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PDF IW1698 Data sheet ( Hoja de datos )
| Número de pieza | IW1698 | |
| Descripción | Low-Power Off-line Digital Green-Mode PWM Controller | |
| Fabricantes | iWatt | |
| Logotipo |  |
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iW1698
Low-Power Off-line Digital Green-Mode PWM Controller
1.0 Features
●● Primary-side feedback eliminates opto-isolators and
simplifies design
●● No-load power consumption < 30 mW at 230 Vac with
typical application circuit (5 star rating)
●● Adaptive multi-mode PWM/PFM control improves
efficiency
●● 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
●● Complies with EPA 2.0 energy-efficiency specifications
with ample margin
●● Low start-up current (8 μA typical)
●● Built-in soft start
●● Built-in short circuit protection and output overvoltage
protection
●● Built-in current sense resistor short circuit protection
●● No audible noise over entire operating range
2.0 Description
The iW1698 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 iW1698 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 iW1698 can achieve both highest average
efficiency and less than 30 mW no-load power consumption
with typical application circuit.
3.0 Applications
●● Low power AC/DC adapter/chargers for cell phones,
PDAs, digital still cameras
●● Linear AC/DC replacement
L
+
N
+ VOUT
GND
U1
iW1698
1 VCC
OUTPUT 5
2 GND
3 VSENSE
ISENSE 4
Rev. 1.2
Figure 3.1: iW1698 Typical Application Circuit (Achieving < 30 mW No-load Power Consumption)
iW1698
February 6, 2012
Page 1
1 page  
iW1698
Low-Power Off-line Digital Green-Mode PWM Controller
8.0 Functional Block Diagram
ENABLE
Start-up
VSENSE 3
Signal
VFB
Conditioning
Digital
Logic
Control
GND 2
VSENSE(NOM)
= 1.538 V
DAC
OCP
IPK
VIPK
1 VCC
BJT
Base
Drive
5 Output
1.1 V
4 ISENSE
Figure 8.1: iW1698 Functional Block Diagram
9.0 Theory of Operation
The iW1698 is a digital controller which uses a new,
proprietary primary-side control technology to eliminate the
opto-isolated feedback and secondary regulation circuits
required in traditional designs. This results in a low-cost
solution for low power AC/DC adapters. The core PWM
processor uses fixed-frequency Discontinuous Conduction
Mode (DCM) operation at higher power levels and switches
to variable frequency operation at light loads to maximize
efficiency. Furthermore, iWatt’s digital control technology
enables fast dynamic response, tight output regulation, and
full featured circuit protection with primary-side control.
Referring to the block diagram in Figure 8.1, the digital logic
control block generates the switching on-time and off-time
information based on the output voltage and current feedback
signal and provides commands to dynamically control the
external BJT base current. The system loop is automatically
compensated internally by a digital error amplifier. Adequate
system phase margin and gain margin are guaranteed by
design and no external analog components are required for
loop compensation. The iW1698 uses an advanced digital
control algorithm to reduce system design time and increase
reliability.
Furthermore, accurate secondary constant-current operation
is achieved without the need for any secondary-side sense
and control circuits.
The iW1698 uses adaptive multi-mode PWM/PFM control
to dynamically change the BJT switching frequency for
efficiency, EMI, and power consumption optimization. In
addition, it achieves unique BJT quasi-resonant switching to
further improve efficiency and reduce EMI. Built-in protection
features include overvoltage protection (OVP), output short
circuit protection (SCP), over current protection (OCP),
single point fault protection and ISENSE fault detection.
iWatt’s digital control scheme is specifically designed to
address the challenges and trade-offs of power conversion
design. This innovative technology is ideal for balancing new
regulatory requirements for green mode operation with more
practical design considerations such as lowest possible cost,
smallest size and high performance output control.
Rev. 1.2
iW1698
February 6, 2012
Page 5
5 Page 
iW1698
Low-Power Off-line Digital Green-Mode PWM Controller
About iWatt
iWatt Inc. is a fabless semiconductor company that develops intelligent power management ICs for computer, communication,
and consumer markets. The company’s patented pulseTrain™ technology, the industry’s first truly digital approach to power
system regulation, is revolutionizing power supply design.
Trademark Information
© 2012 iWatt, Inc. All rights reserved. iWatt, EZ-EMI and pulseTrain are trademarks of iWatt, Inc. All other trademarks and
registered trademarks are the property of their respective companies.
Contact Information
Web: http://www.iwatt.com
E-mail: [email protected]
Phone: 408-374-4200
Fax: 408-341-0455
iWatt Inc.
675 Campbell Technology Parkway, Suite 150
Campbell, CA 95008
Disclaimer
iWatt reserves the right to make changes to its products and to discontinue products without notice. The applications
information, schematic diagrams, and other reference information included herein is provided as a design aid only and are
therefore provided as-is. iWatt makes no warranties with respect to this information and disclaims any implied warranties of
merchantability or non-infringement of third-party intellectual property rights.
iWatt cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an iWatt product. No
circuit patent licenses are implied.
Certain applications using semiconductor products may involve potential risks of death, personal injury, or severe property
or environmental damage (“Critical Applications”).
iWatt SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED, OR WARRANTED TO
BE SUITABLE FOR USE IN LIFE‑SUPPORT APPLICATIONS, DEVICES OR SYSTEMS, OR OTHER CRITICAL
APPLICATIONS.
Inclusion of iWatt products in critical applications is understood to be fully at the risk of the customer. Questions concerning
potential risk applications should be directed to iWatt, Inc.
iWatt semiconductors are typically used in power supplies in which high voltages are present during operation. High-voltage
safety precautions should be observed in design and operation to minimize the chance of injury.
Rev. 1.2
iW1698
February 6, 2012
Page 11
11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet IW1698.PDF ] | |
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