1
DEMO MANUAL DC290
NO-DESIGN SWITCHER
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS A
N
D BOARD PHOTO
U
W
U
PERFOR
m
A
N
CE SU
ARY
U
W
W
W
DESCRIPTIO
U
LTC1877/LTC1878
Monolithic Synchronous
Step-Down Regulator
SYMBOL PARAMETER
CONDITIONS
JUMPER POSITION
VALUE
V
IN
Input Voltage Range
LTC1877
All (Note 1)
2.65V to 10V
LTC1878
All
2.65V to 6V
V
OUT
Output Voltage
V
IN
= 5V, SYNC/MODE = 0V, RUN = 5V, I
OUT
= 0mA JP1 = U, JP2 = L, JP3 = “1.5V”
1.51V
±
0.05V
V
IN
= 5V, SYNC/MODE = 0V, RUN = 5V, I
OUT
= 0mA JP1 = U, JP2 = L, JP3 = “2.5V”
2.52V
±
0.08V
V
IN
= 5V, SYNC/MODE = 0V, RUN = 5V, I
OUT
= 0mA JP1 = U, JP2 = L, JP3 = “3.3V”
3.33V
±
0.10V
V
IN
= 5V, SYNC/MODE = 0V, RUN = 5V, I
OUT
= 0mA JP1 = U, JP2 = L, JP3 = “OPEN”
(Note 2)
Demonstration circuit DC290 is a constant-frequency
step-down converter using an LTC
®
1877 or an LTC1878
monolithic synchronous regulator. The LTC1878 has an
input voltage range of 2.65V < V
IN
< 6V and the LTC1877
has an input voltage range of 2.65V < V
IN
< 10V. The
LTC1878 is optimized for low voltage operation and is
ideally suited for single Li-Ion cell or 3-NiCd/NiMH cell
applications. The LTC1877, with its higher voltage capa-
bility, is ideally suited for two Li-Ion cells or 4- to 6-NiCd/
NiMH cell applications.
The exclusive use of low profile surface mount compo-
nents on this demo board results in a highly efficient
application in a small volume. The output voltage can be
selected from 1.5V, 2.5V, 3.3V or a user programmable
voltage, by means of a jumper. The frequency is internally
set at 550kHz or can be synchronized with an external
clock. The internal switches allow up to 600mA of output
current in an MSO8 package, providing a space-efficient
solution for battery-powered applications. The DC supply
current is typically only 10
µ
A at no load and less than 1
µ
A
in shutdown. In switching-noise sensitive applications,
Burst Mode
TM
operation can be inhibited by grounding the
SYNC/MODE pin with a jumper or synchronizing it with an
external clock. Gerber files for this circuit board are
available. Call the LTC factory.
DEMO BOARD
EFFICIENCY CURVE
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
OUTPUT CURRENT (mA)
0.1
EFFICIENCY (%)
10
1000
100
95
90
85
80
75
70
65
60
55
50
290A • TA01
1.0
100
V
IN
= 3.6V
V
IN
= 10V
V
OUT
= 3.3V
L = 10
µ
H
Burst Mode OPERATION
V
IN
= 7.2V
V
IN
= 5V
