tb418

Using the EL7554 Demo Board
®
Technical Brief
November 14, 2003
TB418.1
Introduction
The EL7554 is a high efficiency fullfeatured synchronous 4A step-down
regulator. This document lists the
completed schematic diagram and BOM, as well as the
layout. With components on one side of the PCB, the
complete converter occupies less than 0.58in2 of space.
Please refer to the datasheet for the application of features.
This demo board is preset to 1.8V for VO and operates at
600kHz switching frequency. The measured crossover
frequencies are around 50kHz with the compensation
values.
Circuit Diagram
U1
R0
C0
0.018µF
2.32K
C1
OPEN
C2
0.018µF
R2
R1
10.2K
12.7K
VTJ
C4
0.018µF
L1
VOUT
TM
10.2K
R6
10.2K
R5
SEL
2.2µH
C5
47µF
GND
1 CC
SGND 28
2 VREF
COSC 27
C7
220pF
C11
OPEN
C12
OPEN
3 FB
STN 26
STN
4 VO
STP 25
STP
5 VTJ
EN 24
EN
6 TM
PG 23
7 SEL
PG
C8
VDD 22
0.22µF
8 LX
VIN 21
9 LX
VIN 20
10 LX
VIN 19
11 LX
PGND 18
12 LX
PGND 17
13 LX
PGND 16
14 NC
NC 15
C9
10µF
R4
OPEN
C10
10µF
VIN
GND
LX
EL7554IRE
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2003. All Rights Reserved. Elantec is a registered trademark of Elantec Semiconductor, Inc.
All other trademarks mentioned are the property of their respective owners.
Technical Brief 418
TABLE 1. DEMO BOARD BILL OF MATERIAL
DESIGNATOR
VALUE
PACKAGE
C0, C2, C4
0.018µF
0603
Any X5R or X7R
C5
47µF
1210
TDK
C7
220pF 5%
0603
Any 5% MLCC
C8
0.22µF
0603
Any X5R or X7R
C9, C10
10µF
1206
Any X5R or X7R
R0
2.32K/1%
0603
Any
R1
12.7K/1%
0603
Any
R2, R5, R6
10.2K/1%
0603
Any
L1
2.2µH
U1
EL7554IRE
HTSSOP-28
MANUFACTURER
PART NUMBER
C3225X5R0J476M
TDK
847-803-6100
RLF7030-2R2M5R4
Intersil
888-INTERSIL
EL7554IRE
The output voltage can be as high as the input voltage minus
the PMOS and inductor voltage drops. Use R1 and R2 to set
the output voltage according to the following formula:
R 1

V O = V FB ×  1 + ------
R

2
Where VFB=0.8V
When the resisters are changed, please change the
compensation capacitor C0 and resister R0. For the
convenience, standard values of R1 and R2 are listed in
Table 2.
R5 and R6 can be eliminated if voltage margin feature is not
used. Connect TM and SEL pins directly to ground.
2
PHONE #
The layout accommodates 1206, 1210, 1812, and D-size
package for C5.
TABLE 2. FEEDBACK RESISTER AND COMPENSATION
VALUES
VO (V)
C0 (pF)
R0 (kΩ)
R1 (kΩ)
R2 (kΩ)
0.8
0.018µF
1.02
0
Open
1
0.018µF
1.27
2.49
10
1.2
0.018µF
1.54
4.99
10
1.5
0.018µF
1.91
10
11.5
1.8
0.018µF
2.32
12.7
10.2
2.5
0.018µF
3.24
21.5
10
3.3
0.018µF
4.22
36
11.5
Technical Brief 418
Demo Board Layout
TOP SILKSCREEN
TOP LAYER
BOTTOM LAYER
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reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
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