DC1286A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1286
48V OUTPUT BOOST CONVERTER
LTC3862EGN, LTC3862EGN-1
DESCRIPTION
Demonstration circuit 1286A is DC/DC boost converter
featuring the LTC®3862EGN constant frequency current
mode boost controller. The DC1286A-A operates over 5V
to 36V input and provides 2A-5A of output current at
48V output. The DC1286A-B operates over 8V to 36V
input and provides 3A-5A of output current at 48V output. The 200kHz constant frequency operation results in
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 different output voltages. Please consult LTC factory for details.
The DC1286A has small circuit footprint. It is a high performance and cost effective solution for Telecom, Automotive and Power Over Ethernet applications.
Design files for this circuit board are available. Call
the LTC factory.
PowerPath is a trademark of Linear Technology Corporation
Table 1. Performance Summary
PARAMETER
CONDITION
Minimum Input Voltage
IOUT = 0A to 2A
VALUE
DC1286A-A
5V
DC1286A-B
8V
Maximum Input Voltage
IOUT = 0A to 5A
36V
VOUT
VIN = 12V, IOUT = 3A
48V ±3%
Typical Output Ripple VOUT
VIN = 12V, IOUT = 4A
400mVP–P
Nominal Switching Frequency
200kHz
QUICK START PROCEDURE
Demonstration circuit 1286A is easy to set up to evaluate the performance of the LTC3862. For proper measurement equipment setup refer to Figure 1 and follow
the procedure below:
2.
Check the Vcc Bias voltage-setting jumper JP5. Move
it into Vin position if required.
3.
Turn the input power source on and slowly increase
the input voltage. Be careful not to exceed 36V.
NOTE: When
measuring the input or output voltage ripple, care must be taken to minimize the length of 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.
Make sure that the input voltage Vin does not
exceed 36V. If higher operating voltage is required,
power components with higher voltage ratings should
be used. Also, Jumper JP5 will have to be moved to
12V position.
NOTE:
4.
Check for the proper output voltage of 48V.
If there is no output, temporarily disconnect the load
to make sure that the load is not set too high.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1286
48V OUTPUT BOOST CONVERTER
5.
Once the proper output voltage is established, adjust
the load and observe the output voltage regulation,
ripple voltage, efficiency and other parameters.
OPTIONAL BIAS CIRCUIT
The demo board DC1286A can be used for boosting
higher input voltages as well. In that case, the bias
power for LTC3862 has to be limited under 36V. An external power source can be used to accomplish this or
the optional bias regulator can be used by moving JP4
to 12V position. Since the power dissipation in bias
regulator Q5 depends on the size of MOSFETs, switching
frequency and voltage difference across Q5 all of the
factors need to be considered when selecting the appropriate device for Q5. Please refer to LTC3862 data sheet
for bias power requirements.
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1286
48V OUTPUT BOOST CONVERTER
CHANGING THE OUTPUT VOLTAGE
To set the output voltage lower than 48V, change the bottom voltage divider resistor connected to LTC3862 FB
pin.
To get higher than 48V output voltages MOSFETs and output diodes with higher voltage ratings may be required. Please contact LTC factory for details.
CONVERTER EFFICIENCY AND OUTPUT CURRENT
The DC1286A output current capability depends on the input voltage and proper cooling. Typical performance
of DC1286A-A is shown in Figure 3. The efficiency of DC1286A-B which is equipped with 10V gate drive version
of PWM controller LTC3862-1 is shown in Figure 4.
LTC3862 (DC1286A-A)
48V Boost Converter Efficiency
98%
96%
Efficiency
94%
92%
90%
5V in
12V in
88%
24V in
86%
0
1
2
3
4
5
6
Iout [A]
Figure 3. DC1286A-A Efficiency
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1286
48V OUTPUT BOOST CONVERTER
LTC3862-1 (DC1286A-B)
48V Boost Converter Efficiency
98%
Efficiency
96%
94%
92%
9V in
12V in
90%
24V in
88%
0
1
2
3
4
5
6
Iout [A]
Figure 4. DC1286A-B Efficiency
OUTPUT LOAD STEP RESPONSE
The load step response of DC1286A-A is very fast even though relatively small amount of output capacitance is
present at the output. If higher load steps need to be handled more output capacitance can be added in order to
keep the voltage transients at the desired level. The load step transients are shown in Figure 5.
Figure 5. Output Load Step Response
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1286
48V OUTPUT BOOST CONVERTER
5
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