DC501A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 501
Universal High Input Voltage 12V/6A POWER SUPPLY
LTC3703
DESCRIPTION
Demonstration circuit 501 is high power, high voltage,
and high efficiency DC/DC buck converter featuring the
LTC3703.
Configuration jumpers allow Burst or Continuous Switch
mode operation (JP1), to turn the power supply On and
OFF (JP2) and Vcc or Boost Bias Supply select (JP3).
This is a general-purpose high voltage DC to DC with an
input voltage range of 20V to 72V. The board is optimized for positive 48V input operation with high voltage
surges up to 72VDC allowed. The limiting factor is the
LTC3703 GN16 package that will not meet
UL/CSA/IEC60950 clearance and creepage distance requirements above the SELV 60VDC maximum due to pin
spacing. If the user wishes to support higher continuous input voltages or compliance to 60950, the LTC3703
is offered in a G-28 pin package. See Data Sheet. However, for the purposes of evaluation, the board will work
reliably up to 72V.
The board has been layed out to support up to 12A of
DC current buy doubling the MOSFETs and input capacitors along with an inductor with lower DC resistance and
higher current ratings. Some forced air cooling will be
required.
The maximum continuous current in free air is 4A. 6A is
permissible with some forced air cooling. The output
voltage is programmed with a voltage divider and configured for 12V.
The demonstration circuit comes with jumpers preset to
power up in the continuous switching mode. Test points
are provided to monitor or control Mode/SYNC, BGRTN
and VCC.
Special consideration must be given to the inductor chosen. The short circuit current has a very wide tolerance
with initial transient spikes that work against the use of a
Ferrite based inductor. A powder based magnetic core
material is highly recommended. Whatever inductor is
chosen, the circuit should be checked for proper short
circuit operation by verifying the inductor does not saturate.
The board can also support a boost converter configuration. See schematic.
Design files for this circuit board are available. Call
the LTC factory.
Table 1. Performance Summary
PARAMETER
CONDITION/NOTES
VALUE
Maximum Input Voltage
Limited by MOSFET Voltage Ratings.
72V ±10 %
Minimum Input Voltage
Efficiency
20V ±10 %
Vin = 48V with 4 amp load
93%
Vin = 24V with 4 amp load
95%
Switching Frequency
User adjustable.
260KHz Nominal
Output Voltage
0 to 6 Amps measured at VOUT and GND terminals.
12V ±2 %
Maximum Current Free Air
Limited by temperature rise of inductor.
4A
Maximum Current with Force Air cooling Accuracy and limit set by Rds-on value of bottom MOSFET. See Datasheet. 6A –0A / +3A
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 501
Universal High Input Voltage 12V/6A POWER SUPPLY
QUICK START PROCEDURE
Demonstration circuit 501 is easy to set up to evaluate
the performance of the LTC3703. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
1.
Connect a power source to the VIN and GND. The
power supply must be capable of at least 120 watts of
power at the input voltage you choose provided it is
within the Vin range permitted.
2.
Connect a load to the VOUT and GND terminals and
set it to 0Amps
3.
Turn on the input power supply and DC501 should
power up.
4.
Adjust load as required for evaluation.
Figure 1. Proper Measurement Equipment Setup
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 501
Universal High Input Voltage 12V/6A POWER SUPPLY
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