DC558A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 558A
3-PHASE HIGH EFFICIENCY DC/DC CONVERTER
LTC3731CUH
DESCRIPTION
Demonstration circuit 558 is a high current step-down
TM
PolyPhase converter featuring the LTC3731 threephase synchronous buck controller. The demo circuit
input voltage is from 5V to 14V and output is 1.5V/60A.
To minimize the supply footprint size and improve the
thermal performance, the 5mm x 5mm QFN package
LTC3731CUH controller is used. High density power
components are used and the power components is
2
within a 0.8 x 2.3 inch footprint area.
Design files for this circuit board are available. Call
the LTC factory.
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
5V
Maximum Input Voltage
14V
VOUT
IOUT = 0A to 60A
1.5V±1%
Without heat sink, without cooling fan
50A
Without heat sink, with cooling fan (300LFM)
60A
With heat sink, with cooling fan (300LFM)
70A
Nominal Switching Frequency
Set by resistor divider on demo boards
400kHz
Typical Efficiency
VIN = 12V, VOUT = 1.5V, IOUT = 60A, using external +5V for IC
bias
82.4%
Maximum Continuous Load Current
o
(∆TMAX=50 C)
QUICK START PROCEDURE
Demonstration circuit 558 is easy to set up to evaluate
the performance of the LTC3731CUH. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below:
1.
2.
Preset the following jumpers on the demo board:
FCB-CCM, FREQ-INT PROG, 5V SEL-INT, DLC BIASOFF and DLC-OFF. With above jumpers setup, the
supply is running at about 400kHz phase frequency,
and using the on board +5V bias supply.
Preset the voltage of the input power supply to be
12V. Preset the current limit of input power supply to
be large than 25A. With power off, connect the input
power supply to Vin and GND.
3.
Connect the electronic load to Vout+ and Vout-. Preset the load current to be 0A.
4.
Turn on the power at the input.
5.
Check for the proper output voltages at no load and
full load. Vout = 1.485V to 1.515V. Cooling fan is
needed if the load current is higher than 50A.
6.
Adjust the loads and input voltage within the operating range and observe the output voltage regulation,
efficiency and other parameters.
7.
(Optional) DC558A board has optional +5V bias input
pins for better efficiency at 12V supply input voltage.
To use the external 5V bias voltage, set jumper 5V
SEL-EXT. Apply the supply input voltage before applying the +5V bias voltage.
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 558A
3-PHASE HIGH EFFICIENCY DC/DC CONVERTER
puts to oscilloscope inputs. Adjust R34 and R38 for
desired load current step and rising slope. Adjust R33
for desired load current falling slope.
V
Iout
V
Current Shunt
Load
60A
(Optional) To perform the load transient test, set
jumpers DLC BIAS-ON and DLC-ON. Use coaxial cables to connect LOAD STEP and Vout+ coaxial out-
Vin
Vin
Current Shunt
V
V
Optional
+5V Bias
Supply
Iin
Vout
8.
Figure 1. Proper Measurement Equipment Setup
2
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