DEMO MANUAL DC1725A
LT3759
Wide Input Voltage Range
Boost/SEPIC/Inverting Controller
DESCRIPTION
The LT3759 is a current mode DC/DC controller operating
over an input range of 1.6V to 42V, making it well suited
for applications ranging from single-cell lithium-ion bat-
tery portable electronics to high voltage automotive and
industrial power supplies. It also exhibits low shutdown
quiescent current of 1μA, making it an ideal fit for battery
operated systems. Thanks to a novel FBX pin architecture,
the LT3759 can be connected directly to a divider from
either a positive or negative output feedback voltage to
ground. It also packs many popular features such as soft-
start, input undervoltage lockout, adjustable frequency and
synchronization in a small 12-lead exposed pad MSOP
package.
Demonstration circuit 1725A features LT3759 in a 485kHz
boost converter, designed for a 5V/2A output from a 1.8V
to 4.5V input. The demo circuit configures the shutdown
voltage at typical 1.70V, which means that the input volt-
age can be dropped to as low as 1.70V, once it starts up.
The start-up voltage is set at 2.5V but can be adjusted by
changing R1 and R2 values.
The LT3759 data sheet gives a complete description of the
part, operation and application information. The data sheet
must be read in conjunction with this quick start guide.
Design files for this circuit board are available at
http://www.linear.com/demo
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
PARAMETER
Input Voltage Range, V
IN
Minimum Start-up Voltage
Switching Frequency
Output Voltage, V
OUT
Maximum Continuous Output Current, I
OUT
Output Voltage Ripple
Typical Efficiency
(T
A
= 25°C)
CONDITIONS
I
OUT
= 0mA~2A
I
OUT
= 2A
V
IN
= 1.8V~4.5V
I
OUT
= 0mA~2A
V
IN
= 1.8V~4.5V
V
IN
= 2.5V, I
OUT
= 2A
V
IN
= 4.5V, I
OUT
= 2A
4.85
2.0
60
90
MIN
1.8
485
5.0
5.15
TYP
MAX
4.5
2.5
UNITS
V
V
kHz
V
A
mV
%
dc1725af
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DEMO MANUAL DC1725A
QUICK START PROCEDURE
Demo circuit 1725A is easy to set up to evaluate the per-
formance of LT3759. Refer to Figure 1 for proper measure-
ment equipment setup and follow the procedure below.
1. With power off, connect the input power supply, load
and meters as shown in Figure 1. Preset the load to 0A,
and V
IN
supply to be 0V. Place jumpers in the following
positions for a typical 5V application:
EN (JP1)
ON
SYNC (JP2)
OFF
NOTE: Make sure that the input voltage does not exceed
4.5V. If higher operating voltage is required, power
components with higher voltage ratings should be used.
3. Once the proper output voltage is established, adjust
the input voltage and load within the operating range
and observe the output voltage regulation, ripple volt-
age, efficiency and other parameters. Typical efficiency
curve is shown in Figure 3.
NOTE: When measuring the input or output voltage
ripples, care must be taken to avoid a long ground
lead on the oscilloscope probe. Measure the input or
output voltage ripple by touching the probe tip directly
across the V
IN
and GND, or V
OUT
and GND terminals.
See Figure 2 for proper scope probe technique.
2. Turn on V
IN
and increase slowly to 2.5V. Check for proper
output voltages. The output should be regulated at 5V
(±3%). The switching frequency should be about 485kHz.
NOTE: If there is no output, or the output is out of spec,
temporarily disconnect the load to make sure that the
load is not set too high, and the power supply current
capability is above 7A. Minimize voltage drop over the
input wires.
dc1725af
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DEMO MANUAL DC1725A
QUICK START PROCEDURE
dc1725a F01
Figure 1. Proper Measurement Equipment Setup
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
INPUT OR OUTPUT CAPACITOR
dc1725a F01
V
IN
= 1.8V
V
IN
= 2.5V
V
IN
= 4.5V
200
400
600
800
1200
1600
2000
1000
1400
1800
LOAD CURRENT (mA)
dc1725a F03
Figure 2. Proper Scope Probe Placement for
Measuring Input or Output Ripple
Figure 3. Efficiency with Different Input Voltages
dc1725af
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DEMO MANUAL DC1725A
PARTS LIST
ITEM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
QTY
4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
7
2
2
2
4
1
1
REFERENCE
CO1, CIN1, CO2, CIN2
CIN3
C1
C2
C3
C4
D1
L1
Q1
RCS1
RFBA
RFBB
R1
R2
R3
R4
R5
U1
E1-E7
JP1, JP2
J1, J2
JP1, JP2
MH1, MH2, MH3, MH4
PART DESCRIPTION
CAP 1210, 100μF 20%, 6.3V, X5R
,
,
CAP 270μF 20%, 10V
,
,
CAP 1206, 4.7μF 10%, 50V, X5R
,
,
CAP 0402, 0.1μF 10%, 16V, X5R
,
,
CAP 0402, 22nF 10%, 25V, X7R
,
,
CAP 0402, 120pF 10% 25V, X7R
,
,
DIODE, SCHOTTKY BARRIER RECTIFIER SMA
IND, 2.2μH
XSTR, N-CHANNEL MOSFET
RES, 0815 0.005Ω, 1% 1W
RES, 0402, 34kΩ, 1%, 1/16W
RES, 0402, 15.8kΩ, 1%, 1/16W
RES, 0402, 348kΩ, 1%, 1/16W
RES, 0402, 887kΩ, 1%, 1/16W
RES, 0402, 5.1kΩ, 1%, 1/16W
RES, 0402, 16.9kΩ, 1%, 1/16W
RES, 0402, 100kΩ, 1%, 1/16W
IC, INVERTING CONVERTER
TURRETS
HEADER, 3-PIN, 2mm
JACK, BANANA
SHUNT, 2mm
STANDOFF, SNAP ON
FAB, PRINTED CIRCUIT BOARD
STENCIL FOR BOTH SIDES
MANUFACTURER/PART NUMBER
MURATA GRM32ER60J107ME20L
SANYO 10SVPC270M
TAIYO YUDEN UMK316BJ475KL
AVX 0402YD104KAT2A
MURATA GRM155R71E223KA61D
AVX 04023C121KAT2A
DIODES INC/ZETEX SBR3U20SA
WÜRTH ELEKTRONIK 7443552200
VISHAY Si7858ADP-T1-E3
SUSUMU/THIN FILM RL3720WT-R005-F
VISHAY CRCW040234K0FKED
VISHAY CRCW040215K8FKED
VISHAY CRCW0402348KFKED
VISHAY CRCW0402887KFKED
VISHAY CRCW04025K10FKED
VISHAY CRCW040216K9FKED
VISHAY CRCW0402100KFKED
LINEAR TECH. LT3759EMSE
MILLMAX 2501-2-00-80-00-00-07-0
SAMTEC TMM-103-02-L-S
KEYSTONE 575-4
SAMTEC 2SN-BK-G
KEYSTONE 8834
DEMO CIRCUIT 1725A
STENCIL 1725A
Required Circuit Components
Hardware/Components (For Demo Board Only)
dc1725af
4
DEMO MANUAL DC1725A
SCHEMATIC DIAGRAM
dc1725af
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.
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