19-2080; Rev 0; 07/01
MAX1844 Evaluation Kit
General Description
The MAX1844 evaluation kit (EV kit) demonstrates the
MAX1844’s standard 4A application circuit. This DC-DC
converter steps down high-voltage batteries and/or AC
adapters, generating a precision, low-voltage rail for
use as chipset, DRAM, and other low-voltage supplies.
The MAX1844 EV kit provides a 1.8V output voltage
from a 7V to 24V battery input range. It delivers up to
4A output current with greater than 90% efficiency. The
EV kit operates at 300kHz switching frequency and has
superior line- and load-transient response.
This EV kit is a fully assembled and tested circuit
board. It also allows the evaluation of other output volt-
ages in the 1.0V to 5.5V range by changing feedback
resistors R1 and R2.
o
7V to 24V Input Voltage Range
o
Accurate Current Sense
o
Preset 1.8V/2.5V Output Voltage
o
1.0V to 5.5V Adjustable Output
o
4A Output Current
o
300kHz Switching Frequency
o
Power-Good Output
o
Over/Undervoltage Protection
o
20-Pin QSOP Package
o
Low-Profile Components
o
Fully Assembled and Tested
Features
Evaluates: MAX1844
Ordering Information
PART
MAX1844EVKIT
TEMP. RANGE
0
o
C to +70
o
C
IC PACKAGE
20 QSOP
Component List
DESIGNATION QTY
C1
1
DESCRIPTION
10µF, 25V ceramic capacitor (1812)
Taiyo Yuden TMK432BJ106KM or
TDK C4532X5R1E106M
330µF, 6.3V 40mΩ low-ESR
capacitor
Sanyo 6TPB330M
0.1µF ceramic capacitor (0805)
0.22µF ceramic capacitor (1206)
4.7µF, 10V X5R ceramic capacitor
(1206)
Taiyo Yuden LMK316BJ475ML
3.3µF, 10V X5R ceramic capacitor
(1206)
Taiyo Yuden LMK316BJ335ML
2200pF ceramic capacitor (0805)
1A Schottky diode
Nihon EP10QY03,
International Rectifier 10MQ040N,
or Nihon EC10QS03
100mA, 30V Schottky diode
Central Semiconductor CMPSH-3
U1
JU1, JU2
JU9, JU10
None
None
None
None
1
2
2
4
1
1
1
DESIGNATION QTY
L1
N1A, N1B
C2
C3
C4
C5
1
1
1
1
R1, R2, R11,
R13, R14, R15
R3
R4
R5, R6
R7
R8
R9
R10
1
1
0
1
1
2
1
1
1
1
DESCRIPTION
4.7µH power inductor
Sumida CDRH124-4R7MC
Dual N-channel MOSFET
Fairchild FDS6982A
Not installed (0805)
130kΩ
±1%
resistor (0805)
100kΩ
±5%
resistor (0805)
1MΩ
±5%
resistors (0805)
20Ω
±5%
resistor (0805)
200Ω
±5%
resistor (0805)
274kΩ
±1%
resistor (0805)
0.015Ω
±1%
1/2W resistor (2010)
IRC LR2010-01-R015-F or
Dale WSL-2010-R015F
MAX1844EEP (20-pin QSOP)
2-pin headers
3-pin headers
Shunts (JU1, JU2, JU9, JU10)
MAX1844 PC board
MAX1844 data sheet
MAX1844 EV kit data sheet
C6
C7
1
1
D1
1
D2
1
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX1844 Evaluation Kit
Evaluates: MAX1844
Component Suppliers
SUPPLIER
Central Semiconductor
Dale
Fairchild
IR
IRC
Nihon
Sanyo
Sumida
Taiyo Yuden
TDK
PHONE
516-435-1110
402-564-3131
408-721-2181
310-322-3331
361-992-7900
847-843-7500
619-661-6835
708-956-0666
408-573-4150
847-390-4373
FAX
516-435-1824
402-563-6296
408-721-1635
310-252-7175
361-992-3377
847-843-2798
619-661-1055
708-956-0702
408-573-4159
847-390-4428
The output voltage can also be adjusted between 1.0V
and 5.5V by selecting R1 and R2 values. Cut the PC
board trace shorting JU7, then select feedback resistor
R2 in the 5kΩ to 50kΩ range. R1 is then given by:
R1 = R2 ((V
OUT
/ V
FB
) - 1)
where V
FB
= 1.0V. See MAX1844 data sheet for opti-
mizing components for output voltage selection.
Jumper Settings
Table 1. Jumper JU1 Functions
(Shutdown Mode)
SHUNT
LOCATION
ON
OFF
SHDN/PIN
Connected to VCC
Connected to GND
MAX1844
OUTPUT
MAX1844 enabled
Shutdown mode,
V
OUT
= 0
Note:
Please indicate that you are using the MAX1844 when
contacting these component suppliers.
Equipment Needed
• 7V to 24V power supply, battery, or notebook AC
adapter
• DC bias power supply, 5V at 100mA
• Dummy load capable of sinking 4A
• Digital multimeter (DMM)
• 100MHz dual-trace oscilloscope
ON
Connected to VCC
Table 2. Jumper JU2 Functions
(Low-Noise Mode)
SHUNT
LOCATION
SKIP/PIN
OPERATIONAL
MODE
Low-noise mode,
forced fixed-frequency
PWM operation.
Normal operation,
allows automatic
PWM/PFM switchover
for pulse skipping at
light load, resulting in
highest efficiency.
Quick Start
1) Ensure that the circuit is connected correctly to the
supplies and dummy load prior to applying any
power.
2) Verify that the shunts are across JU1, JU2, JU9 pins
1 and 2, and JU10 pins 2 and 3.
3) Turn on battery power prior to +5V bias power; oth-
erwise, the output UVLO timer will time out and the
FAULT latch will be set, disabling the regulator until
+5V power is cycled or shutdown is toggled.
4) Observe the 1.8V output with the DMM and/or oscil-
loscope. Look at the LX switching-node and MOS-
FET gate-drive signals while varying the load current.
OFF
Connected to GND
Table 3. Jumper JU3 Functions
(Fixed/Adjustable Current-Limit Selection)
SHUNT
LOCATION
ON
ILIM PIN
Connected to VCC,
(remove R3/R9 divider)
Connected to REF
through voltage-divider
R3/R9. Refer to the
Current-Limit Circuit
section in the MAX1844
data sheet for
information on selecting
R3/R9.
CURRENT-LIMIT
THRESHOLD
100mV
Detailed Description
Evaluating Other Output Voltages
The EV kit output is preset to +1.8V. If a 2.5V output is
desired, cut the trace shorting JU7 and install a short
across R2.
OFF
Adjustable from
25mV to 200mV.
Programmed for
65mV by R3 and
R9.
2
_______________________________________________________________________________________
MAX1844 Evaluation Kit
Evaluates: MAX1844
Table 4. Jumpers JU4, JU5, and JU6 Functions (Switching-Frequency Selection)
JU4
Not Installed
Installed
Not Installed
Not Installed
JU5
Not Installed
Not Installed
Installed
Not Installed
JU6
Not Installed
Not Installed
Not Installed
Installed
TON PIN
Floating
Connected to VCC
Connected to REF
Connected to GND
FREQUENCY (kHz)
300 (as shipped)
200
450
600
Important:
Don’t change the operating frequency without first recalculating component values. Frequency has a significant effect on
preferred inductor value, peak current-limit level, MOSFET heating, PFM/PWM switchover point, output noise, efficiency, and other critical
parameters.
Table 5. Jumper JU7 Functions
(Output Voltage Selection)
JU7
Installed
Not
Installed
Installed
FB PIN
Connected to VCC
Connected to GND
through R2
(R1 = open)
Short on R2
OUTPUT VOLTAGE
V
OUT
= 1.8V (default)
V
OUT
= 2.5V
Table 7. Jumper JU9 Functions
(Undervoltage Protection Selection)
JU9
1 and 2
2 and 3
UVP PIN
Connected to VCC
Connected to GND
Connected to
resistor-divider
R14/R15
UVP THRESHOLD
UVP is enabled.
UVP threshold is 70%
of nominal.
UVP is disabled.
Refer to the MAX1844
data sheet for
information on setting
UVP in adjustable
mode.
Adjustable from 1V to
5.5V
Refer to the MAX1844
data sheet for
information on setting
V
OUT
in adjustable
mode.
Not Installed
Not
Installed
Connected to
resistor-divider
R1/R2
Table 6. Jumper JU8 Functions
(Latching/Nonlatching Overvoltage
Protection)
JU8
1 and 2
2 and 3
LATCH PIN
Connected to VCC
Connected to GND
OVP BEHAVIOR
Nonlatching
Latching (default)
Table 8. Jumper JU10 Functions
(Overvoltage Protection Selection)
JU10
1 and 2
2 and 3
OVP PIN
Connected to VCC
Connected to
GND
OVP THRESHOLD
OVP is disabled.
OVP is enabled. OVP
threshold is 114.5%
of nominal.
Refer to the MAX1844
data sheet for
information on setting
OVP in adjustable
mode.
Not Installed
Connected to
resistor-divider
R13/R11
_______________________________________________________________________________________
3
MAX1844 Evaluation Kit
Evaluates: MAX1844
VBIAS
+5V
C5
4.7µF
10V
VCC
R7
20Ω
C6
3.3µF
10V
D2
CMPSH-3
VBATT
7V TO 24V
13
16
VCC
V+ V
DD
14
V
CC
BST
18
20
19
C3
0.1µF
7
4
5
6
N1-B
C1
10µF
25V
L1
4.7µH
D1
VOUT
1.8V
SHDN
JU1
R5
1MΩ
3
VCC
DH
SHDN
LX
U1
ILIM
DL
MAX1844
3
REF
R9
274kΩ
1%
JU3
7
R3
130kΩ
1%
VCC
JU2
17
R6
1MΩ
8
JU5
450KHz
C4
0.22µF
FLOAT = 300kHz 15
JU6
600KHz
2
LATCH
VCC
SKIP
8
N1-A
12
1
2
C2
330µF
6.3V
R1
OPEN
1
SKIP
CS
REF
2V
OUT
REF
6
C7
2200pF
5
R10
0.015Ω
1%
R8
200Ω
GND
VCC
JU7
VCC
R4
100kΩ
PGOOD
R2
OPEN
VCC
JU4
VCC 200KHz
1
2
3
JU8
FB
TON
PGOOD
10
VCC
9
UVP
4
R13
OPEN
REF
JU10 1
2
3
R11
OPEN
R15
OPEN
1
2
JU9
3
OVP
R14
OPEN
REF
GND
11
Figure 1. MAX1844 EV Kit Schematic
4
_______________________________________________________________________________________
MAX1844 Evaluation Kit
Evaluates: MAX1844
1.0"
1.0"
Figure 2. MAX1844 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX1844 EV Kit PC Board Layout—Component Side
1.0"
Figure 4. MAX1844 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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ______________________5
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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