2
DEMO MANUAL
Rev. 0
DESCRIPTION
The 2220 ceramics in a metal frame are robust and con-
venient but may be replaced with an equivalent amount
of 1210 capacitance to minimize electrical noise. The
hybrid and bulk electrolytic capacitors stabilize the input
power. A combination of ceramic and aluminum polymer
capacitors are used at the power output in accordance
with design practice for the LT3763 primary controller.
DC2331A-A/DC2331A-B includes filters and filter options
for inputs to the LT8550 in accordance with data sheet
recommendations.
SHDN
voltage, switching frequency
and LT8550 ILIM current limit levels can all be adjusted
by resistors or resistor jumpers. DC2331A-A/DC2331A-B
comes with a housekeeping circuit that provides an 11.5V
input voltage to the LT8550. The housekeeping circuit
reduces the power dissipation that would otherwise
occur at high input voltages in regulator transistor Q21.
DC2331A-A/DC2331A-B uses resistors to sense inductor
current, but can be configured for DCR sensing of induc-
tor current.
DC2331A-A/DC2331A-B retains the features of the
LT3763 primary controller including:
• two inputs for analog control of the output current
regulation level
• output current monitoring
• fault indication.
A resistor divider combined with the CTRL1 output cur-
rent regulation level control makes the LT3763 current
limit occur before the LT8550 current limit to ensure
that the power sections share equally during output cur-
rent overload conditions. A resistor-NTC voltage divider
combined with the CTRL2 control reduces output current
when the PCB temperature reaches approximately 100°C.
A sense resistor for input current can be added and used
for input current regulation and monitoring. DC2331A-A
has placeholders for optional components that will allow
a voltage applied to the CTLV terminal to make modest
changes to the output voltage.
A high level of available output power without a corre-
sponding high level of design complexity or loss of con-
troller features makes the LT8550 attractive for high cur-
rent DC bus and battery systems in commercial, industrial
and automotive settings. DC2331A-A/DC2331A-B features
the LT8550EUKG in a thermally enhanced 52-pin 7mm x
8mm QFN package. The LT8550 and LT3763 data sheets
must be read in conjunction with this demo manual to
properly use or modify DC2331A-A/DC2331A-B.
Design files for this circuit board are available.
PERFORMANCE SUMMARY
Specifications are at T
A
= 25°C
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Minimum Input Voltage, V
IN
14
V
Maximum Input Voltage, V
IN
56
V
Output Voltage, V
OUT
R17=12.1k, R18=107k, R19=909
11.6
12.4
V
Maximum Output Current, I
OUT
DC2331A-A
70
A
Maximum Output Current, I
OUT
DC2331A-A + DC2331A-B
126
A
Output Current Limit, I
OUT
DC2331A-A, R50 = 100k, R82 = 150k, RSNS5 = 0.0025
80
A
Output Current Limit, I
OUT
DC2331A-A + DC2331A-B, R50 = 100k, R82 = 150k, RSNS5 = 0.0025
144
A
Efficiency
DC2331A-A, V
IN
= 24V, I
OUT
= 70A
97.50
%
Switching Frequency
250
kHz
