QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER 1 LT3430 DESCRIPTION Demonstration circuit 471 is a 60V, 200kHz, 2A load current, monolithic step-down DC/DC switching converter using the LT3430. With its wide input voltage range, 3A internal power switch, and thermally enhanced package, the LT3430 is a very versatile and powerful IC for DC/DC converters that require compact space and a wide variety of input voltage ranges. The constant 200kHz switching fre- quency allows all of the components to be small, surface mount devices. The current- mode control topology creates fast transient response and good loop stability with a mini- mum number of external compensation components and the use of ceramic input and output capacitors if desired. The low resis- tance internal power switch (0.1Ω) maintains high efficiencies >80% and up to 90%. The SHDN pin and 30µA shutdown current extend battery life. The wide input range allows step- down configurations with input voltages be- tween 5.5V and 60V. Both steady state and transient operation up to 60V is possible. Syn- chronization of switching frequencies up to 700kHz is possible. Demonstration Circuit 471 is a step-down converter using the LT3430. The circuit is de- signed for 7.5V60V input to 5.0V output at 2A load current for automotive, industrial, port- able computers, battery chargers, and dis- tributed power systems. This board was de- signed for wide input voltage range applica- tions where simplicity, small circuit size, and low component count are important as well as up to 2A of load current. The low-ESR tan- talum output capacitor reduces output volt- age ripple. Replacing this capacitor with a ceramic capacitor not only demonstrates small size and low cost, but the advantage of current-mode control in step-down applica- tions with a simple compensation network and a feedforward capacitor for more rug- ged stability and excellent transient response. Design files for this circuit board are available. Call the LTC factory. Table 1. Typical Performance Summary PARAMETER CONDITION VALUE Steady State Input Voltage Range V OUT = 5V, I OUT ≤ 2A 7.5 60V Maximum Transient Input Voltage All Vout (customized) 60V V OUT I OUT ≤ 2A 5V –3% Maximum Output Current 2A Typical Switching Frequency 200kHz Typical Efficiency V IN = 12V, V OUT = 5V, I OUT = 2A 86% Output Voltage Ripple V IN = 12V, V OUT = 5V, I OUT = 2A 30mV PP QUICK START PROCEDURE Demonstration circuit 471 is easy to set up to evaluate the performance of the LT3430. Re- fer to Figure 1 for proper measurement equip- ment setup and follow the procedure below: NOTE: Make sure that the input voltage does not exceed 60V. 1. Connect the 7.5V60V input power supply to the Vin and GND terminals on the board.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 · QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER 2 2. Connect an ammeter in series with the
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER
1
LT3430
DESCRIPTION Demonstration circuit 471 is a 60V, 200kHz, 2A load current, monolithic step-down DC/DC switching converter using the LT3430. With its wide input voltage range, 3A internal power switch, and thermally enhanced package, the LT3430 is a very versatile and powerful IC for DC/DC converters that require compact space and a wide variety of input voltage ranges. The constant 200kHz switching fre-quency allows all of the components to be small, surface mount devices. The current-mode control topology creates fast transient response and good loop stability with a mini-mum number of external compensation components and the use of ceramic input and output capacitors if desired. The low resis-tance internal power switch (0.1Ω) maintains high efficiencies >80% and up to 90%. The SHDN pin and 30µA shutdown current extend battery life. The wide input range allows step-down configurations with input voltages be-tween 5.5V and 60V. Both steady state and transient operation up to 60V is possible. Syn-
chronization of switching frequencies up to 700kHz is possible. Demonstration Circuit 471 is a step-down converter using the LT3430. The circuit is de-signed for 7.5V60V input to 5.0V output at 2A load current for automotive, industrial, port-able computers, battery chargers, and dis-tributed power systems. This board was de-signed for wide input voltage range applica-tions where simplicity, small circuit size, and low component count are important as well as up to 2A of load current. The low-ESR tan-talum output capacitor reduces output volt-age ripple. Replacing this capacitor with a ceramic capacitor not only demonstrates small size and low cost, but the advantage of current-mode control in step-down applica-tions with a simple compensation network and a feedforward capacitor for more rug-ged stability and excellent transient response. Design files for this circuit board are available. Call the LTC factory.
Table 1. Typical Performance Summary PARAMETER CONDITION VALUE Steady State Input Voltage Range VOUT = 5V, IOUT ≤ 2A 7.5 60V
Maximum Transient Input Voltage All Vout (customized) 60V
Demonstration circuit 471 is easy to set up to evaluate the performance of the LT3430. Re-fer to Figure 1 for proper measurement equip-ment setup and follow the procedure below:
NOTE: Make sure that the input voltage does not exceed 60V. 1. Connect the 7.5V60V input power supply
to the Vin and GND terminals on the board.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER
2
2. Connect an ammeter in series with the in-put supply to measure input current.
3. Connect either power resistors or an elec-tronic load to the Vout and GND terminals on the board.
4. Connect an ammeter in series with output load to measure output current.
5. Connect a voltmeter across the Vin and GND terminals to measure input voltage.
6. Connect a voltmeter across the Vout and GND terminal to measure output voltage.
7. After all connections are made, turn on in-put power and verify that the output volt-age is 5.0V.
8. The synchronization and shutdown func-tions are optional and their pins can be left floating (disconnected) if their functions are not being used.
+
–
+
–
+
–
+
–
+
–
+
–
+
–LOAD
OPTIONAL
Figure 1. Proper Measurement Equipment Setup
0
10
20
30
40
50
60
70
80
90
100
0 400 800 1.2k 1.6k 2.0k
LOAD CURRENT (mA)
EFFI
CIEN
CY (%
)
8VIN
12VIN
24VIN
48VIN
55VIN
Figure 2. Efficiency vs Load Current
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER
3
CUSTOMIZING THE BOARD The components assembled on the board are optimized for a wide input voltage range and a 5V output. The bandwidth can be in-creased for more specific input voltages such as 12V ±10% or 18V24V with 36V transient if desired (just a few examples). The adjustable feedback resistors allow the output voltage to be customized. For output voltages below 3V, the boost diode should be moved from D2 to D3 to provide the minimum boost voltage re-quired for the internal power switch. Make sure that the boost capacitor (C8) has a volt-age rating greater than or equal to the out-put voltage for applications where the boost diode is placed in D2. However, the boost capacitor must have a voltage rating greater
than the input voltage whenever the boost diode is placed in position D3. D4 is an optional boost voltage blocking di-ode. For custom applications in which the output voltage is significantly greater than 5V, this blocking diode reduces the boost driver voltage, reducing the power (and thus heat) dissipation inside the IC. It is recommended that a CMHZ5236B zener diode is used in D4 when VOUT = 12V and the junction tempera-ture is hot without the use of the zener. Note that in order to properly install D4, the small trace connecting the anode and cathode of D4 on the board must be separated (an Ex-acto knife works well) before D4 is soldered to the board.
D2
MMSD914
Vout
Ceramic
D1
30BQ060
C40.68uF
TDK 4.7uF Ceramic
C222nF
5V @2A
C3C5750X7R1H475K
C5
C4532X5R0J107M
R215.4k
U1LT3430EFE
Sw
Vin
Boos
t
Gnd
Bias
Vc
Fb
Sync
/Shdn
C1220pF
R13.3k
Vin8V to 40V
Sumida 22uH
IR
L1 CEI-122 220
Vout
R34.99k
TDK 100uF
Figure 3. FireWire peripheral application:
8V40V input, 5V output @2A with all ceramic capacitors and 3.0mm maximum component height.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER
10
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER
11
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
SHDN 5V@2A
VIN7.5V-60V
SYNC
1. ALL RESISTORS ARE IN OHMS, 0603. ALL CAPACITORS ARE IN MICROFARADS, 0603.
GND
NOTE: UNLESS OTHERWISE SPECIFIED
VOUT
GND
2. FOR ALL OPTIONAL COMPONENTS ON BOARDS: Q1, R5, R6, C9: SHOW OUTLINE AND REFERENCE DESIGNATORS. D3, D4: NO OUTLINE, SHOW REFERENCE DESIGNATORS. C6, C7, C8, R4: NO OUTLINE, NO REFERENCE DESIGNATORS. A
Wednesday, July 10, 2002 1 1
2A, 200KHz HIGH VOLTAGE BUCK CONVERTER
KIM T.
KEITH S.
A DC471A-1 * LT3430EFE
SCHEMATIC
SIZE
DATE:
DWG NO. REV
SHEET OF
TITLE:
CONTRACT NO.
APPROVALSDRAWN:
CHECKED:
APPROVED:
ENGINEER:
DESIGNER:
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035Phone: (408)432-1900
1630 McCarthy Blvd.
LTC Confidential-For Customer Use Only
VIN BOOST
SHDN
SYNC
SW
FB
VOUT
VC
E6
+C7OPT
R6OPT
R13.3k
C1220pF
R4OPT
R215.4k1%
L133uH
UP3B-3301 2
D1
SMC30BQ060
21
C20.022uF
E5
C8OPT
R34.99k1%
+C5100uF10V7343
C9OPT
E2
R5OPT
D3
OPT
MMSD914T12 1
D2
SOD123
MMSD914T121
U1LT3430EFE
3 4
15
14
713
1
8
9 16 11
12
10
5
2
6
VIN VIN
SHDN
SYNC
NCNC
GND
GNDGND GND VC
FB
BIAS
SW
SW
BOOST
Q1
OPTMMBT2222A
1
23
E3
D4
OPT
SMAZ7V52 1
C34.7uF100V
E4
C40.68uF16V
C6OPT0805
E1
Linear Technology CorporationLT3430EFE 2A, 200KHz HIGH VOLTAGE BUCK CONVERTERENG: KEITH S.
BILL OF MATERIALSDC471A-1
6/17/200512:07 PM
Item Qty Reference Part Description Manufacture / Part #