an1388

ISL8009AEVAL1Z: 1.5A Synchronous Buck
Regulator with Integrated MOSFETs
®
Application Note
Description
October 9, 2008
AN1388.1
Quick Setup Guide
The ISL8009AEVAL1Z kit is intended for use by individuals
with requirements for Point-of-Load applications sourcing
from 2.7V to 5.5V. The ISL8009EVAL1Z evaluation board
demonstrates the performance of the ISL8009A low
quiescent current mode converter.
1. Ensure that the circuit is correctly connected to the supply
and loads prior to applying any power.
The ISL8009A is offered in a 2mmx3mm 8 Ld DFN package
with 1mm maximum height. The complete converter
occupies less than 1cm2 area.
4. Turn on the power supply.
Key Features
• High Efficiency Synchronous Buck Regulator With up to
95% Efficiency
2. Connect the bias supply to VIN. Plus terminal to P4(VIN)
and negative return to P5(GND).
3. Verify that position is ON for SW1.
5. Verify the output voltage is 1.8V for VOUT
Evaluating the Other Output Voltage
The ISL8009AEVALIZ kit output is preset to 1.8V; however,
output voltages can be adjusted from 0.8V to 3.3V by
following Equations 1 and 2:
R 1⎞
⎛
V OUT = 0.8 ⎜ 1 + -------⎟
R 2⎠
⎝
• 2ms Reset Timer
• Soft Discharge Output Cap During Disable
(EQ. 1)
Let’s set R1= 124kΩ:
• 2.7V to 5.5V Supply Voltage
• 1.5A Guaranteed Output Current
( R1 )
R 2 = ------------------------------V OUT
⎛ ----------------⎞ – 1
⎝ 0.8 ⎠
• 17µA Quiescent Supply Current in PFM Mode
If desired output is 0.8V then short R1 and open R2.
• Selectable Forced PWM Mode and PFM Mode
Mode Control
• Less Than 1µA Logic Controlled Shutdown Current
The ISL8009A has a SKIP pin that controls the operation
mode. When the SKIP pin is driven to low or shorted to
ground, the regulator operates in a forced PWM mode. The
forced PWM mode remains the fixed PWM frequency at light
load instead of entering the skip mode.
• 3% Output Accuracy Over-Temperature/Load/Line
• 90% Maximum Duty Cycle for Lowest Dropout
• Internal Current Mode Compensation
• Internal Digital Soft-Start
(EQ. 2)
TABLE 1. SWITCH 1 SETTINGS
• Peak Current Limiting, Short Circuit Protection
SW1
SKIP
1
PWM
Fixed PWM frequency at light load
3
PFM
Force continuous mode
SW2
ENABLE
Recommended Equipment
1
OFF
Disable VOUT
The following materials are recommended to perform
testing:
3
ON
Enable VOUT
• Over-Temperature Protection
• Enable
FUNCTION
• Small 8 Ld 2mmx3mm DFN
• Pb-Free (RoHS Compliant)
ON/OFF CONTROL
• 0V to 10V power supply with at least 5A source current
capability, battery, notebook AC adapter
• Two electronic loads capable of sinking current up to 5A
• Digital Multimeters (DMMs)
• 100MHz quad-trace oscilloscope
• Signal generator
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2008. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 1388
Schematic
1
J1
3
4
5 4 3
1
J2
2
VIN
1
1
C1
10µF
C2
10µF
2
2
1
2
3
4
EN
POR
SKIP
5
RSI 6
VFB
7
GND
LX 8
VIN
EN
POR
SKIP
E
ISL8009AIRZ-T
1
2
R1
124k
A
9
1
C4
220pF
P7
1
C5
10µF
C6
10µF
2
1
A
3
11
RSI
2
P8
2
2
1
P5
5
4
L1
2.2µH
9
1
P4
5 4 3
A
U1
A
R2
100k
A
1
A
11
P1
RSI
R3
100k
VIN
VIN
2
2
2
VIN
2
R6
100k
2
R5
2k
R7
100k
1
2
SKIP
3
SW2
1
2
21
2
2
R4
100k
PG
31
1
31
1
Q1
A
2
2
3
SW1
1
1
ON/EX
OFF
1
1
P6
2
R9
OPEN
R8
OPEN
OPEN
1
1
2
2
EN
PWM
2
2N7002
22
1
P2
D1
D
1
P3
1
1
PFM
1
A
A
A
AN1388.1
October 9, 2008
Application Note 1388
TABLE 2. COMPONENT LIST
REF
DES
QTY VALUE TOL. VOLTAGE
PACKAGE
PART NUMBER
MANUFACTURER
DESCRIPTION
C1, C2,
C5, C6
4
10µF
10%
10V
1206
GRM31CR71A106KA01L-T MURATA
CAP, SMD, 1206, 10µF, 10V, 10%,
X7R, ROHS, MONOLITHIC
C4
1
220pF
5%
50V
0603
H1045-00221-50V5-T
VENKEL
CAP, SMD, 0603, 220pF, 50V, 5%,
C0G, ROHS
L1
1
2.2µH
20%
7.6x6
DR73-2R2-R
COOPER
ELECTRONIC
TECH.
COIL-PWR INDUCTOR, SMD,
7.6x6, 2.2µH, 20%, 4.15A, ROHS
D1
1
LITEON/VISHAY
LED-GaAs RED, SMD,
2mmx1.25mm, 100mW, 40mA,
10mcd, ROHS
U1
1
Q1
1
R2-R4,
R6, R7
5
R1
2mmx1.25mm LTST-C170CKT
2x3
ISL8009AIRZ
INTERSIL
IC-1.5A SYNC BUCK REGULATOR,
8P, DFN, 2x3, ROHS
2N7002-7-F-T
DIODES, INC.
TRANSISTOR, N-CHANNEL, 3 LD
SOT-23, 60V, 115mA, ROHS
-
60V
N-CHANNEL
100k
1%
100V
0603
H2511-01003-1/10W1-T
1
124k
1%
100V
0603
H2511-01243-1/10W1-T
YAGEO
RES, SMD, 0603, 124k,1/10W,1%,
TF, ROHS
R5
1
2k
1%
100V
0603
H2511-02001-1/10W1-T
KOA
RES, SMD, 0603, 2k, 1/10W, 1%,
TF, ROHS
R8, R9
0
100V
0603
H2511-DNP
SW1,
SW2
2
-
-
-
-
3
GT11MSCBE-T
RES, SMD, 0603, 100k, 1/10W, 1%,
TF, ROHS
RES, SMD, 0603, DNP-PLACE
HOLDER, ROHS
C&K
COMPONENTS
SWITCH-TOGGLE, SMD,
ULTRAMINI, 1P, SPST MINI
AN1388.1
October 9, 2008
Application Note 1388
ISL8009AEVAL1Z Board Layout
FIGURE 1. TOP COMPONENTS
FIGURE 2. TOP LAYER ETCH
4
AN1388.1
October 9, 2008
Application Note 1388
ISL8009AEVAL1Z Board Layout
(Continued)
FIGURE 3. BOTTOM LAYER COMPONENTS (MIRRORED)
FIGURE 4. BOTTOM LAYER ETCH (MIRRORED)
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
5
AN1388.1
October 9, 2008
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