an1766

Application Note 1766
Author: Jun Liu
ISL85402EVAL2Z Evaluation Board Setup Procedure
Recommended Equipment
The ISL85402EVAL2Z board is used to demonstrate the
compact size and operations of synchronous buck using
ISL85402.
The ISL85402 supports an input voltage range of 3V to 36V.
Note that the input voltage of this board is limited by the input
capacitor C2(25V rating). When an input voltage higher than
20V is desired, replace C2 with capacitors with higher voltage
ratings.
The output voltage is set to 5V and can be changed by voltage
feedback resistors. Note that in order 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 to a
default overcurrent threshold of 3.6A. the OC threshold can be
programmed by a resistor at the ILIMIT pin.
The ISL85402EVAL2Z board has configuration options of
forced PWM mode or PFM mode.
• 0V to 36V power supply with at least 5A source current
capability
• Load capable of sinking current up to 3A
• Multimeters
• Oscilloscope
Quick Startup
1. Connect test point MODE to ground when forced PWM
mode (no PFM) is desired; leave MODE floating if PFM
mode is desired.
2. Connect the power source to the input terminals VIN+ and
VIN-. Connect the load terminals to the buck outputs VO+
and VO-. Make sure the setup is correct prior to applying any
power or load to the board.
3. Adjust the power source to 12V and turn it on.
4. Verify the output voltage is 5V and use oscilloscope to
monitor the phase node waveforms.
The board is set to a default frequency of 500kHz. The
frequency can be programmed by a resistor at R1.
The board can be synchronized to external clock. Multiple
ISL85402EVAL2Z boards can be synchronized simply by
connecting their SYNC pins together.
0.9’’
0.39’’
BOTTOM
TOP
FIGURE 1. ISL85402EVAL2Z BOARD IMAGE
July 26, 2012
AN1766.1
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas Inc. 2012. All Rights Reserved
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 1766
TABLE 1. CONNECTORS/TEST POINTS DESCRIPTIONS
TEST POINT
DESCRIPTION
VIN+
Positive terminal of buck inputs.
VIN-
Ground terminal of buck inputs.
VO+
Positive terminal of buck outputs.
VO-
Ground terminal of buck outputs.
VCC
Test point to monitor the VCC.
EN
Use this connector to control IC ON/OFF.
ILIMIT
Use it to set up the overcurrent limit threshold. With the ILIMIT pin connected to VCC or GND, or left open, the IC has a default 3.6A
OC threshold. The OC threshold can be programmed by a resistor from the ILIMIT pin to ground.
MODE
Mode setup connector. Connecting the MODE pin to GND will set the IC in forced PWM mode; leaving the MODE pin open or
connected to VCC will set the IC to have PFM available under light load conditions. The IC’s default PFM current threshold is 0.7A.
R16 is a placeholder for a resistor to program the PFM current threshold.
PGOOD
Test point to monitor PGOOD.
SYNC
Used for synchronization configuration.
Option 1: to apply external clock for the IC to be synchronized with.
Option 2: to synchronize multiple ISL85402s, simply connect the SYNC pins together.
2
AN1766.1
July 26, 2012
ISL85402EVAL2Z Board Schematic
VIN+
E
C1
4.7UF
VCC
E
C2
VO+
COMP
16
18
17
VIN
VIN
19
VCC
SGND
12
EXT
BOOST
SYNC
11
E
C3
PHASE
PHASE
ISL85402IRZ
PGOOD
EP
13
SYNC
10
9
PGOOD
8
6
ILIMIT
7
E
E
C8
R2
C10
3.92K
150PF
R4
R3
44.2K
232K
1
8
2
7
3
6
4
5
BSZ100N06LS3G
FIGURE 2. ISL85402EVAL2Z BOARD SCHEMATIC
VO+
10UH
Q1
E
1000PF
VO+
L1
C6
5
14
LGATE
10UF
FB
15
C5
4
U1
BOOT
PGND
10UF
SS
E
1UF
FS
3
MODE
10PF
2K
EN
2
21
C9
C7
100PF
R7
C4
E
1
VIN-
+5V/2A
VO-
E
Application Note 1766
0.015UF
E
DNP
EN
ILIMIT
MODE
3
R1
AUXVCC
20
10UF
AN1766.1
July 26, 2012
Application Note 1766
TABLE 1. BILL OF MATERIALS
REF DES
PART NUMBER
QTY
DESCRIPTION
MANUFACTURER
C9
C0402COG500-100JNE
1
CAP, SMD, 0402, 10pF, 50V, 5%, NP0, ROHS
VENKEL
C7
VARIOUS
1
CAP, SMD, 0402, 100pF, 25V, 10%, C0G, ROHS
VARIOUS
C3
ECJ-OEB0J105M
1
CAP, SMD, 0402, 1µF, 6.3V, 20%, X5R, ROHS
PANASONIC
C10
VARIOUS
1
CAP, SMD, 0402, 150pF, 50V, 5%, NP0, ROHS
VARIOUS
C4
VARIOUS
1
CAP, SMD, 0402, 0.015µF, 16V, 10%, X7R, ROHS
VARIOUS
C8
VARIOUS
1
CAP, SMD, 0402, 1nF, 25V, 10%, X7R, ROHS
VARIOUS
C5,C6
VARIOUS
2
CAP, SMD, 0805, 10µF, 6.3V, 10%, X5R, ROHS
VARIOUS
C1
0805ZD475KAT2A
1
CAP, SMD, 0805, 4.7µF, 10V, 10%, X5R, ROHS
AVX
C2
TMK316B7106KL-TD
1
CAP, SMD, 1206, 10µF, 25V, 10%, X7R, ROHS
TAIYO YUDEN
L1
SD8350-100-R
1
COIL-PWR INDUCTOR, SMD, 9.5X8.3, 10µH, 20%, 4A, 31.4mΩ, ROHS
COILTRONICS
U1
ISL85402IRZ
1
IC-SWITCHING REGULATOR, 20P, QFN, 4X4, ROHS
Q1
BSZ100N06LS3G
1
TRANSIST-MOS, N-CHANNEL, 8P, PG-TSDSON-8, 60V, 20A, ROHS
R2
VARIOUS
1
RES, SMD, 0402, 3.92k, 1/16W, 1%, TF, ROHS
VARIOUS
R3
VARIOUS
1
RES, SMD, 0402, 232k, 1/16W, 1%, TF, ROHS
VARIOUS
R7
VARIOUS
1
RES, SMD, 0402, 2k, 1/16W, 1%, TF, ROHS
VARIOUS
R4
ERJ-2RKF4422X
1
RES, SMD, 0402, 44.2k, 1/16W, 1%, TF, ROHS
VARIOUS
R1
N/A
0
RES, SMD, 0402, DNP, DNP, DNP, TF, ROHS
4
INTERSIL
INFINEON TECHNOLOGY
N/A
AN1766.1
July 26, 2012
Application Note 1766
Board Layouts
FIGURE 3. SILKSCREEN TOP COMPONENTS
FIGURE 4. TOP LAYER
FIGURE 5. 2 nd LAYER
FIGURE 6. 3 rd LAYER
FIGURE 7. BOTTOM LAYER
FIGURE 8. SILKSCREEN BOTTOM COMPONENTS
5
AN1766.1
July 26, 2012
Application Note 1766
Board Layouts
(Continued)
FIGURE 9. TOP COMPONENT ASSEMBLY
FIGURE 10. BOTTOM COMPONENT ASSEMBLY (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
6
AN1766.1
July 26, 2012
Similar pages