iW1697
Low-Power Off-Line Digital Green-Mode PWM Controller
1.0 Features
2.0 Description
● Primary-side feedback eliminates opto-isolators and The iW1697 is a high performance AC/DC power supply
simplifies design
controller which uses digital control technology to build
peak current mode PWM flyback power supplies. The
device together with an external active device (depletion
mode NFET or NPN BJT) provides a fast start-up without
● No-load power consumption < 20 mW at 230 Vac with
typical application circuit (5 star rating)
● Active start-up scheme enables fastest possible start- compromising no-load power loss. The device directly
up
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
● Fast dynamic load response
● Adaptive multi-mode PWM/PFM control improves count, simplifying EMI design and lowering the total bill of
efficiency
material cost. The iW1697 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.
● Quasi-resonant operation for highest overall efficiency
● EZ-EMI ® design to easily meet global EMI standards
● Direct drive of low-cost BJT switch
● Dynamic base current control
● Very tight constant voltage and constant current
regulation with primary-side-only feedback
● No external compensation components required
iWatt’s innovative proprietary technology ensures that
power supplies built with iW1697 can achieve both highest
average efficiency and less than 20 mW no-load power
consumption, and have fast dynamic load response, all
with a typical application circuit. The active start-up scheme
enables shortest possible start-up time without sacrificing
no-load power loss.
● Complies with EPA 2.0 energy-efficiency specifications
with ample margin
● Ultra-low start-up current (1.5 μA typical)
● Built-in soft start
● Built-in short circuit protection and output overvoltage
protection
3.0 Applications
● Low power AC/DC adapter/chargers for cell phones,
● Built-in current sense resistor short circuit protection
● No audible noise over entire operating range
PDAs, digital still cameras
L
● Linear AC/DC replacement
V
OUT
+
+
GND
N
U1
iW1697
1
2
3
6
5
4
V
V
OUTPUT
GND
CC
SENSE
ASU
I
SENSE
Figure 3.1: iW1697 Typical Application Circuit
(Achieving < 20 mW No-load Power Consumption. Using Depletion Mode NFET as Active Start-up Device)
Rev. 1.1
iW1697
FebRuaRy 1, 2012
Page 1
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