Linear Technology 431 User manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 431
ISOLATED TRIPLE OUTPUT TELECOM CONVERTER
1
LT1725, LTC1773, LTC4210
DESCRIPTION
Demonstration circuit 431 is a simple isolated
telecom converter, built in the footprint of a stan-
dard “half-brick”. The input voltage range is 36-
72V and three outputs are provided, 5V 3.3V and
2.5V. Total available power is 30W. Design files
for this circuit board are available. Call the LTC
factory.
Table 1. Performance Summary
PARAMETER CONDITION VALUE
Input Voltage 36-72V
VOUT1 VIN 36-72V, Iout1 = >50mA – 1A 5V +-3%
VOUT2 VIN 36-72V, Iout2 = 0-5A 3.3V +-3%
VOUT3 VIN 36-72V, Iout3 = 0-4A 2.5V +-3%
Isolation 1 min 1500V
Efficiency V
IN
=48V, Iout1 = 1A, Iout2 = 5A, Iout3 =
4A
73% typ.
OPERATING PRINCIPLES
Demo DC431 is a simple isolated triple output
converter that might be used in a small telecom
system. Input power, nominally 48V, is converted
to isolated 5V by an LT1725 based flyback con-
verter. This isolated 5V rail serves as the input for
two LTC1773 based synchronous buck converters
that separately derive the two low voltage rails
from the isolated 5V rail. The benefit of this archi-
tecture is its flexibility, since the low voltage rails
are derived from separate converters their outputs
can be modified to suit the application without
modifying the main power transformer.
QUICK START PROCEDURE
Demonstration circuit 431 is easy to set up. Refer
to Figure 1 for proper measurement equipment
setup and follow the procedure below:
1. With the power off, connect the input power
supply, meters and loads as shown in Figure 1.
2. The demo is now set up for evaluation. Turn on
the input power and adjust the output loads.
3. The board can be shutdown by connecting the
shutdown pin to the VIN- input.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 431
ISOLATED TRIPLE OUTPUT TELECOM CONVERTER
2
Figure 1. Proper Measurement Equipment Setup

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 431
ISOLATED TRIPLE OUTPUT TELECOM CONVERTER
3