Linear Technology LTC3124 Quick setup guide

1
dc1859afa
DEMO MANUAL DC1859A
DESCRIPTION
LTC3124
Dual Phase Synchronous
Step-Up DC/DC Converter
Demonstration circuit 1859A is a dual phase single out-
put DC/DC boost converter featuring the LT C
®
3124. The
DC1859A operates over 1.8V to 5.5V input and generates
12V at up to 1.5A from a 5V input. The maximum output
current for a 1.8V input is 750mA. Also, the LTC3124 has
a2% precise voltage reference, which can generate an
output voltage with 2.2% tolerance if 0.1% voltage divider
resistors are used. The 1MHz switching frequency opera-
tion results in small and efficient circuit. The converter
operates with only one phase in Burst Mode
®
operation L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
PERFORMANCE SUMMARY
and achieves over 90% efficiency with a 100mA load. The
demonstration circuit can be easily modified to generate
different output voltages.
The DC1859 has small circuit footprint. It is a high perfor-
mance and cost effective solution for generating output
voltages up to 15V from inputs as low as 1.8V.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1859A
Specifications are at TA= 25°C
PARAMETER CONDITION MIN TYP MAX UNITS
Minimum Input Voltage IOUT = 0A to 0.75A 1.8 V
Maximum Input Voltage IOUT = 0A to 1.5A 5.5 V
VOUT VIN = 1.8V to 5.5V, IOUT = 0A 12 V ±4%
Output Voltage Ripple VIN = 5V, IOUT = 1.5A 100 mVP-P
Nominal Switching Frequency 1 MHz

2
dc1859afa
DEMO MANUAL DC1859A
QUICK START PROCEDURE
Demonstration circuit 1859 is easy to set up to evaluate
the performance of the LTC3124. For proper measure-
ment equipment setup refer to Figure 1 and follow the
procedure below:
NOTE: When measuring the input or output voltage ripple,
care must be taken to minimize the length of oscilloscope
probe ground lead. Measure the input or output voltage
ripple by connecting the probe tip directly across the VIN
or VOUT and GND terminals as shown in Figure 2.
1. With power off, connect the input power supply to VIN
and GND.
2. Keep the load set to 0A or disconnected.
3. Turn the input power source on and slowly increase the
input voltage. Be careful not to exceed 5.5V.
NOTE: Make sure that the input voltage VIN does not
exceed 5.5V.
4. Set the input voltage to 5V and check for the proper
output voltage of 12V. If there is no output, temporarily
disconnect the load to make sure that the load is not
set too high.
5. Once the proper output voltage is established, adjust
the load and observe the output voltage regulation,
ripple voltage, efficiency and other parameters.
Figure 1. Proper Measurement Equipment Setup

3
dc1859afa
DEMO MANUAL DC1859A
+ –
VOUT GND
COUT
Figure 2. Measuring Input or Output Ripple
QUICK START PROCEDURE
Changing the Output Voltage
To change the output voltage from the programmed 12V,
change the voltage divider resistors connected to LTC3124
FB pin (see the schematic on page 5).
Converter Output Current
The DC1859 output current capability depends on the
input voltage. Typical performance of DC1859A is shown
in Figure 3. As can be seen from Figure 3, the maximum
output current is 800mA with 2.6V input and 2A with 5V
input. The efficiency is high at light loads thanks to phase
shedding in BURST mode. By disabling one phase the
related switching losses are reduced and the efficiency
is maximized.
Figure 3. The Efficiency Is Maximized for Light Loads by
Shedding One Phase in Burst Mode Operation. The Efficiency Is
Over 90% at Higher Loads and It Reaches 92% at 800mA Load
Output Load Step Response
The load step response of DC1859A is dependent on the
amount and type of output caps used. If higher load steps
need to be handled more output capacitance can be added
in order to keep the voltage transients at the desired level.
The load step transients are shown in Figure 4. Other types
of low ESR and high value capacitors can be used if space
is available to reduce load transients to desired level.
Figure 4. The LTC3124 Has Excellent Load Step Response with
Small Output Capacitors Thanks to High Switching Frequency
and Fast Feedback Loop Compensation
Start-Up and Soft-Start Function
The DC1859 features internal 10ms soft-start circuit that
prevents input current surge at start-up. The soft-start
circuitalsopreventsoutput voltage overshoot when output
voltage ramp reaches regulation.
IOUT (mA)
EFFICIENCY (%)
95
90
80
70
85
75
65
60
dc1859a F03
1 1000
10000
10010
PWM MODE
Burst Mode OPERATION
VIN = 2.6V
VIN = 5V

4
dc1859afa
DEMO MANUAL DC1859A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
2 1 C2 CAP, 0805 10µF 10% 10V X5R MURATA GRM21BR61A106KE19L
3 1 C3 CAP, 0603 4.7µF 10% 10V X5R AVX 0603ZD475KAT2A
4 1 C4 CAP, 0603 0.1µF 10% 25V X7R AVX 06033C104KAT2A
5 2 C5, C6 CAP, 1206 22µF 20% 25V X5R MURATA GRM31CR61E226ME15L
7 1 C8 CAP, 0805 1µF 20% 16V X5R AVX 0805YD105MAT2A
8 1 C9 CAP, 0603 680pF 10% 25V X7R AVX 06033C681KAT2A
9 1 C10 CAP, 0603 56pF 5% 50V C0G AVX 06035A560JAT2A
12 2 L1, L2 IND, 4.7µH COILCRAFT XAL6060-472MEC
14 1 R1 RES, 0603 28k 1% 1/10W VISHAY CRCW060328K0FKEA
16 1 R4 RES, 0603 1M 1% 1/10W VISHAY CRCW06031M00FKEA
17 1 R5 RES. 0603 110k 1% 1/10W VISHAY CRCW0603110KFKEA
18 1 R6 RES, 0603 51.1k 1% 1/10W VISHAY CRCW060351K1FKEA
19 2 R8, R9 RES, 0603 1M 5% 1/10W VISHAY CRCW06031M00JNEA
20 1 U1 IC, DC/DC CONVERTER LINEAR TECH. LTC3124EDHC#PBF
Additional Demo Board Circuit Components
1 0 C1, C11 CAP. 7343 OPTION OPTION
6 0 C7 CAP, 0603 OPTION OPTION
15 0 R3, R7 RES, 0603 OPTION OPTION
Hardware: For Demo Board Only
10 6 E1, E2, E3, E4, E5, E6 TURRET MILL MAX 2501-2-00-80-00-00-07-0
11 2 JP1, JP2 HEADER, 3 PIN SINGLE ROW SULLINS, NRPN031PAEN-RC
13 4 MH1, MH2, MH3, MH4 STANDOFF, SNAP ON KEYSTONE_8831
21 2 JP1, JP2 SHUNT SAMTEC 2SN-BK-G
QUICK START PROCEDURE
Output Short Circuit Protection
The LTC3124 features safe short-circuit and thermal
protection. The part can operate continuously with output
shortedwhile maintaining amaximum set current limit. The
peak switch current is reduced during overload to about
2A and is restored to 3.5A once the output exceeds 1.5V.
Figure 5. The DC1859 Ramps the Output Slowly at Start-Up
without Generating an Input Current Surge

5
dc1859afa
DEMO MANUAL DC1859A
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM
5 5
4 4
3 3
2 2
1 1
D D C C B B A A
1.5A [1]
NOTE: UNLESS OTHERWISE SPECIFIED,
[1] OUTPUT WITH 5V INPUT. SEE QSG FOR OTHER INPUTS.
VIN
VIN
VOUT
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone]
Milpitas, CA 95035 Phone: [phone]
1630 McCarthy Blvd.
LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
DEMO CIRCUIT 1859A
Wednesday, June 25, 2014
11
DUAL PHASE SYNCHRONOUS STEP-UP
N/A
LTC3124EDHC
MI
GORAN P.
DC/DC CONVERTER
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone]
Milpitas, CA 95035 Phone: [phone]
1630 McCarthy Blvd.
LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
DEMO CIRCUIT 1859A
Wednesday, June 25, 2014
11
DUAL PHASE SYNCHRONOUS STEP-UP
N/A
LTC3124EDHC
MI
GORAN P.
DC/DC CONVERTER
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY
Fax: [phone]
Milpitas, CA 95035 Phone: [phone]
1630 McCarthy Blvd.
LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
DEMO CIRCUIT 1859A
Wednesday, June 25, 2014
11
DUAL PHASE SYNCHRONOUS STEP-UP
N/A
LTC3124EDHC
MI
GORAN P.
DC/DC CONVERTER
E2
GND
E2
GND
JP1
PWM
BURST
MODE
JP1
PWM
BURST
MODE1
3 2
R9
1M
R9
1M
C4
0.1uF
C4
0.1uF
+
C1
(OPT)
+
C1
(OPT) E5
GND
E5
GND
R4 1M 1% R4 1M 1%
R8
1M
R8
1M
R3
OPT
R3
OPT
R6
51.1k
1%
R6
51.1k
1%
C8 1uF
25V
C8 1uF
25V
E1
VIN
1.8V - 5.5V
E1
VIN
1.8V - 5.5V
R5
110k 1%
R5
110k 1%
E3
PWM/SYNC
E3
PWM/SYNC
U1
LTC3124EDHC
U1
LTC3124EDHC
PGNDA
4
VC
9
VIN
5
RT
8
FB
10
SGND
12
SD
11
PGNDB
2
PWM/SYNC
6
SWA
3
VCC
7
SWB
1
VOUTA
13
NC
14
VOUTB
15
CAP
16
EXPOSED PAD
17
+
C11
OPT
+
C11
OPT
C9
680pF
C9
680pF
E4
VOUT
12V
E4
VOUT
12V
L2
4.7uH
XAL6060-472
Coilcraft
L2
4.7uH
XAL6060-472
Coilcraft
R1
28k 1%
R1
28k 1%
L1
4.7uH
XAL6060-472
Coilcraft
L1
4.7uH
XAL6060-472
Coilcraft
E6
SD
E6
SD
C3 4.7uF
10V
C3 4.7uF
10V
JP2
ON
OFF
RUN
JP2
ON
OFF
RUN
1 3 2
C7
OPT
C7
OPT
C10 56pF C10 56pF
C2
10uF
10V
C2
10uF
10V
C5 22uF 25V C5 22uF 25V
C6
22uF 25V
C6
22uF 25V
R7
OPT
R7
OPT

6
dc1859afa
DEMO MANUAL DC1859A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2014
LT 1014 REV A • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LT C ) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LT C for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LT C from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LT C assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LT C currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LT C applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation