ISL6529EVAL1 User Guide

ISL6529EVAL1 - Synchronous Buck and
Linear Controller
®
Application Note
October 14, 2005
AN1134.0
Author: Hal Wittlinger
Introduction
5VCC
Customer demands for higher levels of graphic performance
are also driving Accelerated Graphics Port (AGP) initiatives
to higher performance levels. This upward performance
spiral places greater demands on bus speeds and data rates
that in turn place greater demands on the system power
supplies.
SOFT-START
FAULT LOGIC
1.28V
0.41V
0.80V
VOLTAGE
REFERENCE
The ISL6529 addresses these needs by providing two
independent voltage programmable regulators. One
regulator is a high current synchronous buck converter
topology and the other is a linear regulator.
Figure 1 shows the Evaluation Board. Power is supplied to
the board via the ATX connector. Switch SW1 to the right of
the ATX connector controls the ATX power supply. When the
switch is in the upward position towards the PC board SW1
label, the ATX supply is activated.
12VCC
POWER-ON
RESET (POR)
UGATE
GATE
LOGIC
+
UV
-
+
UV
FB2
LGATE
-
DRIVE2
OSCILLATOR
+
E/A
+
SHUT
DOWN
E/A
+
FB
COMP
PWM
+
GND
FIGURE 2. ISL6529 BASIC BLOCK DIAGRAM
A simple block diagram of the ISL6529 is shown in Figure 2.
Integrated high-bandwidth error amplifiers and an accurate
internal voltage reference insures static voltage regulation of
±2% for the ISL6529C and ±1% for the ISL6529AC over line,
load and temperature ranges. Simple undervoltage (UV)
comparators monitor the FB lines of each regulator and
shut down both outputs when a fault is detected on either FB
input. For a more detailed description of the ISL6529
functionality, refer to the ISL6529 Data Sheet [1].
The ISL6529EVAL1 Reference Design
FIGURE 1. ISL6529 EVALUATION BOARD
Intersil ISL6529
The ISL6529 regulates two output voltages and provides
simple protection functions for both outputs. The integrated
PWM controller drives two external N-Channel MOSFET
transistors in a synchronous buck converter topology. This
regulator is intended to support GPUs or embedded
processor loads. The integrated linear controller drives an
external N-Channel MOSFET pass transistor in a standard
linear regulator configuration, typically regulating the local
memory voltage bus required by most GPUs or embedded
processors
1
The ISL6529EVAL1 evaluation board is intended to provide
a versatile platform for evaluation of this device with surface
mount components. The synchronous buck converter is
capable of 6A continuous load current and handling 2.5A/µs
load current transients. The linear regulator is designed to
supply 1A of continuous load current and transient currents
up to 3A. A LED power-on indicator is illuminated when the
board is power by the ATX supply. The board is implemented
with a 2-ounce copper on a 2-layer, printed circuit board.
See page 6 for layout plots.
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Application Note 1134
Quick Start Evaluation
5V ATX SUPPLY
Circuit Setup
12V ATX SUPPLY
The ISL6529EVAL1 does not require any jumper settings
and a simple on-board switch toggles the ATX PS_ON#
power-on control input. Make sure the on-board ATX switch,
SW1, is pointed toward the bottom of the PC board. This will
keep the ATX supply off while connections are made to
critical test points. Remember that the ATX +5VDC output
and the +3.3VDC output must be loaded to at least 0.3A to
insure that all ATX outputs are within specifications.
VOUT2
VOUT1
Input Power Connections
The 20-pin ATX header, J1, mates with a standard ATX
power supply connector. Place the ATX switch towards the
lower portion of the board to insure that no inadvertent
connections cause damage to the board while mating the
connector to the board. Toggle the ATX switch towards the
SW1 label on the top of the board to release the PS_ON#
input to the ATX supply and power the evaluation board.
Once the ATX outputs are up, the red LED indicator, LP1,
will begin illuminating when the ATX PWR_OK output
transitions high.
If regular bench supplies are used, an ATX extension cable
can be modified by paralleling and bringing out all the
grounds, 3.3V, 5V and the single 12V line. It is important to
make sure all lines are connected. Note that SW1 will not
inhibit operation and LP1 will not be illuminated when using
bench supplies.
The two regulator outputs can be exercised using either
resistive or electronic loads. Connections for the
synchronous buck converter output are twin posts, TP1 and
TP2, labeled VOUT1 and GND respectively. A shielded
scope probe test point, TP3, between TP1 and TP2 allows
for accurate observation of the output voltage with minimum
of extraneous pick-up from switching signals. The linear
regulator output posts, TP4 and TP5, are labeled VOUT2
and GND. An additional ground post, TP6 is located next to
the power indicator lamp, LP.
ISL6529EVAL1 Performance
Soft-Start Interval
Powered by a standard ATX power supply, Figure 3 shows
the controlled start-up of both regulators on the
ISL6529EVAL1. The soft-start interval begins when the
voltage applied to 5V VCC increases beyond the power-on
reset rising threshold of 4.4V typically and the 12V input is
above typically 10.4V. During the soft-start interval both
outputs slowly ramp up to their proper voltage levels. VOUT1
begins normal regulation at 1.6V and VOUT2 at 2.57V. The
soft-start interval lasts about 3ms. This controlled ramping of
both output voltages and supply currents reduces the stress
on the systems powered by these regulators and the ATX
supply.
2
FIGURE 3. SOFT-START WAVEFORMS
Transient Response
The expected GPU transient slew rate of 2.5A/µs allows
the ISL6529 synchronous buck converter to support loads
up to 6A.
The leading edge transient response of the ISL6529 EVAL1
board is captured in Figure 4.
VOUT1 SWITCHING REGULATOR - 200mV/DIV
VOUT2 LINEAR REGULATOR - 200mV/DIV
LOAD CURRENT - 5A/DIV
UPPER GATE DRIVE - 10V/DIV
FIGURE 4. SWITCHING REGULATOR RESPONSE TO 6A
TRANSIENT LOADING
The core voltage immediately drops when the transient is
applied as the bulk and ceramic output capacitors begin to
support the output voltage. The controller detects the new
load level by the drop in output voltage and responds by
pushing the PWM output to maximum duty cycle. Note on
the falling edge as the load is removed the PWM output
goes to minimum duty cycle until the output voltage drops to
the defined regulated voltage, where the PWM resumes
normal operation.
AN1134.0
October 14, 2005
Application Note 1134
Figure 5 shows similar response by the linear regulator.
Notice that both regulators are conservatively compensated
at the cost of slower transient response. Refer to the
ISL6529 data sheet for techniques to optimize regulator
response.
Efficiency
The performance of the ISL6529EVAL1 board loaded from
1A to 6A is plotted in Figure 7. The measurements were
made at thermal equilibrium under room temperature
conditions with no air flow.
INPUT VOLTAGE = 3.3V
90
VOUT1 SWITCHING REGULATOR - 200mV/DIV
VOUT1 = 2.5V
VOUT1 = 1.6V
80
EFFICIENCY (%)
VOUT2 LINEAR REGULATOR - 200mV/DIV
LOAD CURRENT - 5A/DIV
UPPER GATE DRIVE - 10V/DIV
70
VOUT1 = 0.8V
60
FIGURE 5. LINEAR REGULATOR RESPONSE TO 3A
TRANSIENT LOADING
Undervoltage Protection
The ISL6529 monitors the feedback voltage on both FB pins
to detect if either output is less than 52.5% of the reference
voltage. This feature provides simple short circuit protection
of both outputs. If one output voltage does drop below the
UV threshold, then both outputs are quickly shut down. The
outputs are held low for a set delay interval of about 10.5ms
and then a normal soft-start interval is attempted. The UV
protection circuitry becomes active 1ms into the new softstart interval and if the output does not rise above the UV
threshold, then both outputs are again shut down. This
hiccup mode cycle is repeated until both outputs soft-start
normally or power to the controller is removed.
Figure 6 shows this operation of the converter when a hard
short is applied across the output terminals of VOUT1. Both
outputs are quickly shut down and three separate soft-start
intervals are attempted after brief delay intervals.
50
0
1
2
3
4
LOAD CURRENT (A)
5
6
FIGURE 7. EFFICIENCY vs LOAD CURRENT FOR 3 OUTPUT
VOLTAGES
Summary
The ISL6529EVAL1 is an adaptable evaluating tool which
showcases the performance of the ISL6529C and
ISL6529AC. Designed to meet the performance
requirements of Graphics Card applications, it allows the
user the flexibility to configure it for future designs as well.
The following pages provide a schematic of the board, bill of
materials, and layout drawings to support implementation of
this solution.
References
Intersil documents are available on the web at
http://www.intersil.com.
[1] ISL6529 Data Sheet, Intersil Corporation, File No.
FN9070.
VOUT1, 0.5V/DIV
VOUT2, 0.5V/DIV
0 VOLTS
VOUT1, LOAD 5A/DIV
0 VOLTS
DRIVE1, 10V/DIV
FIGURE 6. UNDERVOLTAGE PROTECTION
3
AN1134.0
October 14, 2005
Application Note 1134
L2
+3.3V
1µH
C7
1000µF
R9
+12V
+5V
C8
4.7µF
C6
470µF
2.7Ω
C15
1µF
C5
1µF
4
DRIVE1
12VCC
5VCC
UGATE 14
DRIVE2
5
TP8 R11
DRIVE2
0Ω
C4
TP7
1
LGATE
470pF
ISL6529
COMP
R12
COMP 10
6.8kΩ
6
9 TP9
FB2
FB
GND
PGND
R6
2
3
2.1kΩ
TP6
GND
R13
Q3
1.0kΩ
4.64kΩ
C12
1500µF
+3.3V
+5V
+12V
12
11
1
2
14
13
3
4
15
5
16
6
17
19
20
18
8
R8
L1
TP10
2.2Ω
C11
C1
47nF
R2
10.7kΩ
TP3
D1
2.2nF
C9
470µF
VOUT1
(6A)
TP1
1.6V
4.7µH
R10
C10
1µF
TP2
C2
1.2nF
R4
1.0kΩ
J1
9
C14
1µF
10
TP5
R5
7
VOUT2
(1A)
TP4
2.57V
Q1
13
R1
1.0kΩ
R3
10Ω
C3
47nF
R7
24Ω
SW1
C13
0.1µF
750Ω
ATX CONNECTOR
FIGURE 8. SCHEMATIC DIAGRAM OF ISL6529EVAL1 BOARD
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AN1134.0
October 14, 2005
Application Note 1134
ISL6529EVAL1 Bill of Materials
QTY
REFERENCE
DESCRIPTION
PACKAGE
VENDOR
PART NO.
2
C1, C3
47nF ±5%, 25V, X7R, Ceramic Capacitor
0603
Various
1
C2
1.2nF ±5%, 25V, X7R, Ceramic Capacitor
0603
Various
1
C4
470pF ±5%, 25V, X7R, Ceramic Capacitor
0603
Various
4
C5, C10, C14, C15
1µF, 25V, X5R, Ceramic Capacitor
0805
Various
2
C6, C9
470µF, 6.3V, Organic Capacitor
SM
Sanyo
SVP Series 6SVP470MX
1
C7
1000µF, 6.3V, Aluminum Capacitor
SM
Sanyo
6.3CV1000AX
1
C8
4.7µF, 16V, Y5V, Ceramic Capacitor
1206
Various
1
C11
2.2nF, 25V, X7R, Ceramic Capacitor
603
Various
1
C12
1500µF, 6.3V, Aluminum Capacitor
SM
Sanyo
1
C13
0.1µF, 25V, X5R, Ceramic Capacitor
1
D1
Schottky Rectifier
1
J1
ATX Power Header
1
L1
4.7µH, 5.2A Inductor
1
L2
1
6.3CV1500AX
Various
ON
MBRS1100T3
Molex
Jameco
39-29-9203
147379
SMT
TOKO
919AS-4R7M=P3
1.0µH, 9.7A Inductor
SMT
TOKO
919AS-1R0N=P3
LP1
Miniature LED, Through-Board Indicator
SM
Chicago Lamp, Inc. CMD91-21SRC/TR10
1
Q1
Dual N-Channel MOSFET Transistors
SO-8
IR
IRF7313
1
Q3
N-Channel MOS Transistor
D-PAK
ON
MTD3055VL
2
R1. R4
Resistor, 1.0kΩ, 1%, 1/10Ω
0603
Various
1
R2
Resistor, 10.7kΩ, 1%, 1/10W
0603
Various
1
R3
Resistor, 10Ω, 5%, 1/10W
0603
Various
1
R5
Resistor, 4.64kΩ, 1%, 1/10W
0603
Various
1
R6
Resistor, 2.1kΩ, 1%, 1/10W
0603
Various
1
R7
Resistor, 24Ω, 5%, 1/10W
0603
Various
1
R8
Resistor, 750Ω, 5%, 1/10W
0603
Various
1
R9
Resistor, 2.7Ω, 5%, 1/10W
0603
Various
1
R10
Resistor, 2.2Ω, 5%, 1/10W
0603
Various
1
R11
Resistor, 0Ω, 5%, 1/10W
0603
Various
1
R12
Resistor, 6.8kΩ, 1%, 1/10W
0603
Various
1
R13
Resistor, 1.0kΩ, 5%, 1/10Ω
0603
Various
1
SW1
Switch, DPST
SMT
CK
GT11MSCK
Thru Hole
Keystone
1514-2
Probe Socket
Thru Hole
Tektronics
131-4353-00
Small Test Point
Thru Hole
Jolo
SPCJ-123-01
Dual Regulator Controller
SO-8
Intersil
ISL6529CB
2 Layers
2 Oz Copper Various
5
TP1, TP2, TP4, TP5, TP6 Large Test Points
1
TP3
4
TP7, TP8, TP9, TP10
1
U1
1
PC Board
5
SMA
AN1134.0
October 14, 2005
Application Note 1134
ISL6529EVAL1 Evaluation Board Layout
FIGURE 1. TOP SILK SCREEN
FIGURE 2. TOP LAYER
FIGURE 3. BOTTOM LAYER
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
6
AN1134.0
October 14, 2005