DC1548A - Demo Manual

DEMO CIRCUIT 1548A
QUICK START GUIDE
LT3757
LT3757EDD
HIGH EFFICIENCY CUK CONVERTER
DESCRIPTION
Demonstration
circuit
1548A
features
LT3757EDD in a 300kHz CUK converter circuit,
designed for -15V output from a 7V to 28V input.
The LT3757EDD operates over an input range
of 2.9V to 40V, suitable for applications from
single-cell lithium-ion battery portable electronics up to high voltage automotive and industrial
power supplies. It also exhibits low shutdown
quiescent current of 1µA, making them an ideal
fit for battery-operated systems. 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.
It also packs many popular features such as
soft-start, input undervoltage lockout, adjustable
frequency and synchronization in a small 10lead MSOP package or a 3mm × 3mm QFN
package.
The LT3757EDD datasheet gives a complete
description of the part, operation and application
information. The datasheet must be read in conjunction with this quick start guide for demo circuit 1548A.
Design files for this circuit board are available. Call the LTC factory.
LT, LTC and are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
o
Table 1. Performance Summary for 300kHz CUK Regulator ( TA = 25 C )
PARAMETER
CONDITION
Minimum Input Voltage
Maximum Input Voltage
Output Voltage VOUT
Maximum Output Current
Typical Switching Frequency
VALUE
7V
28V
-15V +/-3%
1A
300kHz
QUICK START PROCEDURE
Demonstration circuit 1548A 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:
NOTE. When 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. Place
JP1 on the ON position.
2. With
power off, connect the input power
supply to Vin and GND.
3. Turn
on the power at the input.
NOTE. Make
sure that the input voltage does
not exceed the maximum input voltage.
4. Check
for the proper output voltages.
NOTE. If there is no output, temporarily disconnect the load to make sure that the load
is not set too high.
Once the proper output voltages are established, adjust the loads within the operating
1
LT3757
range and observe the output voltage regulation, ripple voltage, efficiency and other pa-
rameters.
Iout - A + Load+
Vout -
V
+
Iin
- A +
+
V Vin
-
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
2
+
Supply
Power
-
LT3757
3
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