1
DEMO MANUAL DC143
DEMO MANUAL DC143
LTC1474/LTC1475
10
µ
A I
Q
, High Efficiency,
Step-Down DC/DC
Converter
NO DESIGN SWITCHER
DESCRIPTIO
U
This demonstration circuit is a step-down (buck) regulator
using the LTC
®
1474/LTC1475. The exclusive use of surface
mount components and the LTC1474/LTC1475 in the tiny
MSOP package results in a highly efficient application in a
small board space. This demo board highlights the
capabilities of the LTC1474/LTC1475, which use a current
mode, constant off-time architecture to switch an internal
P-channel power MOSFET. This results in a power supply
that has low ripple and fast transient response. At low
output currents the LTC1474/LTC1475 automatically
switch to Burst Mode
TM
operation to maintain high operating
efficiencies and minimize supply current. At no load,only
10
µ
A (typical) is required to regulate the output. The parts
can be shut down to further reduce the supply current to
6
µ
A (typical). In dropout, the internal P-channel MOSFET
is turned on continuously (100% duty cycle), providing
low dropout operation with V
OUT
≅
V
IN
. An onboard low-
battery detector allows the user to monitor the input
supply through an external resistive divider. This board is
intended for applications such as cellular phones, GSM
systems, 4mA to 20mA current-loop pirate supplies or any
portable battery-powered application. Gerber files for this
circuit board are available. Call the LTC factory.
Demo Board D
DM143 DB D
DM143 DB A
LOAD CURRENT (mA)
EFFICIENCY (%)
100
90
80
70
60
50
0.03
3
30
300
DM143 TPC
0.3
V
IN
= 5V
V
IN
= 10V
V
IN
= 15V
L = 100
µ
H
V
OUT
= 3.3V
R
SENSE
= 0
Ω
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
PERFOR
m
A
N
CE SU ARY
U
W
W
W
SYMBOL
PARAMETER
CONDITIONS
BOARD SUFFIX
VALUE
V
IN
Input Voltage Range
V
OUT
= 3.3V
A, B, D, E
3.3V to 18V
V
OUT
= 5V
C, F
5V to 18V
V
OUT
Output Voltage
LTC1474/LTC1475
A, D
3.3V
±
0.10V
LTC1474-3.3/LTC1475-3.3
B, E
3.3V
±
0.10V
LTC1474-5/LTC1475-5
C, F
5V
±
0.15V
I
OUT
Maximum Output Current
R
SENSE
= 0
Ω
ALL
300mA
R
SENSE
= 0.25
Ω
ALL
150mA
I
Q
Typical Supply Current
V
IN
= 10V, I
LOAD
= 0
A, B, C
10
µ
A
V
IN
= 10V, I
LOAD
= 0
D, E, F
15
µ
A
TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO
U
U
W
Board A, B, D, E Efficiency
Demo Board A
