an1773

Application Note 1773
Author: Jun Liu
ISL78205EVAL2Z Evaluation Board Setup Procedure
The ISL78205EVAL2Z board is used to demonstrate the
compact size and operations of synchronous/asynchronous
buck using the ISL78205.
The ISL78205EVAL2Z board input voltage range is 3V to 40V.
The output voltage is set to 5V and can be changed by using
the voltage feedback resistors. Note that to change to a higher
output voltage, the output capacitors’ voltage ratings have to
be checked.
The board output current is 2A typical. The board is set at to a
default overcurrent threshold of 3.6A. The OC threshold can be
programmed by R15 at the ILIMIT pin.
The ISL78205EVAL2Z board has an optional diode D1 for
asynchronous buck configuration.
The board is set to a default frequency of 500kHz. The
frequency can be programmed by R8 at the FS pin.
The board can be synchronized to the external clock. Multiple
ISL78205EVAL2Z boards can be synchronized simply by
connecting their SYNC pins together.
Recommended Equipment
• 0V to 40V power supply with at least 3A source current
capability
• Load capable of sinking current up to 3A
• Multimeters
• Oscilloscope
Quick Startup
1. Connect the power source to the input terminals P1(VIN+)
and P2(GND). Connect the load terminals to the buck
outputs P3(VOUT+) and P4(GND). Make sure the setup is
correct prior to applying any power or load to the board.
2. Adjust the power source to 12V and turn it on.
3. Verify the output voltage is 5V and use the oscilloscope to
monitor the phase node waveforms through JP2.
Asynchronous Buck
Configuration
To configure the board to asynchronous buck, remove R19 and
change R20 (on bottom of the board) to 0Ω to ensure that Q1
is securely off.
FIGURE 1A. TOP
FIGURE 1B. BOTTOM
FIGURE 1. ISL78205EVAL2Z BOARD IMAGES
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Copyright Intersil Americas Inc. 2012. All Rights Reserved.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
Application Note 1773
TABLE 1. CONNECTORS/TEST POINTS DESCRIPTIONS
REF DES
NAME
DESCRIPTION
P1
VIN+
Positive terminal of buck inputs.
P2
GND
Ground terminal of buck inputs.
P3
VOUT+
Positive terminal of buck outputs.
P4
GND
Ground terminal of buck outputs.
TP1
VOUT+
TP2
GND
TP3
PGOOD
TP4
SYNC
TP5
VCC
Test point used to monitor VCC.
TP10
VIN+
Test point for VIN+.
TP11
GND
Ground test point used for monitoring inputs.
JP1
EN
JP2
PHASE
Test point for VOUT+.
Ground test point used for monitoring outputs.
Test point used to monitor PGOOD.
Used for synchronization configuration.
Option 1: to apply external clock for the IC to be synchronized with.
Option 2: to synchronize multiple ISL78205, simply connect those SYNC pins together.
Use this connector to control IC ON/OFF.
Test points used to monitor PHASE node waveforms. For monitoring purposes only. Do not short it with jumper.
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ISL78205EVAL2Z Board Schematic
8
7
6
5
4
3
2
1
D
D
TP10
VIN+
P1
BOOT
C22
0.1UF
U1
1UF
C3
ISL78205AVEZ
E
C12
10UF
C11
10UF
C10
TP2
PGOOD
R5
+5V/2A
TP3
E
P3
VOUT+
10UF
SQS462EN
D1
5
6
7
8
Q1
4
R20
5.1K
PDS360-13
0
1
2
3
R2
R19
E
10K
EPAD
VCC
COMP
FB
R15
FB
C8
E
10UH
OPEN
COMP
SS
0.015UF
C4
ILIMIT
FS
C
VOUT+
E
P4
GND
GND
B
C7
44.2K
R4
3.92K
330PF
R3
232K
E
A
A
DRAWN BY:
RELEASED BY:
UPDATED BY:
JUN LIU
TIM KLEMANN
DATE:
ENGINEER:
DATE:
TITLE:
02/14/2012
DATE:
03/01/2012
TESTER
JUN LIU
ISL78205
EVALUATION BOARD
SCHEMATIC
MASK#
FILENAME:
~/ISL78205/ISL78205EVAL2ZA
8
7
6
5
4
FIGURE 2. ISL78205EVAL2Z BOARD SCHEMATIC
3
2
DATE:
HRDWR ID
SHEET
REV.
1
1
OF
A
1
Application Note 1773
E
E
PHASE
PGOOD
DGND
EN
B
E
TP1
L1
OPEN
E
E
SS
D1 IS AN OPTIONAL DIODE FOR ASYNCHRONOUS BUCK CONFIGURATION
TP4
JP2
PHASE
PGOOD
NC
FS
R8
PHASE
VCC
4.7UF
OPEN
VIN
SGND
C1
EN
JP1
NC
10.2K
VCC
TP5
VIN
LGATE
SYNC
C9
E
GND
SYNC
150PF
GND
LGATE
BOOT
E
VIN+
TP11
E
E
P2
C
PGND
R7
C21
2.2UF
C20
2.2UF
3
VIN+
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Application Note 1773
Board Layouts
FIGURE 3. SILKSCREEN TOP COMPONENTS
FIGURE 4. TOP LAYER
FIGURE 5. 2 nd LAYER
FIGURE 6. 3 rd LAYER
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Application Note 1773
Board Layouts
(Continued)
FIGURE 7. BOTTOM LAYER
FIGURE 8. SILKSCREEN BOTTOM COMPONENTS
FIGURE 9. TOP COMPONENT ASSEMBLY
FIGURE 10. BOTTOM COMPONENT ASSEMBLY (MIRRORED)
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Application Note 1773
TABLE 2. BILL OF MATERIALS
REF DES
PART NUMBER
QTY
DESCRIPTION
MANUFACTURER
C3
C1608X7R1C105K
1
CAP, SMD, 0603, 1.0µF, 16V, 10%, X7R, ROHS
TDK
C10, C11, C12
C3216X7R1C106K
3
CAP, SMD, 1206, 10µF, 16V, 10%, X7R, ROHS
TDK
C1
GRM21BR71A475KA73L
1
CAP, SMD, 0805, 4.7µF, 10V, 10%, X7R, ROHS
MURATA
C20, C21
GRM31CR71H225KA88L
2
CAP, SMD, 1206, 2.2µF, 50V, 10%, X7R, ROHS
MURATA
C8
ECU-E1H151KBQ
1
CAP, SMD, 0402, 150pF, 50V, 10%, NP0, ROHS
PANASONIC
C4
VARIOUS
1
CAP, SMD, 0402, 0.015µF, 16V, 10%, X7R, ROHS
VARIOUS
C7
VARIOUS
1
CAP, SMD, 0402, 330pF, 50V, 10%, X7R, ROHS
VARIOUS
C9
N/A
0
CAP, SMD, 0402, DNP-PLACE-HOLDER, ROHS
N/A
C22
VARIOUS
1
CAP, SMD, 0603, 0.1µF, 50V, 10%, X7R, ROHS
VARIOUS
L1
SD8350-100-R
1
COIL-PWR INDUCTOR, SMD, 9.5X8.3, 10µH, 20%, 4A, 31.4mΩ, ROHS
COILTRONICS
D1
PDS360-13
1
DIODE-SCHOTTKY, SMD, POWERDI5, 60V, 3A, ROHS
DIODES INC.
U1
ISL78205AVEZ
1
IC-2.5A BUCK CONTROLLER, 20P, HTSSOP, ROHS
INTERSIL
Q1
SQS462EN
1
TRANSISTOR-MOS, N-CHANNEL, 8P, PWRPAK, 60V, 8A, ROHS
VISHAY
R19
VARIOUS
1
RES, SMD, 0402, 0Ω, 1/16W, 5%,ROHS
VARIOUS
R2
VARIOUS
1
RES, SMD, 0402, 10k, 1/16W, 1%, ROHS
VARIOUS
R7
VARIOUS
1
RES,SMD, 0402, 10.2k, 1/16W, 1%, ROHS
VARIOUS
R3
VARIOUS
1
RES, SMD, 0402, 232k, 1/16W, 1%, ROHS
VARIOUS
R5
VARIOUS
1
RES,SMD, 0402, 3.92k, 1/16W, 1%, ROHS
VARIOUS
R4
VARIOUS
1
RES, SMD ,0402, 44.2k, 1/16W, 1%, ROHS
VARIOUS
R20
VARIOUS
1
RES, SMD, 0402, 5.1k, 1/16W, 1%, ROHS
VARIOUS
R8, R15
N/A
0
RES, SMD, 0402, DNP-PLACE-HOLDER, ROHS
N/A
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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