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dc2111aabf
DEMO MANUAL
DC2111A-A/B
Description
LTC3774EUHE
4-Phase High Current Step-Down Converter
with Very Low DCR Inductor
Demonstration circuit DC2111A features the
LTC
®
3774
in
a 4-phase, high output current step-down converter with
sub-mΩ DCR sensing. This high performance converter
operates at a switching frequency of 400kHz over an input
voltage range of 10V to 14V. The 5mm × 5mm DrMOS
and 0.33µH/0.325mΩ inductor provide high efficiency
while supplying 30A per phase. The board comes in two
assembly types. The –A assembly provides a 1.2V/90A
converter with N+1 MOSFET failure protection and the –B
assembly provides a high efficiency 1.2V/120A converter.
1.2V/90A Converter with N+1 MOSFET Failure
Protection
The –A assembly is intended for high reliability applica-
tions which have a very low tolerance for down-time or
which operate in rugged environments. Each phase of the
1.2V/90A converter is protected by its own LTC4226-1
hot swap circuit on the input and an LTC4352 ideal diode
on its output. If an internal DrMOS MOSFET fails, then
that phase will be isolated from the rest of the circuit and
the converter will continue to operate with only a small
perturbation on the output and will provide the full rated
90A load. Once a fault is detected, the PWM signal for that
phase will be floated. This in turn will signal the DrMOS to
pull its TG and BG signals low. Examples of the converter’s
response to MOSFET failures can be seen in Figure 2 and
Figure 3. Further protection is provided by a dedicated 5V
bias supply for each phase. If the 5V bias for a given phase
is pulled down due to a DrMOS failure or other fault, the
5V bias for the other phases will not be affected.
In case of an overvoltage event, an external overvoltage
protection circuit will pull down the output. The LTC3774
does have its own crowbar type overvoltage protection,
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.
but the ideal diodes will prevent the bottom FETs from
pulling down the output once an overvoltage is detected.
The external OVP comparator will also provide overvolt-
age protection in case the voltage sense lines are shorted
or reversed.
For a 12V input, the –A assembly provides a full load ef-
ficiency of 89.3% and a peak efficiency of 90.6% which
occurs around 50% load.
1.2V/120A High Efficiency Converter
The –B assembly is a high efficiency 1.2V/120A 4-phase
converter. Given that it does not have the MOSFET failure
protection and redundancy of the –A assembly, it provides
higher efficiency and more output current. For a 12V input
it provides a full load efficiency of 90.6% and a peak ef-
ficiency of 93.1% which occurs at 55% load.
More Features
Both assembly types provide many features. These include:
•
Remote sensing
•
CLKIN and CLKOUT pins
•
PGOOD, RUN and TRACK/SS pins
•
Dynamic load circuit
•
Optional phase shedding circuit
The LTC3774 data sheet provide a complete description
of the IC operation and application information. The data
sheet must be read in conjunction with the quick start guide.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2111A-A/-B
