DC1316A - Demo Manual

DEMO CIRCUIT 1316
QUICK START LT1913
GUIDE
LT1913EMSE
3.5A,25V Step-down Switching Regulator with SYNC Function
DESCRIPTION
Demonstration circuit 1316 is a monolithic stepdown DC/DC switching regulator featuring LT1913.
The LT1913 can be synchronized over a 250 KHz
to 2 MHz range. The demo board is designed for
5V output from a 6.5V to 25V input. The wide input
range of the LT1913 allows a variety of input
sources. The typical sources are automotive batteries, wall adaptors and industrial supplies.
RUN/SS pin can be used to set the part in micropower shutdown mode, reducing the supply current to less than 1uA. The RUN/SS pin can also be
used to program soft start. In this mode, the
RUN/SS pin is driven through an external RC filter
to create a voltage ramp on this pin. The soft start
function reduces the input current surge during
start-up.
An optional EMC filter at the input is provided on
the bottom of the board, which greatly reduces the
conductive EMI noise at the input side. Customers
can use this optional circuit by cutting the input
trace on the bottom of the board and install the
components. The current mode control scheme
creates fast transient response and good loop stability. The gate drive of the internal switch is
boosted to a voltage that is higher than the Vin to
ensure saturation of the switch. The LT1913’s integrated boost diode reduces the parts count. The
The LT1913 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 1316.
Note: It is best to ground the SYNC pin if the
SYNC function is not being used.
Design files for this circuit board are available.
Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
Performance Summary for Step-down Switching Regulator ( TA = 25oC )
PARAMETER FOR BUCK REGULATOR
Minimum Input Voltage
Maximum Input Voltage
Output Voltage VOUT
Maximum Output Current
Typical Switching Frequency
CONDITION
VALUE
6.5V
25V
5V +/- 4%
3.5A
800kHz
QUICK START PROCEDURE
Demonstration circuit 1316 is easy to set up to
evaluate the performance of the LT1913. 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
LT1913
2. With power off, connect the input power supply
to Vin and GND.
3. Turn on the power at the input.
4. Check for the proper output voltage.
NOTE. If there is no output, temporarily disconnect the load to
make sure that the load is not set too high.
5. Once the proper output voltage is established,
adjust the load within the operating range and
observe the output voltage regulation, ripple
voltage, efficiency and other parameters.
6. An external clock can be added to the SYNC pin
when SYNC function is used. See synchronization section in the datasheet for details.
+
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A
+
+
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+
V
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+
V
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Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
2
A
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Load
1. Place JP1 on the RUN position.
LT1913
Trace cut
Figure 3. The Bottom of the demo Board with the Optional Circuit and the Input Trace Cut
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LT1913
4
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