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19-2615; Rev 1; 1/03
MAX1945 Evaluation Kit
General Description
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. 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
Features
Evaluates: MAX1945
Component List
DESIGNATION QTY C1 1 DESCRIPTION 100F 20%, 8V polymer capacitor (7.3 x 4.3) Panasonic EEFUE0K101R 180F 20%, 4V polymer capacitor (7.3 x 4.3) Panasonic EEFUE0G181R 0.1F 10%, 10V X7R ceramic capacitors (0603) AVX 0603ZC104KAT 0.22F 10%, 6.3V X7R ceramic capacitor (0603) AVX 06036C224KAT 100pF 5%, 50V COG ceramic capacitor (0603) TDK C1608COG1H101JT 1F 10%, 16V X7R ceramic capacitor (1206) TDK C3216X7R1C105KT 100mA, 30V Schottky diode (SOD-523) Central Semiconductor CMOSH-3 Scope probe connector (not installed) FCI 33JR135-1 2-pin headers
All Surface-Mount Components Fully Assembled and Tested
Ordering Information
PART MAX1945EVKIT TEMP RANGE 0C to +70C IC PACKAGE 28 TSSOP-EP*
C2
1
*EP = Exposed pad.
C3, C6, C7
3
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:
C4
1
C5
1
C8
1
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.
D1 J1 JU1, JU2, JU3
1 0 3
________________________________________________________________ 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.
MAX1945 Evaluation Kit Evaluates: MAX1945
Component List (continued)
DESIGNATION QTY JU4 L1 R1 R2 R3 R4 R5, R6, R7 U1 None None 1 1 1 0 1 1 3 1 4 1 DESCRIPTION 3-pin header 1.2H, 9A inductor Sumida CDRH8D43 4783-T010 0 5% resistor (0603) Not installed, resistor (0603) 180k 5% resistor (0603) 10 5% resistor (0805) 100k 5% resistors (0603) MAX1945REUI, 28-pin TSSOP-EP Shunts (JU1-JU4) MAX1945 PC board
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.
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.
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
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-
Component Suppliers
SUPPLIER AVX Central Semiconductor Panasonic Sumida USA TDK PHONE 843-946-0238 631-435-1110 714-373-7366 847-545-6700 847-803-6100 FAX 843-626-3123 631-435-1824 714-737-7323 847-545-6720 847-390-4405 WEBSITE www.avxcorp.com www.centralsemi.com www.panasonic.com www.sumida.com www.component.tdk.com
Note: Please indicate that you are using the MAX1945 when contacting these component suppliers. 2 _______________________________________________________________________________________
MAX1945 Evaluation Kit
Table 1. Jumpers JU1, JU2 Functions
IC CTL1 PIN JUMPER JU1 (SHUNT) Connected to VCC (none) Connected to GND (installed) Connected to VCC (none) Connected to GND (installed) IC CTL2 PIN JUMPER JU2 (SHUNT) Connected to VCC (none) Connected to VCC (none) Connected to GND (installed) Connected to GND (installed) MAX1945 EV KIT OUTPUT VOLTAGE 1.8V (nominal output) 1.87V (+4% voltage margining) 1.73V (-4% voltage margining) 0V (output is OFF) MAX1945 STATUS
Evaluates: MAX1945
MAX1945 is enabled MAX1945 is enabled MAX1945 is enabled MAX1945 is in shutdown mode
Table 2. Jumper JU3 Functions
SHUNT LOCATION None Installed None; external clock source SYNC PIN Connected to VCC Connected to GND Connected to SYNC PC board pad MAX1945 FREQUENCY 1MHz switching frequency 500kHz switching frequency External TTL/CMOS digital clock provides synchronization
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.
TTL/CMOS digital clock. JU3 selects the switching frequency or synchronization source for the MAX1945R. Table 2 lists the jumper options.
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.
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).
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.
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MAX1945 Evaluation Kit Evaluates: MAX1945
Table 3. Jumper JU4 Functions
SHUNT LOCATION 1, 2 2, 3 None* FBSEL PIN Connected to VCC Connected to GND Floating* FB PIN Connected to VOUT Connected to VOUT VOUT regulates when FB pin is 0.8V* MAX1945 EV KIT OUTPUT 2.5V, resistor R1 = 0 1.8V, resistor R1 = 0 Output voltage set by resistors R1, R2*
*See the Evaluating Other Output Voltages section.
3 5 7 9 C3 0.1F D1
LX LX LX LX
LX LX LX LX FB PGND PGND PGND PGND FBSEL
26 24 22 20 15 25 23 21 19 16
L1 1.2H C2 180F 4V 2
VOUT
1 J1 OPEN PGND
R1 0
1 BST
2V DD 4 IN VCC 6 IN R4 10 VIN C1 100F 8V C7 C8 1F 0.1F 8 IN 10 IN
R2 OPEN
VCC 1 2 3 JU4 VCC R5 100k VCC JU1 R6 100k VCC JU2 R7 100k SYNC SYNCOUT
U1
PGND
MAX1945
CTL1
27
VCC C6 0.1F
11 12
VCC GND
28 CTL2
13 R3 180k C4 0.22F C5 100pF
17 REF SYNC SYNCOUT COMP 18 JU3
14
GND
Figure 1. MAX1945 EV Kit Schematic
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MAX1945 Evaluation Kit Evaluates: MAX1945
Figure 2. MAX1945 EV Kit Component Placement Guide-- Solder Side
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
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MAX1945 Evaluation Kit Evaluates: MAX1945
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.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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