DC1271A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271
HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER
LTC3854EDDB
DESCRIPTION
Demonstration circuit 1271 is a high efficiency,
small footprint, step-down DC-DC converter featuring the LTC3854EDDB. Its output supplies 1.5V
@ 15A and its input voltage range is 4.5V to 14V.
The demo board uses a high density, two sided
drop-in layout with a minimal amount of components. The power components, excluding the bulk
output capacitors and bulk input capacitors, fit
within a 1.38” X 0.56” area on the top layer. The
control circuit on the bottom layer fits within a
0.44” X 0.50” area.
Table 1.
This demo board provides the user with a simple,
low parts count solution for a high output, low output voltage current buck converter. The LTC3854
operates at a switching frequency of 400kHz and
CCM at light load.
Design files for this circuit board are available.
Call the LTC factory.
Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
4.5V
Maximum Input Voltage
14V
Output Voltage VOUT
VIN = 4.5V to 14V, IOUT = 0A to 15A
Maximum Output Current
1.5V ±2%
15A
Typical Output Ripple VOUT
VIN = 12V, IOUT = 15A (20MHz BW)
Nominal Switching Frequency
15mVP–P
400kHz
Efficiency (see Figure 3 for efficiency curves)
VIN = 12V, IOUT = 15A
86.9% typical
QUICK START PROCEDURE
Demonstration circuit 1271 is easy to set up to
evaluate the performance of the LTC3854EDDB.
Refer to Figure 1 for proper measurement equipment setup and follow the procedure below:
1) Place RUN pin jumper in the ON position.
2) With power off, connect the input power supply
between VIN and GND.
3) Turn on the power at the input.
4) Check for the proper
VOUT = 1.47V to 1.53V
output
voltages.
5) Once the proper output voltages are established, adjust the loads within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
NOTE: When
measuring the output voltage ripple,
care must be taken to avoid a long ground lead on
the oscilloscope probe. See Figure 2 for proper
scope probe technique. Short, stiff leads should
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.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271
HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER
A
A
Iin
Vin
V
Vin
supply
Iout
Load
V
Vout
Figure 1. Proper Measurement Equipment Setup
+
COUT
VOUT
-
GND
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271
HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER
1.5V/15A LTC3854EDDB converter
95%
Efficiency
90%
85%
Qtop = RJK0305DPB
Qbottom = RJK0330DPB
L = Toko FDA1055-R56M
Rsense = 2mOhms
Fsw = 400kHz
Mode = CCM
Design optimized for a 12V input
80%
75%
70%
0
2
4
6
8
10
12
14
16
Load current (Amps)
Vin = 12V
Vin = 5V
Figure 3. Typical Efficiency Curves
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271
HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER
4
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