DEMO MANUAL DC1734A
LT8582
Dual 3A Boost/Inverting/SEPIC
DC/DC Converter
DESCRIPTION
Demonstration circuit 1734A features the dual channel
LT
®
8582 in boost and inverting regulator configurations.
The circuit is designed to convert a 5V to 10V input source
to 12V at 900mA and –12V at 590mA as shown in Table 1.
Table 1. Maximum Guaranteed Output Currents
V
IN
(V)
4.5
5.0
5.5
MAX I
LOAD1
(mA)
775
900
1000
MAX I
LOAD2
(mA)
540
590
625
To change the topology of channel 1 from boost to invert-
ing: Replace D1 with a capacitor similar to C12, replace
C2 with a diode similar to D3, placing the diode so that
its cathode is connected to ground, and replace R16 with
an inductor similar to L3.
To change the topology of channel 2 from inverting to boost:
Replace C12 with a diode similar to D1, placing the diode so
that its anode is connected to L2, replace D3 with a capacitor
similar to C2, and replace L3 with a jumper resistor similar
to R16. However, this configuration will not be output short
protected since it lacks the external disconnect MOSFET.
Each channel of the LT8582 includes a 42V master and slave
power switch combination with 3A total current and can easily
be configured as a boost, SEPIC, inverting or flyback converter.
The LT8582 has a 2.5V to 22V operating input range, UVLO,
soft-start, programmable switching frequency and many other
features. The LT8582 data sheet gives a complete description
of the part, its operation and application information. The
data sheet must be read in conjunction with this quick start
guide for working on or modifying the demo circuit 1734A.
Design files for this circuit board are available at
http://www.linear.com/demo
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
To limit the temperature rise of the chip to 40°C, on the
demo board with no air flow, the maximum combined
output power is 15W. Additional input bulk capacitance
may be needed, subject to source impedance.
DC1734A is designed to survive output short circuit events.
On the positive channel an external disconnect MOSFET
protects the boost converter. The negative channel is
based on dual inductor inverting topology and does not
need the external MOSFET as it is inherently output short
protected. The circuit board includes an option to install
the external disconnect MOSFET at the input side of the
positive channel. To use it, remove Q1 and R1 from the
top of the circuit board and install them on the back, in
the location of Q2 and R2. Then, place a jumper from Q1’s
source to drain and cut the top copper as shown in Figure 6.
PERFORMANCE SUMMARY
SYMBOL
V
IN
V
OUT1
PARAMETER
Input Supply Range
Channel 1 Output Voltage Accuracy
Channel 1 Output Voltage Ripple
Channel 1 Efficiency
Channel 1 Efficiency
V
OUT2
Channel 2 Output Voltage Accuracy
Channel 2 Output Voltage Ripple
Channel 2 Efficiency
Channel 2 Efficiency
f
S
Switching Frequency
(T
A
= 25°C)
CONDITIONS
V
IN
= 5V to 10V, I
LOAD
= 900mA
V
IN
= 5V, I
LOAD
= 900mA
V
IN
= 5V, I
LOAD
= 900mA
V
IN
= 10V, I
LOAD
= 900mA
V
IN
= 5V to 10V, I
LOAD
= 590mA
V
IN
= 5V, I
LOAD
= 590mA
V
IN
= 5V, I
LOAD
= 590mA
V
IN
= 10V, I
LOAD
= 590mA
–11.5
MIN
5
11.6
12
60
86
92
–12
56
83
85
1
–12.3
TYP
MAX
10
12.4
UNITS
V
V
mV
PP
%
%
V
mV
PP
%
%
MHz
dc1734af
1
DEMO MANUAL DC1734A
QUICK START PROCEDURE
Demonstration circuit DC1734A is easy to set up to evalu-
ate the performance of the LT8582. Refer to Figure 1 for
proper measurement equipment set-up and follow the
procedure below.
To measure voltage ripple, care must be taken to avoid a
long ground lead on the oscilloscope probe. Remove the
oscilloscope probe end cap and ground lead and set the
bandwidth limit on the oscilloscope. Measure the input
voltage ripple by touching the probe tip and ground directly
across V
IN
and GND terminals. See Figure 2 for proper
input voltage ripple measurement technique. Measure the
positive output voltage ripple by touching the probe tip
directly across output capacitor C16 terminals, connect-
ing the probe ground terminal to the board’s GND plane.
Measure the negative output voltage ripple by touching the
probe tip directly across output capacitor C9, connecting
the probe ground terminal to the board’s GND plane. See
Figure 3 for proper output voltage ripple measurement
technique.
1. Place the on board jumpers in the following positions:
To activate boost converter:
JP1
ON
To activate inverting converter:
JP2
ON
2. With power off, connect the input power supply to V
IN
and GND. Apply 7.5V to the input (source must have
greater than 10A capability).
3. Check for the proper output voltages.
NOTE.
If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
4. Once the proper output voltage is established, adjust
the load and the input voltage within the operating
range and observe the output voltage regulation, ripple
voltage, efficiency and other parameters. The efficiency
graphs of the two channels are provided in Figure 4
and Figure 5.
Figure 1. Proper Measurement Equipment Setup
dc1734af
2
Talking
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