QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE LT3433 DESCRIPTION Demonstration circuit 527 is a monolithic step-up / stepdown DC/DC switching converter with Burst Mode™ featuring the LT3433. The board is optimized for 5V output at up to 400mA load current (12VIN) and an input voltage range of 4V to 60V. With its wide input voltage range, 500mA internal power switches, 100µA quiescent current during Burst Mode, 200kHz switching frequency and thermally enhanced package, the LT3433 is a very versatile and powerful IC for DC/DC converters that require both step-up and step-down capability for 5VOUT as well as compact space, high efficiency, low cost, and tolerance to high input voltage transients. The LT3433 200kHz switching frequency 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 minimum number of external components. The SHDN pin can be used to program undervoltage lockout or place the part in micropower shutdown, reducing supply current to 10µA (25µA maximum) by driving the pin low. Burst Mode operation is jumper selectable for extremely low, light load quiescent current. The LT3433 datasheet gives a complete description of the part, operation and applications information. The datasheet must be read in conjunction with this Quick Start Guide for demonstration circuit 527. The LT3433 is assembled in a small 16-pin thermally enhanced package with exposed pad. Proper board layout is essential for maximum thermal performance. Design files for this circuit board are available. Call the LTC factory. Burst Mode is a trademark of Linear Technology Corporation. Table 1. Typical Performance Summary (TA = 25°C) PARAMETER CONDITION Input Voltage Range Zero Load Input Current VOUT Maximum Output Current Output Voltage Ripple Light Load Output Voltage Ripple Switching Frequency Efficiency VALUE 4–60V Burst Mode ON, IOUT = 0A, VIN = 12V 120µA Burst Mode OFF, IOUT = 0A, VIN = 12V 1.0mA VIN = 4V to 60V, ISW(PK) ≤ 500mA 5V ± 3% VIN = 4V, VOUT = 5V 125mA VIN = 12V, VOUT = 5V 400mA VIN = 48V, VOUT = 5V 340mA VIN = 4V, VOUT = 5V, IOUT = 125mA 75mVPK–PK VIN = 12V, VOUT = 5V, IOUT = 400mA 25mVPK–PK VIN = 48V, VOUT = 5V, IOUT = 340mA 35mVPK–PK VIN = 12V, VOUT = 5V, IOUT = 5mA, Burst Mode ON 18mVPK–PK VIN = 12V, VOUT = 5V, IOUT = 5mA, Burst Mode OFF 7mVPK–PK VIN = 4V to 60V, VOUT = 5V 200kHz VIN = 4V, IOUT = 100mA, VOUT = 5V 58% VIN = 12V, IOUT = 400mA, VOUT = 5V 80% VIN = 48V, IOUT = 300mA, VOUT = 5V 71% 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE QUICK START PROCEDURE Demonstration circuit 527 is easy to set up to evaluate the performance of the LT3433. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: NOTE: Make sure that the input voltage does not exceed 60V. NOTE: The shutdown function is optional and its pin can be left floating (disconnected) if not being used. NOTE: Do not hot-plug the input voltage terminal VIN. The absolute maximum voltage on VIN is 60V and hotplugging a power supply through wire leads to the demonstration card can cause the voltage on the extremely low-ESR ceramic input capacitor to ring to twice its DC value. This is due to high currents instantaneously generated in the inductive supply leads from an input voltage step on the low-ESR ceramic input capacitor. A bulky higher-ESR capacitor, and an additional inductive filter can be added to the circuit to dampen hot-plug transient ringing. See Application Note 88 for more details. A transient voltage suppressor diode may also be used to absorb transient overvoltage. 1. Connect the power supply (with power off), load, and meters as shown in Figure 1. 2. After all connections are made, turn on input power and verify that the output voltage is 5V. NOTE: If the output voltage is too low, temporarily disconnect the load to make sure that the load is not set too high. 3. Once the proper output voltages are established, ad- just the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. Figure 1. Proper Measurement Equipment Setup CUSTOM OPTIONS OUTPUT VOLTAGE The components assembled on the board are optimized for a wide input voltage range and a 5V output. The feedback resistors (R2, R3) can be changed to adjust the output voltage according to the following equation: VOUT = 1.23 (1 + R2/R3) COMPENSATION Demonstration Circuit 527 has a frequency compensation network that is optimized for the tantalum output capacitor C5, the wide input voltage range 4V to 60V, and 5V output. Improved loop bandwidth can be achieved for various output voltages, output capacitors, and input voltage ranges by adjusting R1, C4, and C3. For more information, see the ‘Frequency Compensation’ section in the Application Note 19 or Application Note 76. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE SOFT START The soft start capacitor C6 controls the peak switch current during startup by holding down the output of the error amplifier as it charges up. The soft start capacitor forces the peak switch current to start at zero. Output voltage overshoot can be reduced or eliminated using this capacitor. The time that it takes for the converter to reach maximum available current is TSS = 2.7*105 * CSS BURST MODE OPERATION Jumper selectable Burst Mode operation provides the tradeoff of low quiescent current at light loads or low ripple voltage at light loads. Figure 2 demonstrates the increased efficiency using Burst Mode at light loads. As the load gets lighter and lighter the effect is increased. At zero load, the quiescent current of the IC is reduced to only 100µA with Burst Mode enabled. The effect of Burst Mode ripple current at light loads is shown in Figure 7. Extremely low, light load ripple voltage can be achieved by disabling Burst Mode. 12VIN 100% 90% 80% EFFICIENCY 70% Burst_En ON 60% 50% 40% 4VIN 30% 20% Burst_En OFF 10% 0% 0.1 1 10 100 1k LOAD CURRENT (mA) Figure 2. DC527 Typical Efficiency (TA = 25°C) 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE 500 MAXIMUM LOAD CURRENT (mA) 450 BUCK 400 350 300 CONTINUOUS INDUCTOR CURRENT 250 BUCK/BOOST 200 150 100 DISCONTINUOUS INDUCTOR CURRENT 50 0 0 5 10 15 20 25 30 35 40 45 50 55 60 VIN (V) Figure 3. DC527 Maximum Load Current is Typically 400mA to 300mA in Buck Mode and 125mA to 200mA in Bridged Mode (Buck and Boost). Figure 4. DC527 Output Voltage Ripple in Bridged Mode (IOUT = 125mA, VIN = 4V, VOUT = 5V, TA = 25°C) CH1 is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L 4 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE Figure 5. DC527 Output Voltage Ripple in Buck Mode (IOUT = 400mA, VIN = 12V, VOUT = 5V, TA = 25°C) CH1 is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L Figure 6. DC527 Output Voltage Ripple Buck Mode (IOUT = 300mA, VIN = 48V, VOUT = 5V, TA = 25°C) CH1 is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L 5 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE Figure 7. DC527 Output Voltage Ripple Burst Mode at Light Load with Burst Mode (IOUT = 5mA, VIN = 12V, VOUT = 5V, TA = 25°C) CH1 is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L Figure 8. DC527 Step Load Response (IOUT = 100mA to 300mA, VIN = 12V, TA = 25°C, VOUT = 5V) CH2 is VOUT ripple, CH4 is IOUT 6 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE Figure 9. DC527 VOUT Soft Start-Up with 10nF CSS (RLOAD = 12.5Ω, VIN = 12V, TA = 25°C) CH2 is VOUT, CH1 is VSW_H 7 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527 STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE 8 5 4 3 2 1 REVISION HISTORY LTC CONFIDENTIAL - For Customer Use Only ECO REV DESCRIPTION DATE PROTO 6 APPROVED 06/09/03 VOUT D 2 D D1 D3 B160 1N4148WS L1 100uH 0.1uF D2 3 CDRH6D28-101 4 + C9 4V to 60V VOUT 13 VBIAS 12 [1] D4 1 1 3 C7 6 VC TP2 C6 10nF Css C3 R1 68k 330pF 5 VFB 7 SGND4 SS SGND3 10 BURST_EN PWRGND GND + C5 R2 14 R3 100k 1% LOAD CURRENT TABLE C4 1nF B UNLESS OTHERWISE SPECIFIED DIMENSIONS ARE IN INCHES TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL PER ASME Y14.5M -1994 NOTES: UNLESS OTHERWISE SPECIFIED, [1] DO NOT INSTALL; C9, C10 A THIRD ANGLE PROJECTION CONTRACT NO. APPROVALS DRAWN MEI C 47uF 10V 305k 16 SHDN SGND2 11 5V@400mA SEE LOAD CURRENT TABLE TP6 2 1N4148WS 0.1uF 2 JP1 TP4 VOUT C10 B120 BURST_EN ON OFF LT3433EFE 9 SHDN SW_L 15 U1 SGND1 GND C2 2.2uF 100V R5 100k [1] VIN 8 C VIN BOOST 1 VIN TP3 SW_H 2 TP1 VOUT 1 C1 DATE 05-30-02 CHECKED TECHNOLOGY TITLE APPROVED VIN IOUT (MAX) 4V 125mA 12V 400mA 24V 360mA 48V 340mA B 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 SCH, LT3433EFE STEP-UP/ STEP-DOWN CONVERTER WITH BURST MODE A ENGINEER DESIGNER SIZE CAGE CODE DO NOT SCALE DRAWING 5 4 Monday, June 23, 2003 3 SCALE: NONE DWG NO REV 6 DC527A A FILENAME: 527A-6.DSN 2 SHEET 1 1 OF 1 Linear Technology Corporation LT3433EFE Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Qty 1 1 1 1 1 1 1 0 1 1 2 1 1 1 1 1 1 0 5 1 1 Ref C1 C2 C3 C4 C5 C6 C7 C9,C10 D1 D2 D4,D3 JP1 L1 R1 R2 R3 R5 R6 TP1,TP2,TP3,TP4,TP6 U1 JP1 Parts List Desc CAP, X7R 0.1uF 16V 10% 0603 CAP, X7R 2.2uF 100V 10% 1812 CAP, NPO 330pF 50V 5% 0402 CAP, X7R 1000pFuF 50V 10% 0603 CAP, TANT 47uF 10V 20% 6032 CAP, X7R 0.01uF 100V 10% 0603 CAP, X7R 0.1uF 16V 10% 0805 DO NOT STUFF DIODE, B160 DIODE, B120 DIODE, SWITCHING HEADER, 3PIN, 2mm IND, 100uH RES, 68k OHMS 5% 1/16W 0603 RES, 305k OHMS 1% 1/16W 0402 RES, 100k OHMS 1% 1/16W 0402 RES, 100k OHMS 1% 1/16W 0603 DO NOT STUFF TURRET IC, LT3433EFE SHUNT, 2PIN, 2mm 1 of 1 DC527A Rev 6 6/24/2003 Manufacturer / Part # AVX 0603YC104KAT TDK C4332X7R2A225K AVX 04025C331JAT AVX 06035C102KAT AVX TPSC476M010R0350 AVX 06031C103KAT AVX 0805YC104KAT1A OPTION DIODES INC. B160 DIODES INC. B120 DIODES INC. 1N4148WS COMM CON 2802S-03G2 SUMIDA CDRH6D28-101 AAC CR16-683JM AAC CR05-3053FM AAC CR05-1003FM AAC CR16-1003FM NONE MILL-MAX-2501-2 LINEAR TECH LT3433EFE COMM CON CCIJ2MM-138G