AP8024 datasheet(7/11 Pages) AITSEMI

7 / 11 page

AiT Semiconductor Inc.

www.ait-ic.com

AP8024

AC-DC PFM CONTROLLER

NON-ISOLATED PFM CONVERTERS

REV2.0

- JAN 2015 RELEASED, MAR 2018 UPDATED -

- 7 -

DETAILED INFORMATION

The AP8024 consists of an integrated Pulse Frequency Modulator (PFM) controller and power MOSFET,

specifically designed for small power non-isolated switching power supply. AP8024 has internal high voltage

start-up circuit and complete intelligent protections including adjustable Over Current Protection (OCP), Under

Voltage Lockout (UVLO) and Over Temperature Protection (OTP). Excellent EMI performance could be

achieved with Pulse Frequency Modulation.

Start up

At start up, the internal high-voltage current source supplies 2.5mA current to charges the external VDD

capacitor. When VDD rises to VDDon, AP8024 starts switching and the internal high-voltage current source

stops charging the capacitor. After start up, the VDD voltage is supplied from output.

CV Operation Mode

In CV operation, AP8024 samples the feedback signal through VDD pin. While the feedback voltage remains

below VREF, the IC turns on the integrated MOSFET. When the current of the inductor reaches the peak

current limit (Ipeak), the integrated MOSFET is turned off. Figure1 and Figure 2 shows the operating

waveform of key nodes in continuous conduction mode (CCM) and discontinuous conduction mode (DCM).

Meanwhile, the IC integrates load compensation function to improve load regulation and CV accuracy.

Figure 1 Waveform if CCM mode

Figure 2 Waveform of DCM mode

In actual applications, VDD sampling voltage is affected by the forward drop of D2 in addition

PFM modulation

The IC operates in PFM mode, and Ipeak is set to decrease with the decrease of the IC operating frequency

(fsw). when the IC switching cycle increase 1us, Ipeak will decrease 13.3mA. As a result of the internal

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