QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 519 1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER LT1940 DESCRIPTION Demonstration circuit 519 is a 1.1MHz dual step-down DC/DC switching converter using the LT1940. The LT1940 features fast switching speed, two 1.6A internal power switches, and a wide input voltage range, making it a versatile and powerful IC that fits easily into space-constrained applications and removes the need for two separate dc/dc converters in dual output step-down applications. The constant 1.1MHz switching frequency allows for the use of tiny, surface mount external components. The current-mode control topology yields fast transient response and good loop stability, requiring a minimum number of external compensation components and allowing the use of ceramic input and output capacitors. The anti-phase switching and single-IC solution require the use of only a single input capacitor. The low resistance internal 2A power switches (0.21) maintain high efficiencies (as high as 90%) over a wide range of input voltages and loads. Its 30A shutdown current (activated via the Run/SS pins) extends battery life. The wide VIN range of the LT1940 allows step-down configurations with up to 25V input. The demonstration board has two circuits to demonstrate both the small space that the monolithic dual step-down converter can achieve with high currents and a single IC as well as the versatility and maximum power output of the IC. The circuit demonstrating smallest size generates 3.3V at up to 1A and 1.8V at up to 1A output from a 4.8V-14V input. The larger, more versatile circuit generates 5V at up to 1.4A and 3.3V at up to 1.4A output from a separate 6.8V to 25V input. The two circuits are completely isolated from each other and can be run simultaneously or independently. The versatile circuit has options for changing the boost diodes for highest efficiency under different output voltage conditions. The feedforward capacitors and noise-reduction capacitors on the Vc pins further increase the parts count on the versatile board, yet they improve the transient response and give the ability to optimize loop compensation under various conditions. This board is designed for applications that require two step-down supplies with up to 1.4A load current in a small board space with low cost and low parts count as well as simple circuit design. The high current, onboard, dual monolithic switches eliminate the need for external switches. The use of ceramic capacitors in this circuit not only demonstrates small size and low cost, but the advantage of current-mode control in step-down applications with a simple compensation network and a feedforward capacitor for more rugged stability and excellent transient response. Design files for this circuit board are available. Call the LTC factory. Table 1. Typical Performance (TA = 25C) for Small Dual Step-Down Converter (VOUT1=3.3V and VOUT2=1.8V) PARAMETER VALUE VIN 4.8V to 14V VOUT1 3.3V VOUT2 1.8V VOUT1 Load Current 1A(max) VOUT2 Load Current 1A(max) Efficiency 80% at 1A load current (VOUT1 and VOUT2) 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 519 1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER Table 2. Typical Performance (TA = 25C) for Customizable Dual Step-Down Converter (VOUT1=5.0V and VOUT2=3.3V) Parameter Value VIN 6.8V to 25V VOUT1 5.0V 3.3V VOUT1 Load Current 1.4A(max) VOUT2 Load Current 1.4A(max) Efficiency 84% at 1A load current (VOUT1 and VOUT2) 100% 100% 90% 90% 80% 80% 70% 70% EFFICIENCY EFFICIENCY VOUT2 60% VIN = 5V 50% VIN = 8V 40% VIN = 12V 30% 60% VIN = 8V 50% VIN = 12V 40% VIN = 18V 30% 20% 20% 10% 10% 0% 0% 0 200 400 600 800 0 1.0k V OUT1 LOAD CURRENT (mA) VOUT2 LOAD CURRENT = 1A V OUT1 LOAD CURRENT (mA) VOUT2 LOAD CURRENT = 1A Figure 3. Typical Efficiency of Demo Circuit 519 LT1940, Customizable Dual Step-Down VOUT1=5.0V, VOUT2=3.3V 100% 100% 90% 90% 80% 80% 70% 70% EFFICIENCY EFFICIENCY Figure 1. Typical Efficiency of Demo Circuit 519 LT1940, Small Dual Step-Down VOUT1=3.3V, VOUT2=1.8V 60% VIN = 5V 50% VIN = 8V 40% VIN = 12V 30% 200 400 600 800 1.0k 1.2k 1.4k 60% VIN = 8V 50% VIN = 12V 40% VIN = 18V 30% 20% 20% 10% 10% 0% 0% 0 200 400 600 800 1.0k V OUT2 LOAD CURRENT (mA) VOUT1 LOAD CURRENT = 1A Figure 2. Typical Efficiency of Demo Circuit 519 LT1940, Small Dual Step-Down VOUT1=3.3V, VOUT2=1.8V 0 200 400 600 800 1.0k 1.2k 1.4k V OUT2 LOAD CURRENT (mA) VOUT1 LOAD CURRENT = 1A Figure 4. Typical Efficiency of Demo Circuit 519 LT1940, Customizable Dual Step-Down VOUT1=5.0V, VOUT2=3.3V 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 519 1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER QUICK START PROCEDURE Demonstration circuit 519 is easy to set up to evaluate the performance of the LT1940. Refer to Figure 5 for proper measurement equipment setup and follow the procedure below: + - + - LOAD + - 1. Connect the 4.8V-14V or 6.8V-25V input power sup- + + and verify that the output voltage is either 3.3V and 1.8V (small, top circuit) or 5V and 3.3V (larger, bottom circuit) for the circuit to which the input supply is connected. + - + + - - 2. After all connections are made, turn on input power - ply to the VIN and GND terminals on the board corresponding to the small, top circuit or the larger, customizable, bottom circuit. Each circuit is powered separately from its own VIN and GND terminals. LOAD - - 3. The Run/SS and Power Good functions are optional - - LOAD + - + + + + + - - and their terminals can be left floating (disconnected) if their functions are not being used. Connecting a Run/SS terminal to the GND terminal will disable the corresponding output. - + + + - - + - LOAD Figure 5. Proper Measurement Equipment Setup 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 519 1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER CUSTOMIZING THE BOARD The components used in the demonstration circuits are optimized for wide input voltage ranges. Nevertheless, the bandwidths can be increased for more specific input voltages, such as 12V10% or 5V10%, by changing the VC components, the noise filter caps, the feedforward caps, and the output capacitors. The adjustable feedback resistors allow the output voltages to be customized. The boost diodes D8 and D11 on the small circuit are the only boost diode options on that circuit for minimal space considerations. The anode of D8 is connected to Vout1 (3.3V). The anode of D11 is connected to Vin (4.8V to 14V) since Vout2 is 1.8V and is below 3.0V. The minimum boost voltage required for the internal power switch is 3.0V and that can usually be taken directly from a 3.3V output or greater. However, if the output voltage is below 3.3V, in order to maintain high efficiency, the boost diode should get its voltage from either the input (which is less efficient than a greater than 3.3V output) or another source such as the other output on the board (if it is greater than 3.3V). Since there is not space to make these changes in boost diode location on the small circuit, D8 and D11 should always be used (not customized) and Vout1 should always be 3.3V or greater and Vout 2 can be less than 3.3V. If Vout2 is 3.3V or greater, the small circuit, with D11 installed connecting to the input, will not be as efficient as it could be if D11 was instead connected to Vout2. The larger, versatile circuit has pad placements built-in for customized output voltages of all acceptable levels. D1 and D3 are connected to Vout1 (5V) and Vout2 (3.3V) respectively since they are both 3.3V or greater and they provide enough boost to saturate the high-side NPN power switches. However, if either output voltage is customized to less than 3.3V, D1 can be removed and replaced by stuffing D2 with the same part. D3 can be removed and replaced by stuffing D4 with the same part. Both D2 and D4 connect the boost to Vin. Additionally, D5 provides a way to replace D3 with a boost diode that is connected to Vout1 in case Vout1 is 3.3V or greater and Vout2 is less than 3.3V. Make sure that the boost capacitors (C27, C15, C1, C2) have voltage ratings greater than or equal to the output voltage for applications where the boost diode is connected to the output. However, the boost capacitor must have a voltage rating greater than the input voltage whenever the boost diode is connected to the input. 4 5 4 3 2 1 REVISION HISTORY ECO REV > DESCRIPTION DATE PROTO 3 APPROVED 05-24-02 D D L1 5.3uH TP1 CDRH5 D28-5R3 D2 [1] VOUT1 VOUT1 D1 CMDSH-3 R2 Cff1 78.7k 62pF SOD323 C3 10uF 6.3V C10 5V @ 1.4A 0.1uF R1 24.9k R7 100K GND TP9 U1 LT1940EFE 0.1uF 1 2 C 3 B130 VIN 4 VIN TP3 CIN 4.7uF X7R 25V 6.8V to 25V GND TP8 C9 0.1uF 5 6 D7 C2 0.1uF 8 FB1 SW1 Vc1 VIN0 PG1 VIN1 RUN/SS1 VIN2 RUN/SS2 VIN3 PG2 SW2 Vc2 BOOST2 FB2 16 100pF C5 R6 22k 15 C 1000pF 14 TP4 PG1 13 TP5 Run/SS1 12 TP6 Run/SS2 11 TP7 PG2 10 C7 R5 22k 9 1000pF 17 B130 7 BOOST1 GND C1 D6 C6 C8 C12 C1 3 0.1uF 0.1uF 100pF D5 [1] R8 100K VOUT1 GND R3 D4 TP10 D3 B [1] CMDSH-3 SOD323 L2 4.1uH R4 24.9k Cff2 41.2k 62pF B VOUT2 VOUT2 TP2 CDRH5 D18-4R1 C4 10uF 6.3V C11 3.3V @ 1.4A 0.1uF NOTES: UNLESS OTHERWISE SPECIFIED, [1] DO NOT STUFF. UNLESS OTHERWISE SPECIFIED DIMENSIONS ARE IN INCHES TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL PER ASME Y14.5M -1994 A THIRD ANGLE PROJECTION CONTRACT NO. APPROVALS DRAWN MEI CHECKED DATE 05-24-02 TECHNOLOGY TITLE APPROVED 1630 McCarthyBlvd. Milpitas, CA 95035 Phone: (408)432 -1900 Fax: (408)434-0507 A SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER ENGINEER DESIGNER SIZE CAGE CODE Cust om DO NOT SCALE DRAWING 5 4 3 Monday, July 22, 2002 SCALE:NONE 2 DWG NO REV 3 DC5 19A FILENAME: 519A-3 .DSN SHEET 1 1 OF 2 5 4 3 2 1 REVISION HISTORY ECO REV > DESCRIPTION DATE PROTO 3 APPROVED 05-24-02 D D L3 2.7uH VOUT1 VOUT1 TP11 1008PS-272M R10 D8 CMDSH-3 C1 6 10uF 6.3V 41.2k C2 3 3.3V @ 1A 0.1uF R9 SOD323 24.9k R15 100K GND TP19 U2 LT1940EFE 2 3 UPS120 VIN 4 VIN TP13 CIN2 4.7uF X5R 16V 4.8V to 14V 1 GND 5 6 D14 UPS120 7 C15 0.1uF 8 FB1 SW1 Vc1 VIN0 PG1 VIN1 RUN/SS1 VIN2 RUN/SS2 VIN3 PG2 SW2 Vc2 BOOST2 FB2 16 C1 8 R1 4 22k C 15 1000pF 14 TP14 PG1 13 TP15 Run/SS1 12 TP16 Run/SS2 11 TP17 PG2 10 C2 0 R1 3 22k 9 1500pF C2 5 C26 0.1uF 0.1uF 17 TP18 C22 0.1uF BOOST1 GND C27 0.1uF D13 C R16 100K D1 1 GND R1 1 TP20 CMDSH-3 B R12 SOD323 24.9k B 12.4k L4 1.8uH VOUT2 VOUT2 TP12 1008PS-182M C1 7 22uF 6.3V C2 4 1.8V @ 1A 0.1uF NOTES: UNLESS OTHERWISE SPECIFIED, [1] DO NOT STUFF. UNLESS OTHERWISE SPECIFIED DIMENSIONS ARE IN INCHES TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL PER ASME Y14.5M -1994 A THIRD ANGLE PROJECTION CONTRACT NO. APPROVALS DRAWN MEI CHECKED DATE 05-24-02 TECHNOLOGY TITLE APPROVED 1630 McCarthyBlvd. Milpitas, CA95035 Phone: (408)43 2-1900 Fax: (408)434-0507 A SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER ENGINEER DESIGNER SIZE CAGE CODE Cust om DO NOT SCALE DRAWING 5 4 3 Monday, July 22, 2002 SCALE:NONE 2 DWG NO REV 3 DC5 19A FILENAME: 519A-3 .DSN SHEET 1 2 OF 2 5 4 3 2 1 REVISION HISTORY ECO REV > DESCRIPTION DATE RELEASE 3 APPROVED 10/31/02 D D L1 5.3uH TP1 CDRH5 D28-5R3 D2 [1] VOUT1 VOUT1 D1 CMDSH-3 R2 Cff1 75.0k 62pF SOD323 C3 10uF 6.3V C10 5V @ 1.4A 0.1uF R1 24.9k R7 100K GND TP9 U1 LT1940EFE 0.1uF 1 2 C 3 B130 VIN 4 VIN TP3 CIN 4.7uF X7R 25V 6.8V to 25V GND TP8 C9 0.1uF 5 6 D7 C2 0.1uF 8 FB1 SW1 Vc1 VIN0 PG1 VIN1 RUN/SS1 VIN2 RUN/SS2 VIN3 PG2 SW2 Vc2 BOOST2 FB2 16 100pF C5 R6 22k 15 C 1000pF 14 TP4 PG1 13 TP5 Run/SS1 12 TP6 Run/SS2 11 TP7 PG2 10 C7 R5 22k 9 1000pF 17 B130 7 BOOST1 GND C1 D6 C6 C8 C12 C1 3 0.1uF 0.1uF 100pF D5 [1] R8 100K VOUT1 GND R3 D4 TP10 D3 B [1] CMDSH-3 SOD323 L2 4.1uH R4 24.9k Cff2 41.2k 62pF B VOUT2 VOUT2 TP2 CDRH5 D18-4R1 C4 10uF 6.3V C11 3.3V @ 1.4A 0.1uF NOTES: UNLESS OTHERWISE SPECIFIED, [1] DO NOT STUFF. UNLESS OTHERWISE SPECIFIED DIMENSIONS ARE IN INCHES TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL PER ASME Y14.5M -1994 A THIRD ANGLE PROJECTION CONTRACT NO. APPROVALS DRAWN MEI CHECKED DATE 05-24-02 TECHNOLOGY TITLE APPROVED 1630 McCarthyBlvd. Milpitas, CA 95035 Phone: (408)432 -1900 Fax: (408)434-0507 A SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER ENGINEER DESIGNER SIZE CAGE CODE Cust om DO NOT SCALE DRAWING 5 4 3 Thursday, October 31, 2002 SCALE:NONE 2 DWG NO REV 3 DC5 19A FILENAME: 519A-3 .DSN SHEET 1 1 OF 2 5 4 3 2 1 REVISION HISTORY ECO REV > DESCRIPTION DATE RELEASE 3 APPROVED 10/31/02 D D L3 2.7uH VOUT1 VOUT1 TP11 1008PS-272M R10 D8 CMDSH-3 C1 6 10uF 6.3V 41.2k C2 3 3.3V @ 1A 0.1uF R9 SOD323 24.9k R15 100K GND TP19 U2 LT1940EFE 2 3 UPS120 VIN 4 VIN TP13 CIN2 4.7uF X5R 16V 4.8V to 14V 1 GND 5 6 D14 UPS120 7 C15 0.1uF 8 FB1 SW1 Vc1 VIN0 PG1 VIN1 RUN/SS1 VIN2 RUN/SS2 VIN3 PG2 SW2 Vc2 BOOST2 FB2 16 C1 8 R1 4 22k C 15 1000pF 14 TP14 PG1 13 TP15 Run/SS1 12 TP16 Run/SS2 11 TP17 PG2 10 C2 0 R1 3 22k 9 1500pF C2 5 C26 0.1uF 0.1uF 17 TP18 C22 0.1uF BOOST1 GND C27 0.1uF D13 C R16 100K D1 1 GND R1 1 TP20 CMDSH-3 B R12 SOD323 24.9k B 11.0k L4 1.8uH VOUT2 VOUT2 TP12 1008PS-182M C1 7 22uF 6.3V C2 4 1.8V @ 1A 0.1uF NOTES: UNLESS OTHERWISE SPECIFIED, [1] DO NOT STUFF. UNLESS OTHERWISE SPECIFIED DIMENSIONS ARE IN INCHES TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL PER ASME Y14.5M -1994 A THIRD ANGLE PROJECTION CONTRACT NO. APPROVALS DRAWN MEI CHECKED DATE 05-24-02 TECHNOLOGY TITLE APPROVED 1630 McCarthyBlvd. Milpitas, CA95035 Phone: (408)43 2-1900 Fax: (408)434-0507 A SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER ENGINEER DESIGNER SIZE CAGE CODE Cust om DO NOT SCALE DRAWING 5 4 3 Thursday, October 31, 2002 SCALE:NONE 2 DWG NO REV 3 DC5 19A FILENAME: 519A-3 .DSN SHEET 1 2 OF 2 Linear Technology Corporation LT1940EFE Item 1 2 3 4 Qty 1 1 2 8 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 2 2 2 0 1 1 1 1 2 4 0 2 2 1 1 1 1 2 1 1 2 2 2 1 1 2 2 20 2 Ref CIN CIN2 Cff1,Cff2 C1,C2,C9,C12,C13,C15,C22, C27 C4,C3 C5,C7 C6,C8 C10,C11,C23,C24 C16 C17 C18 C20 C26,C25 D1,D3,D8,D11 D2,D4,D5 D6,D7 D14,D13 L1 L2 L3 L4 R1,R3 R2 R4 R6,R5 R7,R8 R11,R9 R10 R12 R13,R14 R15,R16 TP1-TP20 U1,U2 Parts List DC519A Rev 3 7/25/2002 Desc CAP, X7R 4.7uF 25V 20% 1210 CAP, X5R 4.7uF 16V 10% 1206 CAP, NPO 62pF 25V 5% 0603 CAP, X7R 0.1uF 16V 10% 0603 Part Number TDK C3225X7R1E475M TAIYO YUDEN EMK316BJ475KL AVX 06033A620JAT AVX 0603YC104KAT CAP, X5R 10uF 6.3V 20% 1206 CAP, X7R 1000pF 50V 5% 0603 CAP, NPO 100pF 50V 5% 0603 CAP, X7R 0.1uF 16V 10% 0603 CAP, X5R 10uF 6.3V 10% 0805 CAP, X5R 22uF 6.3V 10% 1210 CAP, X7R 1000pF 50V 5% 0402 CAP, X7R 1500pF 50V 5% 0402 CAP, X5R 0.1uF 10V 10% 0402 DIODE, CMDSH-3 SOD323 DO NOT STUFF DIODE, B130 SCHOTTKY RECTIFIER 1A DIODE, SCHOTTKY RECTIFIER 1A UPS120 IND, 5.3uH IND, 4.1uH IND, 2.7uH IND, 1.8uH RES, 24.9k OHMS 1% 1/16W 0603 RES, 78.7k OHMS 1% 1/16W 0603 RES, 41.2k OHMS 1% 1/16W 0603 RES, 22K OHMS 5% 1/16W 0603 RES, 100K OHMS 5% 1/16W 0603 RES, 24.9k OHMS 1% 1/16W 0402 RES, 41.2k OHMS 1% 1/16W 0402 RES, 12.4k OHMS 1% 1/16W 0402 RES, 22K OHMS 5% 1/16W 0402 RES, 100K OHMS 5% 1/16W 0402 TURRETS IC, LT1940EFE DUAL STEP-DOWN DC/DC CONVERTER TAIYO YUDEN JMK316BJ106ML-T AVX 06035C102JAT2A AVX 06035A101JAT AVX 0603YC104KAT OPTION TDK C2012X5R0J106M TDK C3225X5R0J226M AVX 04025C102JAT AVX 04025C152KAT AVX 0402ZD104KAT CENTRAL CMDSH-3 OPTION DIODES INC. B130 MICROSEMI UPS120 SUMIDA CDRH5D28-5R3 SUMIDA CDRH5D18-4R1NC COILCRAFT 1008PS-272M COILCRAFT 1008PS-182M AAC CR16-2492FM AAC CR16-7872FM AAC CR16-4122FM AAC CR16-223JM AAC CR16-104JM AAC CR05-2492FM AAC CR05-4122FM AAC CR05-1242FM AAC CR05-223JM AAC CR05-104JM MILL-MAX-2501-2 LINEAR TECH LT1940EFE 1 of 1