Data Sheet Rev. G, November 2023 | Subject to change without notice

6 of 16

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ACT4529

40 V/3.0 A CV/CC Buck Converter Featuring QC2.0, USB Auto-Detect and USB-PD

®

FUNCTIONAL BLOCK DIAGRAM

FUNCTIONAL DESCRIPTION

Output Current Sensing and Regulation

Sense resistor is connected to CSP and CSN. The

sensed differential voltage is compared with interval

reference to regulate current. CC loop and CV loop are

in parallel. The current loop response is allowed to have

slower response compared to voltage loop. However,

during current transient response, the inductor current

overshoot/undershoot should be controlled within +/-25%

to avoid inductor saturation.

Cycle-by-Cycle Current Control

The conventional cycle-by-cycle peak current mode is

implemented with high-side FET current sense.

Input Over Voltage Protection

The converter is disabled if the input voltage is above

42 V (+/-2 V). Device resumes operation automatically

40 ms after OVP is cleared.

Output Over Voltage Protection

Device stops switching when output over-voltage is

sensed, and resumes operation automatically when

output voltage drops to OVP- hysteresis.

Output Over Voltage Discharge

Discharge circuit starts to discharge output through

CSP pins when output over voltage is detected.

Discharge circuit brings 12 V down to 5 V in less

than 100 ms.

Output Under-Voltage Protection / Hiccup

Mode

There is a under voltage protection (UVP) threshold. If

the UVP threshold is hit for 10 us, an over current or

short circuit is assumed, and the converter goes into

hiccup mode by disabling the converter and restarts

after hiccup waiting period.

Input Brownout Protection

(ACT4529YH-T1011 only)

If the input voltage drops below 8 V but higher than

UVLO for 450 ms while in QC or PDC mode, the output

voltage turns off and QC or PDC mode is disabled. If the

output voltage drops below 3.7 V, the timer restarts and

waits for 450 ms before attempting to restart the output

voltage. When output voltage rises above 3.9 V and

detects the input voltage below 8 V, timer restarts. If the

input voltage is below 8 V after 450 ms, the output turns

off. The cycle continues until the input voltage increases

above 8.2 V,for longer than 450 ms, then output turns

on, the IC renegotiates the PD and QC protocols, and

normal operation restarts.

Thermal Shutdown

If the TJ increases beyond 160 °C, ACT4529 goes into

HZ mode and the timer is preserved until TJ drops

by 30 °C.

PWM

Controller

Driver

Current Sense

and Control

70m

Ω

4.7

Ω

OVP

CSP

CSN

GND

SW

HSB

UVLO

VIN

DP

DM

QC2.0

Detect

USB

Auto

Detect

PDC