AN1732 - Intersil

Application Note 1732
Author: Steve Schulte
ISL70002SEH 12A Synchronous Buck Regulator
Evaluation Board User Guide
Circuit Comments
Schematic and BOM
The ISL70002SEHEVAL1Z evaluation board is designed to
demonstrate the features of the ISL70002SEH, a TID and SEE
hardened 12A synchronous buck regulator IC with integrated
MOSFETs intended for Space applications. For more detailed
information about the ISL70002SEH, please refer to the
ISL70002SEH datasheet (FN8264).
A schematic and BOM of the ISL70002SEHEVAL1Z evaluation
board are shown in Figure 1 and Table 1, respectively. The
schematic indicates the test points, which allow many nodes
of the evaluation circuit to be monitored directly. The BOM
shows components that are representative of the types
needed for a design, but these components are not spacequalified. Equivalent space-qualified components would be
required for flight applications. A 1µH inductor is
recommended for 500kHz and a 500µH inductor is
recommended for 1MHz.
The ISL70002SEHEVAL1Z evaluation board accepts a nominal
3V to 5.5V input voltage and provides a regulated output
voltage ranging from 0.8V to 85% of the input voltage at
output currents ranging from 0A to 12A. The output can be
quickly set to a preset voltage of 1.0V, or adjusted to an
alternate voltage using the onboard potentiometer. A PGOOD
(Power Good) signal goes high and lights a red LED to indicate
that the output voltage is within a ±11% typical regulation
window. A toggle switch is provided to conveniently enable or
disable the output voltage.
The ISL70002SEHEVAL1Z evaluation board can be set to run
from the nominal 500kHz or 1MHz internal oscillator of the
ISL70002SEH or synchronized to a 500kHz to 1MHz ±20%
external clock. Two ISL70002SEHEVAL1Z evaluation boards
can be synchronized to each other in a Master/Slave
configuration, providing nearly twice the output current while
switching 180° out-of-phase with respect to each other. See
AN1751, “ISL70002SEH 2-Phase Buck Regulator User Guide.”
Recommended Test Equipment
• A 0V to 6V power supply with at least 20A current capability
• An electronic load capable of sinking current up to 12A
• Two digital multimeters (DMMs)
• A 500MHz dual-trace oscilloscope
Quick Start
1. Toggle S1 to the down (OFF) position.
2. Turn on the power supply. Set the output voltage to 3.3V
and set the output current limit to 20A. Turn off the power
supply.
3. Connect the positive lead of the power supply to J1 and the
negative lead of the power supply to J2.
4. Turn on the electronic load and set the output current to 6A.
5. Connect the positive lead of the electronic load to J39 and
connect the negative lead of the electronic load to J40.
6. Configure one DMM to monitor the input voltage from TP7
to TP11.
FIGURE 1. PHOTOGRAPH OF ISL70002SEHEVAL1Z
April 12, 2012
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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.
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All other trademarks mentioned are the property of their respective owners.
Application Note 1732
7. Configure another DMM to monitor the output voltage from
TP13 to TP11.
8. Connect Channel 1 of the oscilloscope to J6 (or from TP33 to
TP28) to monitor the rectangular waveform on the LXx pins.
9. Connect Channel 2 of the oscilloscope to J14 (or from TP36 to
TP37) to monitor the output voltage. Ripple voltage is
customarily measured with 20MHz bandwidth limiting
10. Toggle S1 to the up (ON) position.
11. Verify the output voltage is 1.0V ±3% and the frequency of the
LXx waveform is 1MHz ±10%.
Layout Guidelines
1. Use an eight layer PCB with 2 ounce (70µm) copper or
equivalent in thinner layers.
2. 2 layers should be dedicated for ground plane.
3. Top and bottom layers should be used primarily for signals,
but can also be used to increase the VIN, VOUT and ground
planes as required.
4. Connect all AGND, DGND and PGNDx pins directly to the
ground plane. Connect all PVINx pins directly to the VIN
portion of the power plane.
6. Locate the output voltage resistive divider as close as
possible to the FB pin of the IC. The top leg of the divider
should connect directly to the load and the bottom leg of the
resistive divider should connect directly to AGND. The junction
of the resistive divider should connect directly to the FB pin.
7. Use a small island of copper to connect the LXx pins of U1 to
the inductor(s), L1 and L2, to minimize the routing
capacitance that degrades efficiency. Separate the island
from ground and power planes as much as possible.
8. Keep all signal traces as short as possible.
9. A small series snubber (R25 and C20) connected from the
LXx pins to the PGNDx pins may be used to dampen ringing
on the LXx pins if desired.
10. For optimum thermal performance, place a pattern of vias on
the top layer of the PCB directly underneath U1. Connect the
vias to the ground planes which serves as a heatsink. Thermal
interface material such as a Sil-Pad should be used to fill the
gap between the vias and the bottom of U1 to insure good
thermal contact. Using a Sil-Pad has the added benefit of
raising the bottom of U1 from the PCB surface so that a slight
bend can be added to the leads for strain relief.
5. Locate ceramic bypass capacitors as close as possible to U1.
Prioritize the placement of the bypass capacitors on the pins
of U1 in the order shown: PVINx, REF, AVDD, DVDD, SS, EN,
PGOOD.
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ISL70002SEH
Application Note 1732
FIGURE 2. ISL70002SEHEVAL1Z BOARD SCHEMATIC
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TABLE 1. ISL70002SEHEVAL1Z BILL OF MATERIALS
PART NUMBER
REF DES
QTY
VALUE
TOL.
C0805C103K2RAC
C12, C14
2
0.01µF
10%
H1082-OPEN
C16
1
OPEN
C1812C472F2GAC
C17
1
H1045-00471-25V20
C1-C3
C0805C102K2RAC
4
JEDEC TYPE
MANUFACTURER
200V
805
CAP_0805
KEMET
Ceramic Chip Cap
10%
OPEN
1210
CAP_1210
GENERIC
Ceramic Chip Cap
4700pF
1%
200V
1812
CAP_1812
KEMET
Multilayer Cap
3
470pF
20%
25V
603
CAP_0603
GENERIC
Multilayer Cap
C20
1
1000pF
10%
200V
805
CAP_0805
KEMET
H1045-OPEN
C28, C29, C32,
C33, C35
5
OPEN
5%
OPEN
603
CAP_0603
GENERIC
C1825C224K2RAC
C31
1
0.22µF
10%
200V
1825
CAP_1825
KEMET
Ceramic Chip Cap
C1210C104K2RAC
C36
1
0.1µF
10%
200V
1210
CAP_1210
KEMET
Ceramic Chip Cap
T530D157M010AHE006
C4, C5, C11, C1,
C19, C21-C26
11
150µF
20%
10V
SMD
CAP_7343_31
KEMET
High Capacitance Ultra-Low ESR
Tantalum SMD Cap
C2225C105K2RAC
C6, C7, C10, C13,
C18, C27, C30, C34
8
1µF
10%
200V
2225
CAP_2225
KEMET
Multilayer Cap
C0805C682K2RAC
C8, C9
2
6800pF
10%
200V
805
CAP_0805
KEMET
Multilayer Cap
LTST-C170CKT
D1
1
SMD
LTST_C170CKT
LITEON
AlGaAs on GaAs Red LED
1N5822US
D2
0
SMD2
DIO_CASE_D-5B
MICROSEMI
3A 40V SCHOTTKY
BARRIER RECTIFIER
575-4
J1, J2, J39, J40
4
CONN
CON_BAN_575
KEYSTONE
SOLDER MOUNT
BANANA PLUG
JUMPER-3-100
J13, J18, J23,
J26-J29
7
THOLE
JUMPER-3
GENERIC
Three Pin Jumper
JUMPER2_100
J30-J32
3
THOLE
JUMPER-1
GENERIC
Two Pin Jumper
131-4353-00
J33, J36
2
CONN
TEK131-4353-00
TEKTRONIX
IHLP-2525CZ-ER-1R0-M-01
L1, L2
2
SMD
IND_IHLP-2525CZ-01
VISHAY
2N7002-7-F
Q1
1
SOT23
SOT23
FAIRCHILD
H2505-DNP-DNP-1
R12, R18
2
DNP
1%
DNP
603
RES_0603
GENERIC
Metal Film Chip Resistor
(Do Not Populate)
S0603CPZ1R00F10
R13, R14
2
1
1%
1/10W
603
RES_0603
State of the Art
100ppm Thick Film Chip
Resistor
S0603CA1002BEZ
R15
1
10k
0.10%
1/10W
603
RES_0603
State of the Art
25ppm Thin Film Chip Resistor
MCR03EZPFX1001
R16
1
1k
1%
1/10W
603
RES_0603
ROHM
20%
11A
DESCRIPTION
Ceramic Chip Cap
Multilayer Cap
Scope Probe Test
Point PCB Mount
LOW PROFILE HIGH CURRENT
INDUCTOR (RoHS COMPLIANT)
N-Channel EMF Effect
Transistor (Pb-Free)
Metal Film Chip Resistor
Application Note 1732
AN1732.0
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PACKAGE TYPE
1µH
VOLTAGE POWER
TABLE 1. ISL70002SEHEVAL1Z BILL OF MATERIALS (Continued)
PART NUMBER
REF DES
QTY
VALUE
TOL.
VOLTAGE POWER
5
JEDEC TYPE
MANUFACTURER
S0603CPZ1001F10
R17
1
1k
1%
H2511-00R00-1/16W1
R19
1
0
ERJ3GEY0R00V
R1-R7
7
S0603CA1501BEZ
R20
S0603CA1001BEZ
1/10W
603
RES_0603
State of the Art
100ppm Thick Film Chip
Resistor
1%
1/16W
603
RES_0603
GENERIC
Thick Film Chip Resistor
0
0%
1/10W
603
RES_0603
PANASONIC
Thick Film Chip Resistor
1
1.5k
0.10%
1/10W
603
RES_0603
State of the Art
25ppm Thin Film Chip Resistor
R21
1
1k
0.10%
1/10W
603
RES_0603
State of the Art
25ppm Thin Film Chip Resistor
S0603CPZ1000F10
R22
1
100
1%
1/10W
603
RES_0603
State of the Art
100ppm Thick Film
Chip Resistor
3299W-1-502-LF
R23
1
5k
10%
1/2W
RADIAL
RES_POT_3299W
BOURNS
TRIMMER POTENTIOMETER
(RoHS COMPLIANT)
H2511-01001-1/16W1
R24
1
1k
1%
1/16W
603
RES_0603
GENERIC
Thick Film Chip Resistor
H2513-001R8-1/8W1
R25
1
1.8
1%
1/8W
1206
RES_1206
GENERIC
Thick Film Chip Resistor
S0603CA1962BEZ
R8, R10
2
19.6k
0.10%
1/10W
603
RES_0603
State of the Art
25ppm Thin Film Chip Resistor
S0603CA4021BEZ
R9, R11
2
4.02k
0.10%
1/10W
603
RES_0603
State of the Art
25ppm Thin Film Chip Resistor
GT11MSCBE-T
S1
1
SMT
GT13MSCKE
C&K
1514-2
TP1, TP2, TP6,
TP10, TP12
5
THOLE
TP-150C100P
KEYSTONE
Test Point Turret 0.150
Pad 0.100 Thole
5002
TP3-TP5, TP7-TP9,
TP11, TP13
8
THOLE
MTP500X
KEYSTONE
Miniature White Test
Point 0.100 Pad 0.040 Thole
ISL70002SEHVF
U1
1
CQFP
CQFP64_555X555_635
INTERSIL
12A SYNCHRONOUS
BUCK REGULATOR W/MOSFET
Bergquist
Thermal Interface Material,
Sil-Pad, 12inx12inx0.020in, with
adhesive, cut to 0.4inx0.4in and
placed on underside of U1
SP2000-0.020-AC-1212
1
DESCRIPTION
SPDT On-None-On SMT
Ultraminiature Toggle Switch
(RoHS compliant)
Application Note 1732
PACKAGE TYPE
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Application Note 1732
FIGURE 3. TOP SIDE ASSEMBLY DRAWING
FIGURE 4. TOP LAYER
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Application Note 1732
FIGURE 5. LAYER 2
FIGURE 6. LAYER 3
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FIGURE 7. LAYER 4
FIGURE 8. LAYER 5
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FIGURE 9. LAYER 6
FIGURE 10. LAYER 7
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Application Note 1732
FIGURE 11. BOTTOM LAYER
FIGURE 12. BOTTOM SIDE ASSEMBLY DRAWING
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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