ANP015 Datasheet, PDF (11/15 Pages) List of Unclassifed Manufacturers – Application Note AP2011 High Efficiency Synchronous PWM Controller

Application Note
AP2011 High Efficiency Synchronous PWM Controller
ANP015
Preliminary
3. Design Procedure
3.1 Introduction
The AP2011 integrated circuit is a synchronous PWM controller, it operates over a wide input
voltage range. Being low cost, it is a very popular choice of PWM controller. This section will describe
the AP2011 design procedure. The operation and the design of this application will also be discussed in
detail.
3.2 Operating Specifications
Specification
Input Voltage
Output Voltage
Operating Frequency
Output power
Min
Typ
18
20
4.9
5
160
180
0
25
Table 1. Operating Specifications
Max
Units
22
V
5.1
V
200
KHz
30
W
3.3 Design Procedures
This section describes the steps to design synchronous buck converter, and explains how to
construct basic power conversion circuits including the design of the control chip functions and the basic
loop.
z Synchronous buck converter
Example calculations accompany the design equations. Since this is a buck output system, this
example calculations apply to the converter with output power is 60W and input voltage set to 25V,
unless specified otherwise. The first quantity to be determined is the converter the duty cycle value.
Duty ratio D =
+ V V o
DS(sat),N
– + V V V IN
DS(sat),P
DS(sat),N
=
Ton
Ts
, 0≦D≦1
Assuming the low-side N-channel MOSFET switch-on voltage VDS(sat),N = 0.1 V, the high-side
P-channel MOSFET switch on voltage VDS(sat),P = 0.1V and Vo = 5V. In this case the duty cycle for VIN =
20V is 0.255 for 5V/5A output system.
Anachip Corp.
www.anachip.com.tw
11/15
Rev. A.0 Oct, 29, 2004