1
dc2172af
DEMO MANUAL DC2172A
Description
LTC7138
High Efficiency, High V
IN
,
Step-Down Regulator
Demonstration circuit 2172A is a high input voltage, 400mA
step-down regulator featuring the LTC7138. The output of
the regulator can be programmed for either 5V, 3.3V or
1.8V with on-board jumpers or is adjustable from 800mV
to V
IN
using an optional feedback divider. The input voltage
range is from 4V to 140V. The LTC7138’s Burst Mode
®
operation, low quiescent current and internal top FET
switch provide high efficiency over a wide range of loads.
Other features include:
•
Optional components to adjust the current limit, make it
proportional to V
IN
or improve the efficiency and reduce
the output voltage ripple.
L
, LT, LTC, LTM, Burst Mode, 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
•
FBO turret to tie two or more LTC7138 regulators to-
gether if the application requires more load current.
•
Optional UVLO and OVLO divider.
•
External/internal soft-start.
For more details, refer to the LTC7138 data sheet. The
LTC7138 data sheet gives a complete description of the
IC 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/DC2172A
Specifications are at T
A
= 25°C
PARAMETER
CONDITIONS
VALUE
Input Voltage Range
4V to 140V
5.0V Output Voltage
V
IN
= 12V, I
OUT
= 0mA to 400mA
5.0V ±2%
3.3V Output Voltage
V
IN
= 12V, I
OUT
= 0mA to 400mA
3.3V ±2%
1.8V Output Voltage
V
IN
= 12V, I
OUT
= 0mA to 400mA
1.8V ±2%
Maximum Output Current, I
OUT
V
IN
= 4V to 140V, V
OUT
= 5.0, 3.3V, 1.8V or ADJ (V
OUT
≤ V
IN
)
400mA
Typical Efficiency
V
IN
= 12V, V
OUT
= 5V, I
OUT
= 400mA
82.3%
Typical Output Ripple
V
IN
= 12V, V
OUT
= 5V, I
OUT
= 400mA
87mV
P-P
Downloaded from
