DEMO MANUAL DC1883A
LTC3103EDD
1.8µA Quiescent Current, 15V,
300mA Synchronous Step-Down
DC/DC Converter
Description
Demonstration Circuit 1883A features the LTC
®
3103, a high
efficiency, monolithic synchronous step-down converter
using a current mode architecture capable of supplying
300mA of output current. The IC operates with a fixed
frequency oscillator at 1.2MHz.
The LTC3103 has two user selectable (JP2) operating
modes: Burst Mode
®
operation and forced continuous
operation (fixed frequency PWM). The IC has internal
compensation and an accurate programmable RUN pin.
The LTC3103 operates with a 2.5V to 15V input voltage
range. The demo board has been designed with a main
output set to 1.8V. Since the LTC3103 is a buck converter,
as V
IN
approaches V
OUT
, the output will start dropping out
of regulation. Consult the data sheet for information on
the minimum V
IN
to V
OUT
differential for regulation. The
regulation range is also a function of the load current.
Typical demo board efficiency is shown in Figures 1 and 2.
The LTC3103 data sheet has detailed information about
the operation, specification 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
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
PARAMETER
Input Voltage Range
V
OUT
I
OUT
(T
A
= 25°C)
TYPICAL VALUE
2.5V to 15V
1.8V
300mA
CONDITIONS
(See Note 1)
(See Note 1)
Note 1.
The demo board can operate with V
IN
less than V
OUT
, however V
OUT
will drop out of regulation. The regulation range is a function of I
OUT
. Please
refer to the data sheet for more information.
dc1883Af
1
DEMO MANUAL DC1883A
Quick start proceDure
Using short twisted-pair leads for any power connections
and with all loads and power supplies off, refer to Figure 3
for the proper measurement and equipment setup. The
battery/power supply (PS1) should not be connected to
the circuit until it is stated in the following procedure.
When measuring the input or output voltage ripple, care
must be taken to avoid a long ground lead on the oscil-
loscope probe. Measure the input or output voltage ripple
by touching the probe tip directly across the V
IN
or V
OUT
and GND terminals (see Figure 4), or by using an oscil-
loscope probe tip jack.
1. Jumper, PS1 and LOAD settings to start:
PS1 = OFF
JP1 (RUN) = OFF
JP2 (MODE) = FIXED FREQUENCY
2. With power off, connect the power supply (PS1) as
shown in Figure 3. If accurate current measurements
are desired (for efficiency calculation for example),
then connect an ammeter in series with the supply as
shown. The ammeter is not required, however.
3. Connect a load to V
OUT
, as shown in Figure 3. The load
can be up to 300mA or 6Ω for V
OUT
= 1.8V. Connect an
ammeter if accurate current measurement or monitoring
is desired.
4. Turn on PS1 and slowly increase voltage until the volt-
age at V
IN
is 5V. Move Jumper JP1 to ON.
5. Verify V
OUT
is ~1.8V.
6. V
IN
can now be varied between 3V and 15V. V
OUT
should
remain in regulation.
7. V
IN
can also be varied down to 2.5V. For V
IN
≤ 3V,
V
OUT
may drop out of regulation, as previously de-
scribed.
8. I
OUT
can also be varied from 0mA to 300mA.
9. For Burst Mode operation, move jumper JP2 to BURST.
See the data sheet for more information.
NOTES:
(1) If V
OUT
drops out of regulation, check to be sure
the maximum load has not been exceeded, or that V
IN
is
not below the minimum value for regulation (see
the data sheet).
(2) To measure no-load input current, remove R4.
100
95
90
EFFICIENCY (%)
EFFICIENCY (%)
85
80
75
70
65
60
55
50
3
5
7
11
9
V
IN
(V)
13
15
dc1883a F01
100
100mA LOAD
300mA LOAD
95
90
85
80
75
70
65
60
55
50
3
5
7
11
9
V
IN
(V)
13
15
dc1883a F02
10mA LOAD
1mA LOAD
5mA LOAD
Figure 1. DC1883A Efficiency in PWM Mode
Figure 2. DC1883A Efficiency in Burst Mode Operation
dc1883Af
2
DEMO MANUAL DC1883A
Quick start proceDure
Figure 3. Proper Measurement Equipment Setup
Figure 4. Measuring Input or Output Ripple
VIN
GND
dc1883Af
3
DEMO MANUAL DC1883A
parts List
ITEM
1
2
3
4
5
6
7
8
9
10
1
2
3
1
2
3
4
QTY
1
3
1
1
1
1
1
1
4
1
0
0
0
5
2
2
4
REFERENCE
C1
C2, C4, C6
C3
C7
C8
L1
R1
R2
R3, R4, R5, R6
U1
C5 (OPT)
C9 (OPT)
R9
E1, E2, E3, E4, E5
JP1, JP2
XJP1, XJP2
(Stand-Offs)
PART DESCRIPTION
CAP CER, 10µF 25V, X5R, 1210
,
CAP CER, 1µF 25V, X5R, 0603
,
CAP CER, 22µF 10V, X5R, 20%, 1206
,
CAP CER, 12pF 50V, C0G 5%, 0603
,
CAP CER, 0.1µF 50V, X7R, 0603
,
Inductor, 15µH
RES, 2MΩ, 1/10W, 1%, 0402, SMD
RES, 2.21kΩ, 1/10W, 1%, 0402, SMD
RES, 1MΩ, 1/10W, 1%, 0402, SMD
LTC3103EDD
CAP CER, 1000pF 50V, X7R, 20%, 0603
,
OPT CAP TANT, 68µF 20V, 10%, SMD, 7343
,
OPT RES, 1/10W, 1%, 0402, SMD
Testpoint, Turret 0.094"
JMP 0.079” Single Row Header, 30-Pin
,
Shunt, 0.079" Center
Stand-Off, Nylon, 0.375" Tall
MANUFACTURER/PART NUMBER
TDK, C3225X5R1E106M
TDK, C1608X5R1E105M
TDK, C3216X5R1A226M
TDK, C1608C0G1H120J
TDK, C1608X7R1H104M
Coilcraft, LPS4018-153MLB
Panasonic, ERJ-2GEJ205X
Panasonic, ERJ-2RKF2211X
Panasonic, ERJ2RKF1004X
Linear Technology Corporation, LTC3103EDD
OPT
OPT
OPT
Mill-Max, 2501-2-00-80-00-00-07-0
Samtec, TMM-103-02-L-S
Samtec, 2SN-BK-G
Keystone, 8832 (Snap on)
Required Circuit Components
Additional Demo Board Circuit Components
Hardware—for Demo Board Only
dc1883Af
4
DEMO MANUAL DC1883A
schematic Diagram
dc1883Af
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.
Figure 5. Circuit Schematic
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