be issued. After the load is

removed and the AP requests the configuration change, the P9412 will automatically start operating in Capacitor

Divider mode and signal to the host AP that CPOUT is good and loading may commence. The request to

transition between states is handled via I2C register request, and all settings and control are internally controlled

by firmware and are not end-user configurable.

3.12

V5P0AP and V1P8_AP Inputs

In high-power applications where VRECT voltage is expected to be higher than 5V, the power dissipation from

the internal 5V LDO is proportional to the difference between the VRECT voltage and LDO5P0 output voltage

multiplied by the P9412 active quiescent current plus current required to switch the internal N-FETs. In order to

reduce this increasing power loss, an external 5V supply can be provided to the P9412 through the V5P0AP pin.

An internal back-to-back FET is connected between the V5P0AP and LDO5P0 pins for isolation.

When using the V5P0_AP pin to reduce power consumption for high output voltage charging, it is recommended

to apply the voltage to the pin after power-up, and remove the external power supply before or shortly after

wireless power transfer or the connection is terminated. The host AP should enable the V5P0_AP source

selection by register when used.

The V1P8_AP input is used to power the integrated Digital Ping Detect circuit and should be connected to the

host AP 1.8V power supply so that the Ping Detect function may be used.

3.13

WPC Mode Characteristics

3.13.1.

Start-Up

When a mobile device containing the P9412 is placed on a WPC Qi certified charging pad, it responds to the

transmitter’s “ping” signal by rectifying the AC power from the transmitter and storing it on a capacitor connected

to VRECT. During the “Ping” phase, once the rectifier provides voltage at the VRECT pin above the UVLO

threshold, the digital section of the P9412 enables communication. The control loop of the P9412 adjusts the

rectifier voltage by sending error packets to the transmitter before and after it enables the VOUT MLDO.

The VOUT MLDO is enabled when the power transfer mode is initiated and the voltage at VRECT, the output of

the full-wave synchronous rectifier reaches the target voltage that includes headroom in addition to the LDO

VOUT target voltage. For example, if the VOUT voltage target is 12 V, the target VRECT voltage is VOUT +

headroom, where headroom is a function of the output current. The P9412 Capacitor Divider is set in bypass

mode at startup and may be loaded immediately upon power-up. The FW_Inhibit input or the enable pin of the

P9412 can be asserted to shut down the P9412 which will disable the entire device and place it in a low current

(sleep) mode and the P9412 will not respond to wireless digital ping or send power when in a shutdown state.

3.13.2.

Power Transfer

Once the “identification and configuration” phase is completed and successful, “negotiation and calibration” is

accomplished then the system enters power transfer mode. The P9412 control circuit measures the rectifier

voltage and sends error packets to the transmitter to adjust the rectifier voltage to the level required to maximize