LT3757
DEMO CIRCUIT 1341A
QUICK START GUIDE
LT3757EDD
HIGH EFFICIENCY SEPIC CONVERTER
DESCRIPTION
Demonstration circuit 1341A features LT3757EDD in a
300kHz SEPIC converter circuit, designed for 5V out-
put from a 4.5V to 36V input.
The LT3757EDD operates over an input range of 2.9V
to 40V, suitable for applications from single-cell lith-
ium-ion battery portable electronics up to high voltage
automotive and industrial power supplies. It also ex-
hibits low shutdown quiescent current of 1µA, making
them an ideal fit for battery-operated systems. The IC
integrates a high voltage, low dropout linear (LDO)
regulator. Thanks to a novel FBX pin architecture, the
LT3757EDD can be connected directly to a divider
from either the positive output or the negative output
to ground. They also pack many popular features such
as soft-start, input undervoltage lockout, adjustable
frequency and synchronization in a small 10-lead
MSOP package or a 3mm × 3mm QFN package.
The LT3757EDD datasheet gives a complete descrip-
tion of the part, operation and application information.
The datasheet must be read in conjunction with this
quick start guide for demo circuit 1341A.
Design files for this circuit board are available. Call
the LTC factory.
, LTC and LT are registered trademarks of Linear
Technology Corporation.
Table 1. Performance Summary for 300kHz SEPIC Regulator ( TA = 25 C )
PARAMETER
CONDITION
Minimum Input Voltage
Maximum Input Voltage
Output Voltage V
OUT
Maximum Output Current
Typical Switching Frequency
o
VALUE
4.5V
36V
5V +/-3%
3A
300kHz
QUICK START PROCEDURE
Demonstration circuit 1341A is easy to set up to
evaluate the performance of the LT3757EDD. Refer
to Figure 1 for proper measurement equipment
setup and follow the procedure below:
measuring the input or output voltage
ripple, care must be taken to avoid a long ground
lead on the oscilloscope probe. Measure the input
or output voltage ripple by touching the probe tip
directly across the Vin or Vout and GND terminals.
See Figure 2 for proper scope probe technique.
1.
2.
NOTE.
When
3.
Turn on the power at the input.
sure that the input voltage does not
exceed the maximum input voltage.
NOTE.
Make
4.
Check for the proper output voltages.
there is no output, temporarily disconnect
the load to make sure that the load is not set too
high.
NOTE.
If
Place JP1 on the RUN position.
With power off, connect the input power supply
to Vin and GND.
Once the proper output voltages are established,
adjust the loads within the operating range and ob-
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
1
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