iW1706

Low-Power Off-Line Digital Green-Mode PWM Controller

iW1706

1.0 Features

● Primary-side feedback eliminates opto-isolators and

simplifies design

● Adaptively controlled soft start-up enables fast and

smooth start-up for a wide range of capacitive loads

(from 330 μF to 6000 μF)

● Very tight constant voltage regulation

● Intrinsically low common mode noise

● Optimized 72 kHz maximum PWM switching frequency

achieves best size and efficiency

● Adaptive multi-mode PWM/PFM control improves

efficiency

● Quasi-resonant operation for highest overall efficiency

● Direct drive of low-cost BJT switch

● Dynamic base current control

● No external compensation components required

● Complies with EPA 2.0 energy-efficiency specifications

with ample margin

● Built-in short circuit protection and output overvoltage

protection

● Built-in current sense resistor short circuit protection

● Constant current control enables output current limit and

overload protection

● No audible noise over entire operating range

Figure 3.1: iW1706 Typical Application Circuit

2.0 Description

The iW1706 is a high performance AC/DC power supply

controller which uses digital control technology to build peak

current mode PWM flyback power supplies. The device

directly drives a power BJT and operates in quasi-resonant

mode to provide high efficiency along with a number of key

built-in protection features while minimizing the external

component count, simplifying EMI design and lowering the

total bill of material cost. The iW1706 features a distinctive

soft-start scheme, which allows for fast and yet smooth

start-up with both small and large capacitive loads. The

iW1706 removes the need for secondary feedback circuitry

while achieving excellent line and load regulation. It also

eliminates the need for loop compensation components

while maintaining stability over all operating conditions.

Pulse-by-pulse waveform analysis allows for a loop

response that is much faster than traditional solutions,

resulting in improved dynamic load response. The built-in

power limit function enables optimized transformer design

in universal off-line applications and allows for a wide input

voltage range.

iWatt’s innovative proprietary technology ensures that

power supplies built with the iW1706 can achieve both

highest average efficiency and fast yet smooth start-up with

a wide range of capacitive loads, and are ideal for network

power adapter applications.

3.0 Applications

● Network power adapters for ADSL, wireless access

points, routers.

L

+

GND

U1

iW1706

GND

OUTPUT

1

3

2

5

4

N

+