DEMO CIRCUIT 1450A
QUICK START GUIDE
SMALL FOOTPRINT BUCK CONVERTER
Demonstration circuit 1450A is a small foot print, The RUN/SS pin (JP1) provides both soft-start and
high efficiency synchronous buck converter with enable features. To shut down the converter, one
4.5V to 26V input range. It can supply 5A maximum simple way is to force the RUN pin below 0.4V (JP1:
load current at 2.5V output. The demo board features OFF).
the LTC®3854EDDB controller. The controller fea-
tures a 400kHz constant frequency current mode Design files for this circuit board are available. Call
architecture. With a wide input range and output the LTC factory.
range, the LTC3854 is ideal for automotive, telecom,
industrial and distributed DC power systems. This
board has a compact solution size with dual So-8
MOSFETs, small inductor and capacitor footprints.
The package of LTC3854EDDB is a small, low ther-
mal impedance, 12-Lead (3mm x 2mm) plastic DFN.
Table 1. Performance Summary (TA = 25°C)
PARAMETER CONDITION VALUE
Input Voltage Range 4.5V to 26V
Output Voltage, VOUT VIN = 4.5-26V, IOUT = 0A to 5A 2.5V ±2%
Maximum Output Current, IOUT VIN = 4.5-26V, VOUT = 2.5V 5A
Typical Efficiency VIN = 15V, VOUT = 2.5V, IOUT = 5A 89.5%
Typical Switching Frequency 400kHz
QUICK START PROCEDURE
Demonstration circuit 1450A is easy to set up to
evaluate the performance of the LTC3854EDDB. Refer
to Figure 1 for the proper measurement equipment
setup and follow the procedure below:
1. With power off, connect the input power sup-
ply to Vin (4.5V-26V) 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
5. Once the proper output voltages are estab-
lished, adjust the loads within the operating
range and observe the output voltage regula-
tion, ripple voltage and other parameters.
Note: When measuring the output or input voltage
ripple, do not use the long ground lead on the oscillo-
scope 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.
Figure 1. Proper Measurement Equipment Setup
+ COUT -
Figure 2. Measuring Output Voltage Ripple
Figure 3. Efficiency vs load current
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