DC1234B - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1234
HIGH POWER, DUAL PHASE SYNCRONOUSE BOOST CONVERTER
LT3782, LTC4440
DESCRIPTION
Demonstration circuit DC1234 is a DC/DC boost converter featuring the LT3782 constant frequency current mode boost controller. The synchronous rectification based on high side driver LTC4440 significantly improves converter efficiency. The DC1234
operates over 10V to 15V input voltage range and
provides 8A of output current at 24V output. The 250
kHz constant frequency operation results in a small
and efficient circuit. The converter provides high output voltage accuracy (typically ±3%) over wide load
range with no minimum load requirement. The demonstration circuit can be easily modified to generate
Table 1.
different output voltages. Please consult LTC factory
for details. The DC1234 has a small circuit footprint.
It is a high performance and cost effective solution
for Telecom, Automotive and Industrial applications.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Performance Summary (TA = 25°C)
PARAMETER
Minimum Input Voltage
CONDITIONS
VALUE
10.0V
Maximum Input Voltage
15.0V
Maximum Output Current
8.0A
Output Voltage
24.0V ±3%
Typical Output Ripple
VIN = 12V, IOUT = 6.0A (20 MHz BW)
<120mVP–P
Efficiency
Vin 10V, Io 8.0A
Vin 12V, Io 8.0A
Vin 15V, Io 8.0A
96%
97%
97%
Switching Frequency
250kHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1234
HIGH POWER, DUAL PHASE SYNCRONOUSE BOOST CONVERTER
QUICK START PROCEDURE
Demonstration circuit DC1234 is easy to set up to
evaluate the performance of the LT3782 in a synchronous rectification application. For proper measurement equipment setup refer to Figure 1 and follow
the procedure below:
NOTE: When measuring the input or output voltage ripple, care must be taken to minimize the
length of the oscilloscope probe ground lead.
Measure the input or output voltage ripple by connecting the probe tip directly across the VIN or
VOUT and GND terminals as shown in Figure 2
1. With power off, connect the input power supply to
VIN and GND. Connect load to VOUT and GND
terminals; make sure that load does not exceed
8.0A.
2. Check the VCC Bias voltage-setting jumper JP1.
Move it to the VIN position.
3. Turn the input power source on and slowly increase the input voltage. Be careful not to exceed
15V.
the output voltage regulation, ripple voltage, efficiency and other parameters
PROGRAMMING OF MAXIMUM DUTY CYCLE
Maximum Duty Cycle can be programmed by the voltage
on DCL pin. In this case the DCL pin voltage can be derived from Rset pin. The Rset pin generates a 2.3V reference voltage that can be divided down to the desired
value by resistors R28 and R32.
Keep in mind that combine value of R28+R32 are used
to set the switching frequency also. In order to keep frequency constant, R28+R32 should stay constant as well.
Please refer to the datasheet for more information.
Warning – This board is not designed to work with
input voltages greater than a maximum of 15V. OVLO
circuit based on transistor Q5 disables converter’s
operation, if input voltage exceeds maximum plus 2530%.
NOTE: Make sure that the input voltage VIN
does not exceed 15V. If higher operating voltage is required, power components with higher
power ratings should be used. Also, Jumper
VCC Bias JP1 will have to be moved to the LR
position. Keep it in VIN position if input voltage
less than 15V. Please consult LTC factory for
details.
4. Check for the proper output voltage of 24V.
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 8A range and observe
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1234
HIGH POWER, DUAL PHASE SYNCRONOUSE BOOST CONVERTER
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1234
HIGH POWER, DUAL PHASE SYNCRONOUSE BOOST CONVERTER
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