Linear Technology LTC3118EUFD Quick setup guide

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DEMO MANUAL DC2045A
Description
LTC3118EUFD
18V, 2A Buck-Boost DC/DC Converter
with Low-Loss Dual Power Path
Demonstration Circuit 2045A featuring the LTC3118 is a
dual input fixed frequency synchronous buck-boost con-
verterwithanintelligentintegratedlow-lossPower-Path™.
The unique all N-Channel architecture provides efficient
operation from either input source to a programmable
output voltage above, below or equal to the input. Volt-
age capability of up to 18V provides flexibility and voltage
margin for a variety of applications and power sources.
The LTC3118 uses a low noise, current mode architecture
with a fixed 1.2MHz PWM mode frequency that minimizes
the solution footprint. For high efficiency at light loads,
automatic Burst Mode™ operation can be selected con-
suming only 50μA of quiescent current in sleep.
TypicalefficienciesforbothBurstModeandfixedfrequency
are shown in Figure 1. JP2 in the FIXED FREQ position
results in low output ripple but also lower efficiency at
light loads. Moving the JP2 position to AUTOBURST
enables Burst Mode operation which improves efficiency
at light load.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
performance summary
System level features include selectable IDEAL DIODE
Mode (shown in Figure 2) or PRIORITY mode operation
(shown in Figure 3)
The system can be monitored through V1GD, V2GD and
PGD (power good) indicators There are accurate RUN
comparators to program independent UVLO thresholds,
and outputdisconnect in shutdown. Other features include
2μA shutdown current, short-circuit protection, soft-start,
inductor current limit and thermal overload protection.
The DC2045A circuit has excellent transient load response
in both fixed frequency and automatic Burst Mode opera-
tion as shown in Figures 4 and 5.
The LTC3118 data sheet has detailed information about
the operation, specifications, and applications of the part.
The data sheet should be read in conjunction with this
Quick Start Guide.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2045A
Specifications are at TA= 25°C
Input Voltage Range: 2.5V to 18.0V
VOUT 5.0V
IOUT 2.0A for VIN > 5.0V

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DEMO MANUAL DC2045A
Quick start proceDure
0
10
20
30
40
50
60
70
80
90
100
1 10 100 1000 10000
EFFICIENCY (%)
LOAD (mA)
VIN=3.3V, BURST MODE
VIN=5V, BURST MODE
VIN=12V, BURST MODE
VIN=3.3V, FIXED FREQ
VIN=5V, FIXED FREQ
VIN=12V, FIXED FREQ
Figure 1. Typical Efficiency as a Function of Input Voltage and Load Current
Figure 3. Transitioning from VIN1 to VIN2 and Back in PRIORITY Mode Operation with VIN2 at 14V
Figure 2. Ideal Diode Mode Operation
VOUT = 100mV/DIV
VOUT DC = 5V
VIN2 = 2V/DIV
VIN2 DC = 8V
VIN1 = 2V/DIV
VIN1 PEAK = 10V
VIN1 VALLEY = 4V
VOUT = 500mV/DIV
VOUT DC = 5V
IIN1 = 500mA/DIV
VIN2 = 14V and is Not Shown on Screen
VIN1 = 2V/DIV
VOLTAGE PEAK = 10V
VOLTAGE VALLEY = 1V

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DEMO MANUAL DC2045A
Quick start proceDure
Figure 4. 100mA to 600mA Load Transient with VIN1 = 3.5V in Fixed Frequency Mode
OUTPUT VOLTAGE
OUTPUT CURRENT
Figure 5. 50mA to 600mA Load Transient with VIN1 = 3.5V in Burst Mode
OUTPUT VOLTAGE
OUTPUT CURRENT

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DEMO MANUAL DC2045A
Quick start proceDure
Using short twisted pair leads for any power connections
and with all loads and power supplies off, refer to Figure 6
for the proper measurement and equipment setup. The
Power Supplies should not be connected to the circuit
until told to do so in the procedure below.
When measuring the input or output voltage ripple, care
must be taken to avoid a long ground lead on the oscil-
loscope probe.
The indicators for PGD, V1GD and V2GD are negative
logic. PGD indicates the output voltage is good if it is
pulled to ground and V1GD and V2GD indicate that the
input voltage on the respective sources are good if the
pins are pulled to ground.
1. JP1 and JP2 settings to start:
JP1 SELECT = IDEAL DIODE (VCC)
JP2 MODE = FIXED FREQ (VCC)
2. With power OFF connect the power supplies (PS1,
PS2) as shown in Figure 6. If accurate current mea-
surements are desired (for efficiency calculations for
example) then connect the ammeters in series with
the supplies as shown. The ammeters however, are
not required.
3. Connect the load, set at 50Ω, to VOUT as shown in
Figure6.Again, connect an ammeter if accurate current
measurement or monitoring is desired.
4. Turn on the Power Supply, PS1, and slowly increase
the voltage. The converter will start at approximately
2.9V.
5. Verify VOUT is ~5.0V, and that V2GD is pulled high by
VCC and PGD and V1GD are pulled low.
6. PS1 can now be varied between 2.5V and 18.0V. VOUT
will remain in regulation for load currents up to 2 amps
with VIN greater than VOUT. As VIN1 falls below VOUT the
input current may increase to the maximum average
inductor current, depending on the load, which will
then limit the load current and the output voltage.
7. Turn off PS1 and repeat steps 3 to 6 with PS2. The part
will turn on with PS2 at approximately 4.5V. Once on,
PS2 can be varied between 3.8V and 18V. The voltage
measurements of step 5 will change where V1GD will
be at VCC and V2GD will be pulled low. Set the load to
50Ω.
8. Set PS2 to 7V and turn on PS1 slowly increasing the
voltage from 0V to 8V. Note that PS1 starts to supply
the power as the voltage of PS1 exceeds the voltage
on PS2 by at least 400mV.
9. Now decrease the voltage on PS1 and observe that
when the voltage on VIN1 falls below the voltage on
PS2, PS1 stops supplying the power and PS2 takes
over. See Figure 2 for typical performance for steps
8 and 9.
10. Turn off PS1 and PS2. Change the SELECT jumper
(JP1) to VCC (the PRIORITY position). Turn on PS2
and adjust it to 14V.
11. By cycling the voltage on PS1 from 1V to 10V you can
observe the transition of power from PS2 to PS1 and
back as the voltage on VIN1 goes through its startup
(approximately 2.9V) and shutdown (approximately
2.5V)thresholds.Typical response is showninFigure3.
Turn off PS1 and PS2.
Steps 12 and 13 are optional for looking at load step
response if desired.
12. With JP2 in the FIXED FREQ position and PS1 at 3.5V
switch the load from 100mA to 600mA and back. Note
the output voltage response. (Figure 4).
13. With JP2 in AUTOBURST and PS1 at 12V switch the
load from 50 mA to 600 mA and back. Note the output
voltage ripple. (Figure 5). See the data sheet for more
information.
Note: Remove D1 for VOUT > 5V to prevent damage to
the converter.

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DEMO MANUAL DC2045A
Quick start proceDure
PS2
PS1
AM2
AM3
VM2
VM1
VM3
10k
10k
AM1
LOAD
PGD
V2GD
V1GD
Figure 6. Measurement Setup

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DEMO MANUAL DC2045A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C1, C4 CAP., 22µF, X7R, 25V, 20%, 1812 TDK, C4532X7R1E226M250KC
2 3 C2, C5, C9 CAP., 1µF, X7R, 25V, 10%, 0603 TDK, C1608X7R1E105K080AB
3 0 C3, C6 (OPT) CAP., ALUM., RADIAL, 150µF, 50V, 20% PANASONIC, EEU-FM1H151
4 2 C7, C8 CAP., 47µF, X5R, 10V, 20%, 1812 TDK, C4532X5R1A476M280KA
5 1 C10 CAP., 1800pF, C0G, 50V, 5%, 0603 TDK, CGJ3E2C0G1H182J080AA
6 1 C11 CAP., 22PF, NPO, 25V, 10%, 0603 KEMET, C0603C220K3GACTU
7 2 C12, C13 CAP., CER 0.1µF, 25V, 10%, X7R, 0603 TDK, C1608X7R1E104K
8 2 C14, C17 CAP., CER 0.047µF, 50V, 10%, X7R, 0603 TDK, C1608X7R1H473K080AA
9 2 C15, C16 CAP., 0.01µF, X7R, 25V, 10%, 0603 TDK, C1608X7R1E103K080AA
10 1 C18 CAP., 4.7µF, X5R, 6.3V, 20%, 0603 TDK, C1608X5R0J475M080AB
11 0 C19, C20, C21 (OPT) CAP., OPTION, 0603
12 1 D1 DIODE, SCHOTTKY, 30V, 0.2A, SOD-523F FAIRCHILD SEMI., BAT54XV2
13 1 L1 INDUCTOR, PWR., SHIELED, 3.3µH. XAL 40xx Series COILCRAFT, XAL4030-332MEC
14 1 R1 RES., 402k, 1/16W, 1%, 0402 VISHAY, CRCW0402402KFKED
15 1 R2 RES., 100k, 1/16W, 1%, 0402 VISHAY, CRCW0402100KFKED
16 1 R3 RES., 40.2k, 1/16W, 1%, 0402 VISHAY, CRCW040240K2FKED
17 5 R4, R6, R8, R9, R10 RES., 1M, 1/16W, 1%, 0402 VISHAY, CRCW04021M00FKED
18 1 R5 RES., 715k, 1/16W, 1%, 0402 VISHAY, CRCW0402715KFKED
19 1 R7 RES., 374k, 1/16W, 1%, 0402 VISHAY, CRCW0402374KFKED
20 1 R11 RES., 49.9Ω, 1/16W, 1%, 0402 VISHAY, CRCW040249R9FKED
21 0 R12 RES., OPTION, 0402
22 1 U1 I.C.,18V, 2A BUCK-BOOST DC/DC CONVERTER WITH
LOW-LOSS DUAL INPUT POWERPATH
LINEAR TECHNOLOGY, LTC3118EUFD*PBF
23 12 E1-E12 TP, TURRET, 0.094", MTG. HOLE MILL-MAX, 2501-2-00-80-00-00-07-0
24 2 JP1, JP2 CONN., HEADER, 1×3, 2mm SAMTEC, TMM-103-02-L-S
25 2 XJP1-XJP2 SHUNT, 2mm SAMTEC, 2SN-BK-G
26 4 STAND OFF STANDOFF, NYLON, SNAP-ON, 0.625" KEYSTONE, 8834 (SNAP ON)
27 1 PCB, DC2045A DEMO CIRCUIT 2045A-2
28 2 STENCILS, DC2045A (TOP & BOTTOM) STENCILS, DC2045A-2 - TOP & BOTTOM

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DEMO MANUAL DC2045A
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
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DEMO MANUAL DC2045A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2015
LT 0315 • PRINTED IN USA
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