DC1487A - Demo Manual

DEMO CIRCUIT 1487A
QUICK START GUIDE
LTC3854EMSE
WIDE INPUT RANGE AND SMALL FOOTPRINT
BUCK CONVERTER
DESCRIPTION
Demonstration circuit 1487A is a small foot print,
wide input voltage range, high efficiency synchronous buck converter with 4.5V to 34V input range. It
can supply 12A maximum load current at 2.5V output. The demo board features the LTC®3854EMSE
controller. The controller features a 400kHz constant
frequency current mode architecture. With a wide
input range and output range, the LTC3854 is ideal
for automotive, telecom, industrial and distributed
DC power systems. The demo board uses a high
density, two sided drop-in layout with a minimal
amount of components.
The package of
LTC3854EMSE is a small, low thermal impedance
12-lead plastic MSOP.
Table 1.
The RUN/SS pin (JP1) provides both soft-start and
enable features. To shut down the converter, one
simple way is to force the RUN pin below 0.4V (JP1:
OFF).
Design files for this circuit board are available. Call
the LTC factory.
Performance Summary (TA = 25°C)
PARAMETER
CONDITION
Input Voltage Range
VALUE
4.5V to 34V
Output Voltage, VOUT
VIN = 4.5-34V, IOUT = 0A to 12A
2.5V ±2%
Maximum Output Current, IOUT
VIN = 4.5-34V, VOUT = 2.5V
12A
Typical Efficiency
VIN = 20V, VOUT = 2.5V, IOUT = 12A
92%
Typical Switching Frequency
400kHz
1
LTC3854EMSE
QUICK START PROCEDURE
Demonstration circuit 1487A is easy to set up to
evaluate the performance of the LTC3854EMSE. Refer
to Figure 1 for the proper measurement equipment
setup and follow the procedure below:
1. With power off, connect the input power supply to Vin (4.5V-34V) and GND (input return).
2. Connect the 2.5V output load between Vout
and GND (Initial load: no load).
3. Connect the DVMs to the input and outputs.
4. Turn on the input power supply and check for
the proper output voltages. Vout should be
2.5V+/-2%.
5. Once the proper output voltages are established, adjust the loads within the operating
range and observe the output voltage regulation, ripple voltage and other parameters.
Note: When measuring the output or input voltage
ripple, do not use the long ground lead on the oscilloscope probe. See Figure 2 for the proper scope probe
technique. Short, stiff leads need to be soldered to the
(+) and (-) terminals of an output capacitor. The
probe’s ground ring needs to touch the (-) lead and
the probe tip needs to touch the (+) lead.
2
LTC3854EMSE
Figure 1. Proper Measurement Equipment Setup
+
COUT
VOUT
-
GND
Figure 2. Measuring Output Voltage Ripple
3
LTC3854EMSE
Figure 3. Efficiency vs load current
4
LTC3854EMSE
5
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