MAXIM MAX1945

19-2615; Rev 1; 1/03
MAX1945 Evaluation Kit
The MAX1945 evaluation kit (EV kit) is a fully assembled
and tested surface-mount circuit board that contains a
high-efficiency step-down switching-regulator circuit for
applications requiring on-board postregulation. The circuit utilizes a MAX1945R regulator featuring ±4% voltage
margining and is configured for a 1.8V output voltage.
The circuit provides up to 6A of current. A 2.6V to 5.5V
DC source can be utilized to power the circuit’s input.
The MAX1945R IC features an internal power MOSFET
switch and an internal synchronous rectifier. The
MAX1945 EV kit provides connections for the SYNC
input. It also provides an output to synchronize another
MAX1945 EV kit clock 180 degrees out-of-phase. Pulsewidth modulated (PWM) operation at 500kHz allows the
use of tiny surface-mount components.
Features
♦ 0.970in x 0.840in Circuit Footprint
♦ 2.6V to 5.5V Input Range
♦ Output Voltage
1.8V/2.5V Preset
0.8V to 0.85x VIN Adjustable
♦ Provides Up to 6A Output Current
♦ ±4% Voltage Margining
♦ Internal Power Switch and Synchronous Rectifier
♦ 500kHz/1MHz PWM Selectable Switching
Frequency
♦ SYNC Input: Synchronizes from 400kHz to 1.2MHz
TTL/CMOS Clock
♦ SYNC Output: Drives 2nd MAX1945 Switching 180
Degrees Out-of-Phase
Component List
DESIGNATION QTY
C1
C2
1
1
DESCRIPTION
180µF ±20%, 4V polymer capacitor
(7.3 x 4.3)
Panasonic EEFUE0G181R
0.1µF ±10%, 10V X7R ceramic
capacitors (0603)
AVX 0603ZC104KAT
1
0.22µF ±10%, 6.3V X7R ceramic
capacitor (0603)
AVX 06036C224KAT
C5
1
100pF ±5%, 50V COG ceramic
capacitor (0603)
TDK C1608COG1H101JT
C8
1
1µF ±10%, 16V X7R ceramic
capacitor (1206)
TDK C3216X7R1C105KT
C4
1
100mA, 30V Schottky diode (SOD-523)
Central Semiconductor CMOSH-3
J1
0
Scope probe connector (not installed)
FCI 33JR135-1
JU1, JU2, JU3
3
2-pin headers
D1
♦ Fully Assembled and Tested
100µF ±20%, 8V polymer capacitor
(7.3 x 4.3)
Panasonic EEFUE0K101R
3
C3, C6, C7
♦ All Surface-Mount Components
Ordering Information
PART
MAX1945EVKIT
TEMP RANGE
IC PACKAGE
0°C to +70°C
28 TSSOP-EP*
*EP = Exposed pad.
Quick Start
Required Equipment
The following equipment is required before beginning:
• One 2.6V to 5.5V power supply capable of providing 5A
• One voltmeter
The MAX1945 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:
1.8V Output Voltage (Nominal)
1) Verify that jumpers JU1 (CTL1) and JU2 (CTL2) do
not have shunts across their respective pins.
2) Verify that a shunt is across the pins of jumper JU3
(SYNC).
3) Verify that jumper JU4 (FBSEL, 1.8V) has a shunt
installed across pins 2 and 3.
4) Connect the voltmeter to the VOUT and PGND
pads.
________________________________________________________________ Maxim Integrated Products
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.
1
Evaluates: MAX1945
General Description
Evaluates: MAX1945
MAX1945 Evaluation Kit
Component List (continued)
DESIGNATION QTY
DESCRIPTION
JU4
1
3-pin header
L1
1
1.2µH, 9A inductor
Sumida CDRH8D43 4783-T010
R1
1
0Ω ±5% resistor (0603)
R2
0
Not installed, resistor (0603)
R3
1
180kΩ ±5% resistor (0603)
R4
1
10Ω ±5% resistor (0805)
R5, R6, R7
3
100kΩ ±5% resistors (0603)
U1
1
MAX1945REUI, 28-pin TSSOP-EP
None
4
Shunts (JU1–JU4)
None
1
MAX1945 PC board
5) Connect the 2.6VDC to 5.5VDC power supply to the
VIN pad. Connect the supply ground to the PGND
pad.
6) Turn on the power supply and verify that the output
voltage at VOUT is 1.8V.
For instructions on selecting the feedback resistors for
other output voltages, see the Evaluating Other Output
Voltages section.
Detailed Description
The MAX1945 EV kit contains a step-down switchingregulator circuit providing 1.8V and up to 6A at the
output. The circuit can be powered from a DC power
supply with an input range of 2.6V to 5.5V and supply
up to 5A of current.
The circuit utilizes a MAX1945R regulator IC with ±4%
voltage margining and is configured for a 1.8V output.
The output voltage is set to 1.8V by JU4 (FBSEL), external divider resistor R1, and the MAX1945R internal
resistor-dividers. The output can be reconfigured for
other output voltages. The voltage margining and shut-
down features are controlled by two multifeature
jumpers (JU1, JU2). The output voltage can be configured to operate at 1.8V (nominal), 1.87V (+4%), or
1.73V (-4%).
The MAX1945R IC in a TSSOP-EP package features an
internal power MOSFET switch and an internal synchronous rectifier. The EV kit’s four-layer PC board has copper pads under the IC and vias connecting to the
PGND layer (layer 2) to dissipate heat away from the
IC. This enables the EV kit to operate at high current
ratings.
The MAX1945 EV kit is configured to switch at 500kHz.
The EV kit can be reconfigured to switch at 1MHz or
use an external TTL/CMOS digital clock source. PC
board pads are provided for the MAX1945 IC’s SYNC
input and SYNCOUT signals. A second MAX1945 EV
kit’s SYNC input can be fed from the SYNCOUT signal.
This enables the second MAX1945 to switch 180
degrees out-of-phase relative to the first MAX1945R IC.
An oscilloscope jack (J1) can be installed on the EV kit
to obtain accurate voltage transient response and
output ripple measurement. Obtain the jack from the
manufacturer listed in the Component List for
Designation J1.
Jumper Selection
Shutdown Mode/Voltage Margining Control
The MAX1945 EV kit has two jumpers providing multifeature configurations. JU1 and JU2 configure the shutdown mode that reduces the MAX1945 quiescent
current and voltage-margining modes. The voltagemargining modes allow the output to be shifted to a
higher or lower supply tolerance. Table 1 lists the selectable jumper options for the shutdown and voltage-margining modes.
Synchronization and Frequency Selection
The MAX1945 EV kit provides a jumper to select the
switching frequency of the MAX1945R IC. Additionally,
the MAX1945R can be synchronized to an external
Component Suppliers
SUPPLIER
PHONE
FAX
WEBSITE
AVX
843-946-0238
843-626-3123
www.avxcorp.com
Central Semiconductor
631-435-1110
631-435-1824
www.centralsemi.com
Panasonic
714-373-7366
714-737-7323
www.panasonic.com
Sumida USA
847-545-6700
847-545-6720
www.sumida.com
TDK
847-803-6100
847-390-4405
www.component.tdk.com
Note: Please indicate that you are using the MAX1945 when contacting these component suppliers.
2
_______________________________________________________________________________________
MAX1945 Evaluation Kit
IC CTL1 PIN
JUMPER JU1
(SHUNT)
IC CTL2 PIN
JUMPER JU2
(SHUNT)
MAX1945 EV KIT
OUTPUT VOLTAGE
Connected to VCC
(none)
Connected to VCC
(none)
1.8V
(nominal output)
MAX1945 is enabled
Connected to GND
(installed)
Connected to VCC
(none)
1.87V
(+4% voltage margining)
MAX1945 is enabled
Connected to VCC
(none)
Connected to GND
(installed)
1.73V
(-4% voltage margining)
MAX1945 is enabled
Connected to GND
(installed)
Connected to GND
(installed)
0V
(output is OFF)
Table 2. Jumper JU3 Functions
MAX1945
FREQUENCY
SHUNT
LOCATION
SYNC PIN
None
Connected to VCC
1MHz switching
frequency
Installed
Connected to GND
500kHz switching
frequency
None; external
clock source
Connected to SYNC
PC board pad
External TTL/CMOS
digital clock provides
synchronization
TTL/CMOS digital clock. JU3 selects the switching
frequency or synchronization source for the
MAX1945R. Table 2 lists the jumper options.
Clock Selection (SYNC Input)
The MAX1945 EV kit’s circuit can be synchronized to an
external TTL/CMOS digital clock using the SYNC and
GND PC board pads. The external clock provides a
square wave with the following signal specifications:
• Output voltage:
Logic high = 1.6V (min) to 5V (max)
Logic low = 0V (min) to 0.4V (max)
• Output frequency: 400kHz to 1.2MHz
• Duty cycle: 10% to 90%
JU3 must be reconfigured for the external clock (see
Table 2).
MAX1945 STATUS
MAX1945 is in shutdown
mode
Dual Power-Supply Design (SYNCOUT)
The MAX1945 EV kit features a PC board pad for the
SYNCOUT signal connection to evaluate a dual
postregulated power-supply design. Utilizing the SYNCOUT signal as a TTL/CMOS digital clock to drive a
second MAX1945 EV kit enables the second
MAX1945R to switch 180 degrees out-of-phase relative
to the first EV kit. The second MAX1945 EV kit’s SYNC
input is driven by the SYNCOUT of the first EV kit. JU3
must be properly configured on both EV kits. The first
MAX1945 EV kit should be configured for 500kHz
switching frequency. The second EV kit must be configured for an external TTL/CMOS digital clock (see Table
2). Use the GND pad near the SYNC and SYNCOUT
pads on both EV kits for the clock GND.
Output Voltage Selection
The MAX1945 EV kit provides a jumper to select the
output voltage that the EV kit can provide. JU4 configures the EV kit for outputs of 1.8V, 2.5V, or an output
voltage determined by the R1 and R2 resistor-divider.
Table 3 lists the jumper options.
Evaluating Other Output Voltages
The MAX1945 EV kit step-down switching regulator
output is set to 1.8V by an internal feedback resistor
pair, resistor R1, and JU4. To generate output voltages
other than 1.8V (0.8V to 0.85x VIN), select different
external voltage-divider resistors R1 and R2. JU4 must
also be reconfigured. See Table 3 for configuring the
EV kit for other output voltages. Refer to the Setting the
Output Voltages section in the MAX1945 data sheet for
instructions on selecting feedback resistors R1 and R2,
and compensation components R3 and C5.
_______________________________________________________________________________________
3
Evaluates: MAX1945
Table 1. Jumpers JU1, JU2 Functions
Evaluates: MAX1945
MAX1945 Evaluation Kit
Table 3. Jumper JU4 Functions
SHUNT LOCATION
FBSEL PIN
FB PIN
MAX1945 EV KIT OUTPUT
1, 2
Connected to VCC
Connected to VOUT
2, 3
Connected to GND
Connected to VOUT
2.5V, resistor R1 = 0Ω
1.8V, resistor R1 = 0Ω
None*
Floating*
VOUT regulates when FB pin is 0.8V*
Output voltage set by resistors R1, R2*
*See the Evaluating Other Output Voltages section.
3
5
7
9
C3
0.1µF
LX
LX
LX
LX
LX
LX
LX
LX
1 BST
FB
D1
PGND
2 V
DD
PGND
4 IN
VCC
PGND
6 IN
PGND
8 IN
R4
10Ω
VIN
FBSEL
10 IN
PGND
C1
100µF
8V
26
1.2µH
22
15
25
R2
OPEN
23
21
19
16
VCC
1
2
JU4
VCC
R5
100kΩ
VCC
27
JU1
11
C6
0.1µF
12
13
R3
180kΩ
14
VCC
R6
100kΩ
VCC
28
CTL2
JU2
GND
R7
100kΩ
SYNC
17
REF
SYNC
SYNCOUT
18
SYNCOUT
JU3
COMP
C5
100pF
Figure 1. MAX1945 EV Kit Schematic
4
PGND
CTL1
VCC
C4
0.22µF
1
J1
OPEN
R1
0Ω
20
3
MAX1945
C2
180µF
4V
2
24
U1
C7
C8
1µF 0.1µF
VOUT
L1
_______________________________________________________________________________________
GND
MAX1945 Evaluation Kit
Figure 3. MAX1945 EV Kit Component Placement Guide—
Component Side
Figure 4. MAX1945 EV Kit PC Board Layout—Component Side
Figure 5. MAX1945 EV Kit PC Board Layout—Inner Layer,
Ground Plane
_______________________________________________________________________________________
Evaluates: MAX1945
Figure 2. MAX1945 EV Kit Component Placement Guide—
Solder Side
5
Evaluates: MAX1945
MAX1945 Evaluation Kit
Figure 6. MAX1945 EV Kit PC Board Layout—Inner Layer,
Power Plane
Figure 7. MAX1945 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.
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© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.