AP3790

Document number: DS37221 Rev. 3 - 2

9 of 17

www.diodes.com

October 2014

© Diodes Incorporated

AP3790

A Product Line of

Diodes Incorporated

Light Load

Medium Load

High Load

fsw

22kHz

2kHz

60kHz

37%

4%

100%

12kHz

4kHz

Figure 4. Multiple Segment Peak Current at CV Mode

It can be seen from Figure 4, with multiple segment peak current control, AP3790 power system can get the good audible noise performance.

Leading Edge Blanking (LEB) Time

When the power switch is turned on, a turn-on spike will occur on the sense-resistor. To avoid false turn off switch, a 500ns leading-edge

blanking is built in. During this blanking time, the current sense comparator is disabled and the external power switch cannot be turned off.

Therefore the LEB time parameter also changes with different load condition.

Adjustable Line Compensation and Fixed Cable Compensation

The AP3790 power system can adjust line compensation by changing the upper resistor at FB pin. The line compensation capability is

increased by decreasing the resistance of the upper FB resistor.

Cable compensation is fixed in AP3790.

Valley Turn-on

which is result from the equivalent output capacitance. At the same time, because of valley turn on the switching frequency has the random jitter

feature, which will be benefit for conductive EMI performance. And valley turn on can also reduce the power switch turn on spike current and

then result in the better radiative EMI performance.

Frequency Jitter

Even though the valley turn on function can lead the random frequency jitter feature, an active frequency jitter function is added to AP3790 to

sequence, the active frequency jitter can be realized with 256

μs repetitive cycles.