Classification | PRIVATE

Data Sheet Rev. B, January 2025 | Subject to change without notice

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ACT4533A/B

Wide Input Sensorless CC/CV Step-Down DC/DC Converter

regulating output current, and the output voltage will

drop with increasing load.

The Oscillator normally switches at 125 kHz. However,

if FB voltage is less than 0.6 V, then the switching

frequency decreases until it reaches a typical value of

18 kHz at VFB = 0.15 V

Over Voltage Protection (ACT4533A)

The ACT4533A has an OVP pin. If the voltage at this

pin exceeds 0.8 V, the IC shuts down the high-side

switch. There is a 4 µA pull-up current at this pin.

EN/OVP Pin (ACT4533B)

The ACT4533B has an enable input and OVP input for

turning the IC on and off.

If the voltage at this pin rises above 0.65 V, the IC is

enabled. The EN contains a 60mV hysteresis and 4 µA

pull-up current source.

If the voltage at this pin is between 0.65 V and 2.26 V,

the IC operates normally; if the voltage at this pin

exceeds 2.26 V, the IC shuts down high-side switch.

The OVP contains a 500mV hysteresis and 4 µA

pull-up current source.

Thermal Shutdown

The ACT4533A/B disables switching when its junction

temperature exceeds 155 °C and resumes when the

temperature has dropped by 25 °C.