AP3303

Document number:DS41016 Rev. 5 - 2

10 of 16

www.diodes.com

May 2019

© Diodes Incorporated

AP3303

Operation Description (continued)

Figure 2

Active Frequency Dithering

To improve the EMI performance, the AP3303 integrates an active frequency dithering function. A consecutive frequency-dithering signal is

injected to the SENSE pin after Leading-Edge Blanking (LEB) time. As shown in Figure 3, the frequency-dithering signal is repeating over and

over again with a period of

ms and amplitude of +/-VS_JITTER. With the injection of frequency-dithering signal on SENSE pin, the switching

frequency will have a periodical excursion to improve the EMI performance.

SENSE

LEB

From FB

0

Jitter

PWM

Comparator

Figure 3

Current Mode PWM Control

The AP3303 operates as a current mode controller; the output switch is turned on by every oscillator cycle and turned off when the primary peak

current reaches the threshold level established by the FB pin. The primary current signal is converted to a voltage signal on current sense

resistor RS. The relation between primary peak current (IPK) and VFB is:

S

FB

PK

R

V

I

4

/



20kHz

120kHz