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19-1436; Rev 1; 9/99
MAX1623 Evaluation Kit
_____________General
Description
The MAX1623 evaluation kit (EV kit) provides a preset
3.3V output voltage from a +4.5V to +5.5V input source.
It delivers up to 3A output current with greater than
90% efficiency.
The MAX1623 is a step-down switching regulator with
synchronous rectification that includes two low-on-
resistance 0.1Ω (max), 3A MOSFET power switches. It
features a resistor-programmable fixed off-time as well
as current-mode operation for superior load- and line-
transient response.
The MAX1623 EV kit can also be used to evaluate other
output voltages besides 3.3V by changing R
TOFF
and
the feedback resistors R1 and R2 located on the bot-
tom of the board.
____________________________Features
o
+4.5V to +5.5V Input Voltage Range
o
Output Voltage
3.3V Preset
1.1V to 3.8V Adjustable (optional
resistor-divider)
o
Guaranteed 3A Output Current
o
94% Efficiency (V
IN
= 5V, V
OUT
= 3.3V at I
OUT
= 2A)
o
Internal 3A, 0.1Ω (max) MOSFET Switches
o
Up to 350kHz Switching Frequency
o
Thermal Shutdown at T
j
= +145°C
o
Surface-Mount Construction
o
Fully Assembled and Tested
Evaluates: MAX1623
Component List
DESIGNATION QTY
C1
1
DESCRIPTION
220µF, 10V, low-ESR tantalum cap
Sprague 593D227X0010E2W or
AVX TPSE227M010R0100
330µF, 10V, low-ESR tantalum cap
Kemet T510X337M010AS
470pF ceramic capacitor
0.47µF ceramic capacitor
4.7µF, 16V tantalum capacitor
Sprague 595D475X0016A2B
Not installed
4.7µF, 10V X5R ceramic capacitor
Taiyo Yuden LMK316BJ475ML
4.7µH power inductor
Sumida CDRH125-4R4 or
Coiltronics UP2-4R7
110kΩ, 1% resistor
Not installed
10Ω, 5% resistor
MAX1623EAP (SSOP-20)
Shunts
3-pin headers
MAX1623 PC board
MAX1623 data sheet
SUPPLIER
AVX
Coiltronics
Dale-Vishay
Kemet
Motorola
Sprague
Sumida
Taiyo Yuden
PART
MAX1623EVKIT
Ordering Information
TEMP. RANGE
0°C to +70°C
IC PACKAGE
20 SSOP
C2
C3
C4
C5
C6, C7
C8
1
1
1
1
0
1
Component Suppliers
PHONE
803-946-0690
561-241-7876
402-564-3131
408-986-0424
602-303-5454
603-224-1961
708-956-0666
408-573-4150
FAX
803-626-3123
561-241-9339
402-563-6418
408-986-1442
602-994-6430
603-224-1430
708-956-0702
408-573-4159
L1
R
TOFF
R1, R2
R3
U1
None
JU1, JU2
None
None
1
1
0
1
1
2
2
1
1
Note:
Please indicate that you are using the MAX1623 when
contacting these component suppliers.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1623 Evaluation Kit
Evaluates: MAX1623
_________________________Quick Start
The MAX1623 EV kit is fully assembled and tested.
Follow these steps to verify board operation.
Do not
turn on the power supply until all connections are
completed.
1) Connect a 5V, 3A supply to the VIN pad. Connect
ground to the GND pad.
2) Connect a voltmeter and load, if any, to the VOUT
pad.
3) Verify that the shunt is across JU1 pins 2 and 3 for
normal operation.
4) Turn on the power supply to the board. Verify that
the output voltage is 3.3V.
5) To select other output voltages, refer to the
Setting
the Output Voltage
section in the MAX1623 data
sheet for instructions on selecting feedback resis-
tors R1 and R2.
Other Output Voltages
The MAX1623 EV kit is preset for a 3.3V output voltage.
However, the output voltage may also be adjusted by
an external voltage divider formed by R1 and R2 (locat-
ed on the bottom of the board). In addition, R
TOFF
must
be changed to obtain the desired switching frequency
(see
Switching Frequency and Programming the Off-
Time
in the MAX1623 data sheet). The only other modi-
fications required are to cut the trace across R1 and
remove the shunt from JU2. Refer to the
Setting the
Output Voltage
and
Output Filter Capacitor
sections in
the MAX1623 data sheet for instructions on selecting
feedback resistors R1 and R2 and output capacitor val-
ues.
PC Board Thermal Resistance
Junction to ambient thermal resistance greatly depends
on the amount of copper area immediately surrounding
the IC’s leads. This EV kit has 0.85 in.
2
of copper area
and has a measured thermal resistance of 45°C/W.
_______________Detailed Description
The MAX1623 EV kit provides a preset 3.3V output from
a +4.5V to +5.5V input voltage. It delivers up to 3A of
output current.
Table 1. Jumper JU1 Functions
(Shutdown Mode)
SHUNT
LOCATION
2&3
SHDN
PIN
MAX1623
OUTPUT
MAX1623 enabled,
V
OUT
= 3.3V
Shutdown mode,
V
OUT
= 0
Table 2. Jumper JU2 Functions
(FB Selection)
SHUNT LOCATION
1&2
Not installed
2&3
FBSEL PIN
Connected to VIN
Floating
Connected to GND
MAX1623
OUTPUT
V
OUT
= 2.5V
V
OUT
= 3.3V
Adjustable mode
Connected to VIN
1&2
Connected to GND
2
_______________________________________________________________________________________
MAX1623 Evaluation Kit
Evaluates: MAX1623
VIN
4.5V to 5.5V
C6
OPEN
C1
220µF
10V
R3
10Ω
C5
C8
4.7µF
10V
2
4
6
IN
IN
IN
V
CC
SHDN
V
IN
JU1 3
2
1
4.7µF
16V
R
TOFF
110k, 1%
14
7
SHDN
U1
MAX1623
LX
LX
LX
LX
LX
LX
1
3
5
20
18
16
L1
4.7µH
VOUT
3.3V
C7
OPEN
C2
330µF
10V
9
8
TOFF
FBSEL
REF
12
GND
11
15
PGND
17
PGND
19
PGND
FB
COMP
10
R2
OPEN
R1
SHORT
(PC TRACE)
VIN
1
JU2 2
3
C4
0.47µF
13
C3
470pF
V
OUT
= 1.10V 1 + R1
R2
(
)
NOTE:
HEAVY LINES DENOTE HIGH SWITCHING CURRENT PATHS.
TIE GND TO PGND AT A SINGLE LOCATION.
SHUNT
LOCATION
JU2 pins 1, 2
JU2 Not installed
(default)
JU2 pins 2, 3
FBSEL
PIN
Connected to VIN
Floating
MAX1623
OUTPUT
2.5V
3.3V
Adjustable output. Cut trace between
R1 pads. Refer to MAX1623 data
sheet for R1 and R2 values.
R
TOFF
(kΩ)
(for 300kHz)
180
110
Connected to GND
270
Figure 1. MAX1623 EV Kit Schematic
_______________________________________________________________________________________
3
MAX1623 Evaluation Kit
Evaluates: MAX1623
1.0"
1.0"
Figure 2. MAX1623 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX1623 EV Kit Component Placement Guide—
Solder Side
1.0"
1.0"
Figure 4. MAX1623 EV Kit PC Board Layout—Component Side
Figure 5. MAX1623 EV Kit PC Board Layout—Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
4
_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.

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