AP43771

Document number: DS41431 Rev. 6 - 3

7 of 10

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June 2022

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AP43771

Performance Characteristics

System Power-On Sequence:

When the external power source is provided, the AP43771 will wake up, and the USB PD controller and MCU will be initialized. All analog control

blocks are ready and waiting for PD negotiation process. Meanwhile, the AP43771 monitors the voltage and current conditions to prevent

abnormal conditions from happening. Once any unacceptable condition happens, the AP43771 will go into protection procedure according to the

types of abnormal conditions.

Voltage Transition

According to USB PD’s protocol, the PD device requests different power profile and the AP43771’s power control blocks will change voltage and

current values. The AP43771 provides corresponding Over Voltage Protection (OVP), Over Current Protection (OCP) scheme, and feedback

system stability to guarantee monotonic voltage transition and avoid violating USB PD electrical specification.

The AP43771 provides zero-mismatch voltage methodology that is more flexible for customer system design requirement. When UFP/DFP makes

an acceptable power request deal, the AP43771 will change the VFB pin voltage according to the USB PD command. The voltage regulator

control loop regulates the required VBUS voltage according to VFB. In addition, the shunt regulator is built in to minimize the total external

components and cost.

Protection

The AP43771 provides OVP/UVP/OCP/SCP/OTP functions and also support Constant Current (CC) function. All of the protection thresholds

depend on the requested power profile, and provide the most reliable protection scheme.

The AP43771 provides OVP feature by turning off the power switch when VBUS is higher than OVP enable voltage. Meanwhile, it provides internal

discharge path to reduce the overvoltage duration, and terminates discharge current as soon as VBUS reaches the target voltage. To prevent the

VBUS pin from working abnormally, the AP43771 provides UVP function whenever VBUS drops to UVP enable voltage.

To ensure the safe operation of USB PD, the AP43771 provides programmable OCP function to make sure output current will not be higher than

the allowed maximum current. Once OCP conditions happen, the AP43771 will shut down the USB

PD system and send “Hard Reset” to the

Upstream-Facing Port (UFP) device.

CV/CC

The AP43771 supports Constant Voltage (CV) and Constant Current (CC) functions to control the output voltage and the output current by the

control pin OCDRV. During the CV mode, the AP43771 operates in fixed PDO, and the output voltage will be regulated to the requested voltage if

the output current is below the allowed maximum current. Once the sink device draws more than IOCP, the over current protection will be triggered.

When the CC mode function is enabled, the output voltage drops, and the source current is limited within 150mA whenever output current exceeds

the allowed maximum current. When the output voltage drops below UVP, constant current limit turns off VBUS and starts error recovery procedure.

The AP43771 will reset if the voltage continues dropping to UVLO threshold.