Microsemi LX1918 User manual

LX1918 EVALUATION BOARD USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
Page 1
Copyright ©2004
Rev. 1.2, 2005-12-02
SYNCHRONOUS BUCK CONVERTER
LX1918 EVALUATION BOARD
INTEGRATED PRODUCTS

LX1918 EVALUATION BOARD USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
Page 2
Copyright ©2004
Rev. 1.2, 2005-12-02
TABLE OF CONTENTS
LX1918 EVAL Introduction................................................................................................................................3
Schematic for LX1918 Evaluation Board............................................................................................................... 4
Hook Up................................................................................................................................................................. 5
Connections........................................................................................................................................................... 6
Bill of Materials....................................................................................................................................................... 6

LX1918 EVALUATION BOARD USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
Page 3
Copyright ©2004
Rev. 1.2, 2005-12-02
INTRODUCING TO PRODUCT
The LX1918 Evaluation Board is available from Microsemi for demonstrating the performance of the LX1918
Synchronous Buck Converter.
KEY FEATURES
•2.7V to 6.0V Input Range
•1.5A Output Current
•1Mhz free running or 500KHz to 1.25MHz Switching Frequency
•0.6V Reference Voltage Adjustment
•PFM or PWM Mode
•EMI Support With Force PWM Mode
•Light Load Support: IOUT < 300mA
•> 95% Efficiency
•Quiescent Current Typical 400µA
•No External Schottky Diode
•Thermal Shutdown
•Cycle By Cycle Switch Current Limit
•UVLO Protection
•Current Limiting in Hiccup Mode
•8-Pin MLP package (3mm2)
APPLICATIONS
•Lower Power Embedded Applications
•WLAN Power Systems
•Portable Design with Single Cell LiIon or 3 Cell NiMH / NiCd
•Low Power Portable Storage Application
PART SPECIFIC INFORMATION
Part Number Description
LX1918CLD 1.5A Step-Down Synchronous Converter
TABLE 1–PART INFORMATION
IC EVALUATION BOARDS
LX1918CLD LX1918-LD EVAL
TABLE 2–EVALUATION BOARD INFORMATION

LX1918 EVALUATION BOARD USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
Page 4
Copyright ©2004
Rev. 1.2, 2005-12-02
SCHEMATIC FOR LX1918 EVAL
R3
10K PVIN
R5 40
C3
0.1µF
GND
C1
4.7µF
VIN
PVIN
L1 3.3µH VOUT
R1
1.5K
R2 1K
C2
47µF
GND
R4
10K PVIN
PVIN
AVIN
MODE
FB ES
AGND
PGND
SW
U1 LX1918
1
2
3
45
6
7
8
LO EMI
HI EFF
ENOSC
SHDN
P1
MODE
P2
E/S
Figure 1 – Evaluation Board Schematic

LX1918 EVALUATION BOARD USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
Page 5
Copyright ©2004
Rev. 1.2, 2005-12-02
LX1918 EVALUATION HOOK UP
The following is a demonstration scenario to be used
for evaluating the LX1918.
HOOK UP DIRECTION
1. Place Mode Jumper in HI EFF (high
efficiency) position.
2. Place E/S Jumper in ENOSC position.
3. Apply 3.6V / 2A input between VIN and
GND.
4. Connect to Load capable of handling the
prescribed output (Board is set to 1.5V
output by default).
R2 R1
INTEGRATED PRODUCTS
EVALUATION PCB
LX1918 STEP-DOWN SYNCHRONOUS CONVERTER
L1
31
ENOSC SHDN
LO EMI
E/S
HI EFF
VIN
GND
31
MODE
VOUT
C1
R3
R4
VIN
Vout
U
1
R5
C3
C2
GND
+
_
Power
IN
+
_
External
SYNC
500Khz-1.25Mhz Min
1.6V signal
Note: to use external sync
mode select must be in
LO EMI mode
Load
+
-
Figure 2 – Evaluation Board Hook Up
.

LX1918 EVALUATION BOARD USER GUIDE
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
Page 6
Copyright ©2004
Rev. 1.2, 2005-12-02
CONNECTIONS
The LX1918 Evaluation board has 4 test lead
attachment points for applying power and control
signals and for monitoring voltages. There are also 2
– 3 pin connections to select external synchronization
and operating mode. The E/S selector also has
shutdown capability
Function Board Label Connection
Input Power VIN Power Supply (2.70V ±6.0V)
Power Ground GND Common Power Supply Ground
External Sync / Shutdown E/S Connect to GND to disable LX1918. A PWM > 500KHz logic
PWM signal can also be applied1.
Output Voltage VOUT Test Point – Hook up load and monitor VOUT
Mode Select Mode High Efficiency = Pin 2 and 3. Low EMI = Pin 1 and 2.
1 – To use external synchroization feature the Mode Select must be in Lo EMI position.
BILL OF MATERIALS
MISCELLANEOUS COMPONENTS
Line
Item Part Description Manufacturer & Part # Case Reference Designators Qty
1 1.5A Synchronous Buck Converter MICROSEMI LX1918CLD LD U1 1
2 Inductor 1.8A Shielded SMD 3.3µH COILCRAFT MOS6020-332MX L1 1
3 Header 3 Pin .100 P1, P2 2
4 Test Point – 0.045 diameter, Wire Loop KEYSTONE 5004_Term 4
5 PCB SGE # 3534 X1
CAPACITORS
Line
Item Part Description Part Description Case Reference
Designators Qty
1 Capacitor, 4.7µF, X5R, 10V, 20% TAIYO YUDEN CELDK212BJ475MG 0805 C1 1
2 Capacitor, 47µF, X5R, 6.3V, 20% TAIYO YUDEN JMK325BJ476MM 1210 C2 1
3 Capacitor, 0.1µF, X5R, 16V, 20% TAIYO YUDEN CEEMK107BJ104MA 0603 C3 1
RESISTORS
Line
Item Part Description Part Description Case Reference
Designators Qty
1 Resistor, 1.5K, 1/16W, 5% PANASONIC ERJ-3GSYJ152V 0603 R1 1
2 Resistor, 1K, 1/16W, 5% PANASONIC ERJ-3GSYJ102V 0603 R2 1
3 Resistor, 10K, 1/16W, 5% PANASONIC ERJ-3GSYJ103V 0603 R3, R4 2
4 Resistor, 40.2, 1/10W, 1% PANASONIC ERJ-3EKF40R2 0603 R5 1