ISL6721EVAL3Z Intersil, ISL6721EVAL3Z Datasheet

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ISL6721EVAL3Z

Manufacturer Part Number
ISL6721EVAL3Z
Description
EVAL BOARD 3 FOR ISL6721
Manufacturer
Intersil
Datasheets

Specifications of ISL6721EVAL3Z

Lead Free Status / RoHS Status
Lead free / RoHS Compliant
ISL6721EVAL3Z: Resonant Reset Forward
Converters for Low Power Applications
Abstract
Low cost, isolated power supplies with multiple outputs
are common in many applications such as automotive,
security monitoring, telecom, medical instruments, etc.
For these applications, multiple output rails are needed
for integrated circuits (IC) with different operation
voltages on the same printed circuit board (PCB). Usually
the voltage regulation of these outputs are not tight, and
the current level not high. Isolation between the
converter’s input and output is necessary for safety
considerations and ground separation. Isolated power
converters with multiple secondary side windings provide
low cost solutions for these applications. Intersil’s
isolated power family products support these applications
with both double-ended PWM controllers (ISL6740,
ISL67401, ISL6742, ISL6743, ISL6745), and single-
ended PWM controllers (ISL6840, ISL6841, ISL6842,
ISL6843, ISL6844, ISL6845, ISL6721, ISL6722, and
ISL6723). Single-ended flyback and forward converters
based on ISL6721 are the most frequently used because
of its high performance and low cost.
The ISL6721EVAL3Z board serves as a reference design
for single switch resonant reset forward converter with
multiple outputs for typical industry applications that
need isolation. It can be used for security monitoring
systems where an input voltage range of 21.6V to 52.8V
is typical for operation from a battery source of 24V or
48V with 10% tolerance.
FIGURE 1. TOP AND BOTTOM VIEW OF THE PCB BOARD
September 2, 2009
AN1491.0
1
1-888-INTERSIL or 1-888-468-3774
Application Note 1491
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Design Specifications
The evaluation board ISL6721EVAL3Z aims at the
following design specifications.
• Switching Frequency, . . . . . . . . . . . Fsw: 300kHz
• Input Voltage Range, V
• Output Voltage 1, V
• Output Current 1, I
• Output Voltage 2, V
• Output Current 2, I
• Overall Output Power, P
• Full Load Efficiency: 80% under all Line and Load
• Output Voltage Ripple: 50mV
• Minimum Load: 25% on 12V Rail, 20% on 18V
Description of Circuit Operation
The ISL6721 is a high performance single-ended PWM
controller intended for various isolated and non-isolated
applications for telecom power supply, server power and
industrial power supply. It can be used in various single
transistor topologies including forward and flyback
regulators, boost converters, buck-boost converters, and
SEPIC converters. With the rich protection and control
features, it provides optimal solutions for single ended
current mode PWM controlled isolated power converters
with minimum external components and high
performance.
A single switch forward topology has higher efficiency
over the cheap flyback converters, and is widely
accepted for less than 100W applications. However, the
forward transformer needs to be reset within each
switching cycle. There are mainly three reset methods,
that is, reset winding plus diode, active clamp switch,
and resonant reset with capacitor. In a resonant reset
converter (RRF), a reset capacitor is connected to the
drain source of the transistor. As the main switch is
turned off, a resonance is developed between the
magnetizing/leakage inductance and the equivalent
resonant capacitor. The high voltage across the drain of
the switch resets the core of the transformer. Only one
switch is used, and it does not need a reset winding or
diode.
Regulation
Regulation
Conditions
Output.
All other trademarks mentioned are the property of their respective owners.
|
Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2009. All Rights Reserved
OUT1
OUT2
OUT1
OUT2
IN
OUT
: 2.5A
: 1A
: 12V with 5% Absolute
: 18V with 5% Absolute
: 21.6V DC to52.8V DC
: 48W
P-P
on each Rail

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ISL6721EVAL3Z Summary of contents

Page 1

... ISL6723). Single-ended flyback and forward converters based on ISL6721 are the most frequently used because of its high performance and low cost. The ISL6721EVAL3Z board serves as a reference design for single switch resonant reset forward converter with multiple outputs for typical industry applications that need isolation ...

Page 2

VIN*NS/ FIGURE 2. EQUIVALENT CIRCUIT SCHEMATIC OF A RESONANT RESET CONVERTER WITH TRANSFORMER Figure 2 shows the simplified schematic of the resonant reset forward converter. The reset capacitance is formed by the drain source of the ...

Page 3

Equation 4. • • max sw • 21.6 0.4 N min p ------------------------------------------------------ - ---------------------------------------------------- - = ...

Page 4

I inRMS ( tr max • • • ----------------------------- - ------------------ - max max ( ) ×10 2. • • ×10 • ---------- - 300 --------------------------------------- ...

Page 5

TABLE 1. POWER LOSS ANALYSIS POWER DISSIPATED DEVICE Transformer Rectifiers Primary MOSFET Chokes Snubber Fixed Control Estimate Capacitors and CST Total Loss Estimate Feedback, OCP and Slope Compensation Slope compensation is a technique to add additional slope to the current ...

Page 6

Typical Performance Characteristics The major performance will be examined in terms of efficiency, and load/line regulation, and shown in Tables 2 through 4 for input voltages V = 22V, 34V and 52.8V, IN respectively. The performance closely matches the design ...

Page 7

... FIGURE 8. DRAIN SOURCE VOLTAGE FOR V FIGURE 9. DRAIN-SOURCE VOLTAGE FOR V = 2A, OUT1 Reference: ISL6721 datasheet FN9110, Intersil Corporation ISL6745 datasheet FN9161, Intersil Corporation IN ILOAD12V = 0.5A, ILOAD18V = 0.5A IN ILOAD12V = 0.5A, ILOAD18V = 0.5A IN ILOAD12V = 2A, ILOAD18V = 1A = 25V, = 50V, = 32V, AN1491.0 ...

Page 8

Schematic of ISL6721EVAL3 R5 R6 ...

Page 9

... Application Note 1491 TABLE 5. BILL OF MATERIALS REFERENCE DESIGNATOR DESCRIPTION PWB-PCB, ISL6721EVAL3Z, REVA, ROHS C19 RADIAL, 10x23, 1800µF, 16V, 20%, 12mW, ALUM. ELEC., ROHS C15 CAP, RADIAL, 10x20mm, 330µF, 35V, 20%, ALUM. ELEC., ROHS C16 CAP, SMD, 1210, 22µF, 16V,2 0%, X7R, ROHS C14 CAP, SMD, 1210, 10µ ...

Page 10

... Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com ...

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