LT1940
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LT1940 - LT1940
QUICK START GUIDE DEMONSTRATION CIRCUIT
1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER
LT1940 DESCRIPTION
Demonstration circuit 1.1MHz dual step-down DC/DC switching converter using LT1940. LT1940 features fast switching speed, 1.6A internal power switches, wide input voltage range, making versatile powerful that fits easily into space-constrained applications removes need separate dc/dc converters dual output step-down applications. constant 1.1MHz switching frequency allows tiny, surface mount external components. current-mode control topology yields fast transient response good loop stability, requiring minimum number external compensation components allowing ceramic input output capacitors. anti-phase switching single-IC solution require only single input capacitor. resistance internal power switches (0.21) maintain high efficiencies high 90%) over wide range input voltages loads. 30µA shutdown current (activated Run/SS pins) extends battery life. wide range LT1940 allows step-down configurations with input. demonstration board circuits demonstrate both small space that monolithic dual step-down converter achieve with high currents single well versatility maximum power output circuit demonstrating smallest size generates 3.3V 1.8V output from 4.8V-14V input. larger, more versatile circuit generates 1.4A 3.3V 1.4A output from separate 6.8V input. circuits completely isolated from each other simultaneously independently. versatile circuit options changing boost diodes highest efficiency under different output voltage conditions. feedforward capacitors noise-reduction capacitors pins further increase parts count versatile board, they improve transient response give ability optimize loop compensation under various conditions. This board designed applications that require step-down supplies with 1.4A load current small board space with cost parts count well simple circuit design. high current, onboard, dual monolithic switches eliminate need external switches. ceramic capacitors this circuit only demonstrates small size cost, advantage current-mode control step-down applications with simple compensation network feedforward capacitor more rugged stability excellent transient response. Design files this circuit board available. Call factory.
Table Typical Performance 25°C) Small Dual Step-Down Converter (VOUT1=3.3V VOUT2=1.8V)
PARAMETER VOUT1 VOUT2 VOUT1 Load Current VOUT2 Load Current Efficiency VALUE 4.8V 3.3V 1.8V 1A(max) 1A(max) load current (VOUT1 VOUT2)
QUICK START GUIDE DEMONSTRATION CIRCUIT
1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER
Table Typical Performance 25°C) Customizable Dual Step-Down Converter (VOUT1=5.0V VOUT2=3.3V)
Parameter VOUT1 VOUT2 VOUT1 Load Current VOUT2 Load Current Efficiency Value 6.8V 5.0V 3.3V 1.4A(max) 1.4A(max) load current (VOUT1 VOUT2)
100%
EFFICIENCY
100%
EFFICIENCY
1.0k
1.0k 1.2k 1.4k OUT1 LOAD CURRENT (mA) VOUT2 LOAD CURRENT
OUT1 LOAD CURRENT (mA) VOUT2 LOAD CURRENT
Figure Typical Efficiency Demo Circuit LT1940, Small Dual Step-Down VOUT1=3.3V, VOUT2=1.8V
100%
EFFICIENCY
Figure Typical Efficiency Demo Circuit LT1940, Customizable Dual Step-Down VOUT1=5.0V, VOUT2=3.3V
100%
EFFICIENCY
1.0k
1.0k 1.2k 1.4k OUT2 LOAD CURRENT (mA) VOUT1 LOAD CURRENT
OUT2 LOAD CURRENT (mA) VOUT1 LOAD CURRENT
Figure Typical Efficiency Demo Circuit LT1940, Small Dual Step-Down VOUT1=3.3V, VOUT2=1.8V
Figure Typical Efficiency Demo Circuit LT1940, Customizable Dual Step-Down VOUT1=5.0V, VOUT2=3.3V
QUICK START GUIDE DEMONSTRATION CIRCUIT
1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER
QUICK START PROCEDURE
Demonstration circuit easy evaluate performance LT1940. Refer Figure proper measurement equipment setup follow procedure below:
Connect 4.8V-14V 6.8V-25V input power sup+
LOAD
Run/SS Power Good functions optional
their terminals left floating (disconnected) their functions being used. Connecting Run/SS terminal terminal will disable corresponding output.
LOAD
Figure Proper Measurement Equipment Setup
verify that output voltage either 3.3V 1.8V (small, circuit) 3.3V (larger, bottom circuit) circuit which input supply connected.
After connections made, turn input power
LOAD
terminals board corresponding small, circuit larger, customizable, bottom circuit. Each circuit powered separately from terminals.
LOAD
QUICK START GUIDE DEMONSTRATION CIRCUIT
1.1MHZ DUAL STEP-DOWN DC/DC CONVERTER
CUSTOMIZING BOARD components used demonstration circuits optimized wide input voltage ranges. Nevertheless, bandwidths increased more specific input voltages, such 12V±10% 5V±10%, changing components, noise filter caps, feedforward caps, output capacitors. adjustable feedback resistors allow output voltages customized. boost diodes small circuit only boost diode options that circuit minimal space considerations. anode connected Vout1 (3.3V). anode connected (4.8V 14V) since Vout2 1.8V below 3.0V. minimum boost voltage required internal power switch 3.0V that usually taken directly from 3.3V output greater. However, output voltage below 3.3V, order maintain high efficiency, boost diode should voltage from either input (which less efficient than greater than 3.3V output) another source such other output board greater than 3.3V). Since there space make these changes boost diode location small circuit, should always used (not customized) Vout1 should always 3.3V greater Vout less than 3.3V. Vout2 3.3V greater, small circuit, with installed connecting input, will efficient could instead connected Vout2. larger, versatile circuit placements built-in customized output voltages acceptable levels. connected Vout1 (5V) Vout2 (3.3V) respectively since they both 3.3V greater they provide enough boost saturate high-side power switches. However, either output voltage customized less than 3.3V, removed replaced stuffing with same part. removed replaced stuffing with same part. Both connect boost Vin. Additionally, provides replace with boost diode that connected Vout1 case Vout1 3.3V greater Vout2 less than 3.3V. Make sure that boost capacitors (C27, C15, have voltage ratings greater than equal output voltage applications where boost diode connected output. However, boost capacitor must have voltage rating greater than input voltage whenever boost diode connected input.
REVISION HISTORY
DESCRIPTION PROTO DATE 05-24-02 APPROVED
5.3uH CDRH5 D28-5R3 10uF 6.3V
VOUT1
VOUT1
CMDSH-3
SOD323
78.7k
Cff1 62pF
0.1uF
1.4A
24.9k
100K
LT1940EFE
1000pF 100pF 100K 0.1uF 0.1uF 1000pF 100pF
0.1uF
BOOST1 VIN0 VIN1 VIN2 VIN3 BOOST2
RUN/SS1 RUN/SS2
B130
Run/SS1 Run/SS2
6.8V
4.7uF
B130 0.1uF
0.1uF
VOUT1
TP10
24.9k Cff2 62pF
VOUT2
CMDSH-3
SOD323
4.1uH CDRH5 D18-4R1
41.2k
VOUT2
0.1uF 3.3V 1.4A
10uF 6.3V
NOTES: UNLESS OTHERWISE SPECIFIED, STUFF.
UNLESS OTHERWISE SPECIFIED DIMENSIONS INCHES TOLERANCE ANGLE PLACES PLACES INTERPRET ASME Y14.5M -1994 THIRD ANGLE PROJECTION
CONTRACT APPROVALS
DRAWN CHECKED APPROVED ENGINEER DESIGNER
DATE
05-24-02
TECHNOLOGY
TITLE
1630 McCart yBlvd. Milpitas, Phone: (408)432 Fax: (408)434
SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER
CAGE CODE FILENAME: 519A-3 .DSN SHEET
SIZE Cust
SCALE DRAWING
Monday, July 2002
SCALE:NONE
REVISION HISTORY
DESCRIPTION PROTO DATE 05-24-02 APPROVED
2.7uH 1008PS-272M CMDSH-3
SOD323
VOUT1
VOUT1
TP11
41.2k 24.9k
10uF 6.3V
0.1uF
3.3V
100K
TP19
LT1940EFE 0.1uF
UPS120
BOOST1 VIN0 VIN1 VIN2 VIN3 BOOST2
RUN/SS1 RUN/SS2
1000pF
TP13
TP14 TP15 Run/SS1 TP16 Run/SS2 TP17
4.8V
TP18
CIN2 4.7uF
0.1uF UPS120 0.1uF
1500pF
0.1uF
0.1uF
100K 24.9k
TP20
CMDSH-3
SOD323
1.8uH 1008PS-182M 12.4k
VOUT2
VOUT2
TP12 0.1uF 1.8V
22uF 6.3V
NOTES: UNLESS OTHERWISE SPECIFIED, STUFF.
UNLESS OTHERWISE SPECIFIED DIMENSIONS INCHES TOLERANCE ANGLE PLACES PLACES INTERPRET ASME Y14.5M -1994 THIRD ANGLE PROJECTION
CONTRACT APPROVALS
DRAWN CHECKED APPROVED ENGINEER DESIGNER
DATE
05-24-02
TECHNOLOGY
TITLE
1630 McCart yBlvd. Milpitas, Phone: (408)43- Fax: (408)43
SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER
CAGE CODE FILENAME: 519A-3 .DSN SHEET
SIZE Cust
SCALE DRAWING
Monday, July 2002
SCALE:NONE
REVISION HISTORY
DESCRIPTION RELEASE DATE 10/31/02 APPROVED
5.3uH CDRH5 D28-5R3 10uF 6.3V
VOUT1
VOUT1
CMDSH-3
SOD323
75.0k
Cff1 62pF
0.1uF
1.4A
24.9k
100K
LT1940EFE
1000pF 100pF 100K 0.1uF 0.1uF 1000pF 100pF
0.1uF
BOOST1 VIN0 VIN1 VIN2 VIN3 BOOST2
RUN/SS1 RUN/SS2
B130
Run/SS1 Run/SS2
6.8V
4.7uF
B130 0.1uF
0.1uF
VOUT1
TP10
24.9k Cff2 62pF
VOUT2
CMDSH-3
SOD323
4.1uH CDRH5 D18-4R1
41.2k
VOUT2
0.1uF 3.3V 1.4A
10uF 6.3V
NOTES: UNLESS OTHERWISE SPECIFIED, STUFF.
UNLESS OTHERWISE SPECIFIED DIMENSIONS INCHES TOLERANCE ANGLE PLACES PLACES INTERPRET ASME Y14.5M -1994 THIRD ANGLE PROJECTION
CONTRACT APPROVALS
DRAWN CHECKED APPROVED ENGINEER DESIGNER
DATE
05-24-02
TECHNOLOGY
TITLE
1630 McCart yBlvd. Milpitas, Phone: (408)432 Fax: (408)434
SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER
CAGE CODE FILENAME: 519A-3 .DSN SHEET
SIZE Cust
SCALE DRAWING
Thursday, October 2002 SCALE:NONE
REVISION HISTORY
DESCRIPTION RELEASE DATE 10/31/02 APPROVED
2.7uH 1008PS-272M CMDSH-3
SOD323
VOUT1
VOUT1
TP11
41.2k 24.9k
10uF 6.3V
0.1uF
3.3V
100K
TP19
LT1940EFE 0.1uF
UPS120
BOOST1 VIN0 VIN1 VIN2 VIN3 BOOST2
RUN/SS1 RUN/SS2
1000pF
TP13
TP14 TP15 Run/SS1 TP16 Run/SS2 TP17
4.8V
TP18
CIN2 4.7uF
0.1uF UPS120 0.1uF
1500pF
0.1uF
0.1uF
100K 24.9k
TP20
CMDSH-3
SOD323
1.8uH 1008PS-182M 11.0k
VOUT2
VOUT2
TP12 0.1uF 1.8V
22uF 6.3V
NOTES: UNLESS OTHERWISE SPECIFIED, STUFF.
UNLESS OTHERWISE SPECIFIED DIMENSIONS INCHES TOLERANCE ANGLE PLACES PLACES INTERPRET ASME Y14.5M -1994 THIRD ANGLE PROJECTION
CONTRACT APPROVALS
DRAWN CHECKED APPROVED ENGINEER DESIGNER
DATE
05-24-02
TECHNOLOGY
TITLE
1630 McCart yBlvd. Milpitas, Phone: (408)43- Fax: (408)43
SCH, LT1940EFE 1.1MHz DUAL STEP-DOWN DC/DC CONVERTER
CAGE CODE FILENAME: 519A-3 .DSN SHEET
SIZE Cust
SCALE DRAWING
Thursday, October 2002 SCALE:NONE
Linear Technology Corporation LT1940EFE Item CIN2 Cff1,Cff2 C1,C2,C9,C12,C13,C15,C22, C4,C3 C5,C7 C6,C8 C10,C11,C23,C24 C26,C25 D1,D3,D8,D11 D2,D4,D5 D6,D7 D14,D13 R1,R3 R6,R5 R7,R8 R11,R9 R13,R14 R15,R16 TP1-TP20 U1,U2
Parts List
DC519A 7/25/2002 Part Number C3225X7R1E475M TAIYO YUDEN EMK316BJ475KL 06033A620JAT 0603YC104KAT TAIYO YUDEN JMK316BJ106ML-T 06035C102JAT2A 06035A101JAT 0603YC104KAT OPTION C2012X5R0J106M C3225X5R0J226M 04025C102JAT 04025C152KAT 0402ZD104KAT CENTRAL CMDSH-3 OPTION DIODES INC. B130 MICROSEMI UPS120 SUMIDA CDRH5D28-5R3 SUMIDA CDRH5D18-4R1NC COILCRAFT 1008PS-272M COILCRAFT 1008PS-182M CR16-2492FM CR16-7872FM CR16-4122FM CR16-223JM CR16-104JM CR05-2492FM CR05-4122FM CR05-1242FM CR05-223JM CR05-104JM MILL-MAX-2501-2 LINEAR TECH LT1940EFE
Desc CAP, 4.7uF 1210 CAP, 4.7uF 1206 CAP, 62pF 0603 CAP, 0.1uF 0603 CAP, 10uF 6.3V 1206 CAP, 1000pF 0603 CAP, 100pF 0603 CAP, 0.1uF 0603 CAP, 10uF 6.3V 0805 CAP, 22uF 6.3V 1210 CAP, 1000pF 0402 CAP, 1500pF 0402 CAP, 0.1uF 0402 DIODE, CMDSH-3 SOD323 STUFF DIODE, B130 SCHOTTKY RECTIFIER DIODE, SCHOTTKY RECTIFIER UPS120 IND, 5.3uH IND, 4.1uH IND, 2.7uH IND, 1.8uH RES, 24.9k OHMS 1/16W 0603 RES, 78.7k OHMS 1/16W 0603 RES, 41.2k OHMS 1/16W 0603 RES, OHMS 1/16W 0603 RES, 100K OHMS 1/16W 0603 RES, 24.9k OHMS 1/16W 0402 RES, 41.2k OHMS 1/16W 0402 RES, 12.4k OHMS 1/16W 0402 RES, OHMS 1/16W 0402 RES, 100K OHMS 1/16W 0402 TURRETS LT1940EFE DUAL STEP-DOWN DC/DC CONVERTER
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