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dc1980af
DEMO MANUAL DC1980A
Description
LT3514
Triple Step-Down Switching Regulator
with 100% Duty Cycle Operation
Demonstration circuit 1980A is a triple current mode PWM
step-down DC/DC converter featuring the LT
®
3514. The
demo circuit is designed for 5V, 3.3V and 1.8V outputs
from a 5.4V to 36V input. The current capability of 5V
and 1.8V outputs is 1A and the 3.3V output is capable of
2A output. Individual soft-start and current limit for each
output as well as frequency synchronous function simplify
the complex design of triple-output power converters.
Each converter is synchronized to either a common ex
-
ternal clock input or a resistor programmable 250kHz to
2.2MHz internal oscillator. Programmable frequency allows
optimization between efficiency and external component
size. Each output can be independently disabled using its
own RUN/SS pin.
The LT3514 data sheet gives complete description of the
device, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for the demo circuit 1980A.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, 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
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Input Supply Range 5.4 36 V
V
OUT1
Output Voltage 1 4.85 5 5.15 V
V
OUT3
Output Voltage 3 3.2 3.3 3.4 V
V
OUT4
Output Voltage 4 1.746 1.8 1.854 V
Frequency Switching Frequency V
IN
= 12V 0.9 1 1.1 MHz
I
OUT1
V
OUT1
Maximum Output Current V
IN
= 5.4V ~ 36V 1 A
Specifications are at T
A
= 25°C
Figure 2. Thermal Image at V
IN
= 12V, f = 1MHz with
I
OUT1
= I
OUT4
= 1A and I
OUT3
= 2A
Figure 1. System Efficiency at f = 1MHz with I
OUT1
= I
OUT4
= 1A
and I
OUT3
= 2A
V
IN
(V)
5 15 2510 20 35
30 40
EFFICIENCY (%)
95
100
90
85
80
75
70
60
65
DC1980a F02
