Description
DEMO MANUAL
DC2111A-A/B
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
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,
converter is protected by its own LTC4226-1
-
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
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.
-
-
-
:
dc2111aabf
1
DEMO MANUAL
DC2111A-A/-B
performance summary
Table 1. A Converter (TA = 25°C, No Airflow)
PARAMETER CONDITION VALUE
Minimum Input Voltage 10V
Maximum Input Voltage 14V
Output Voltage V
I
OUT(MAX)
Nominal Switching Frequency 400kHz
Efficiency, See Figure 6 V
Table 2. B Converter (TA = 25°C, No Airflow)
PARAMETER CONDITION VALUE
Minimum Input Voltage 10V
Maximum Input Voltage 14V
Output Voltage V
I
OUT(MAX)
Nominal Switching Frequency 400kHz
Efficiency, See Figure 7 V
OUT
VIN = 10V to 14V 90A
OUT
VIN = 10V to 14V 120A
Specifications are at TA = 25°C
I
= 0A to 90A, VIN = 10V to 14V 1.2V ± 1.5%
OUT
= 1.2V, I
OUT
I
= 0A to 120A, VIN = 10V to 14V 1.2V ± 1.5%
OUT
= 1.2V, I
OUT
= 90A, VIN = 12V 89.3% Typical
OUT
= 120A, VIN = 12V 90.6% Typical
OUT
2
dc2111aabf
Quick start proceDure
DEMO MANUAL
DC2111A-A/B
The evaluation setup for demonstration circuit 2111A is
shown in Figure 1. To test the board, follow the procedure
below:
1) With power off, connect the input supply, load and
meters as shown in the setup drawings. Preset the load
to 0A and V
2) Place the jumpers in the following positions:
JP1 RUN ON
JP2 MODE CCM
JP5 IDEAL DIODE
3) Set the input voltage to 12V.
4) Check the output voltage. The output voltage should be
within the regulation limits shown in the Performance
Summary table.
5) Next, apply full load and re-measure V
output voltage again to make sure it is within the regulation limits.
Adjust the input voltage and load current to the desired
6)
levels within their limits and observe the regulation,
output ripple, load step response, efficiency and other
parameters.
Note 1. To monitor the output voltage ripple, use the BNC
connectors labeled V
supply to be 0V.
IN
MODE
.
OUT
DIODE A ONLY
. Check the
OUT
Note 3. For loads less than 5A, some low level noise may
appear on the output of the –A assembly. This is due to the
normal operation of the ideal diodes and the slight current
sharing discrepancy between the phases. To avoid this,
place the DIODE jumper in the REV I ALLOWED setting.
This will allow reverse current to flow through the diodes
for clean output voltage ripple. However, the output will
not be protected from faults which short the switch node
to ground.
Dynamic Load Circuit (Optional)
Demonstration circuit 2111A provides a simple dynamic
load circuit consisting of a MOSFET and sense resistor.
To use the circuit, follow the steps below:
1. Connect the output of the pulse generator between
PULSE GEN and GND.
2. Connect the BNC labeled LOAD STEP to an oscilloscope.
3. Connect the BNC labeled V
4. Preset the amplitude of a pulse generator to 0V and
the duty cycle to 5% or less.
5. With the converter running, slowly increase the am
plitude of the pulse generator output to provide the
desired load
step signal is 2mV/A.
step pulse height. The scaling for the load
to an oscilloscope.
OUT
-
Note 2. Do not connect load between the VOS+ and VOS–
turrets. This could damage the converter. Only apply load
across the VOUT+ and VOUT– stud connectors on the
edge of the board.
dc2111aabf
3
DEMO MANUAL
DC2111A-A/-B
Quick start proceDure
COUT3
+
V
V
OUT
–
+ –
V
OUT
I
A
OUT
Figure 1. Proper Measurement Equipment Setup for DC2111A-A/-B
4
+ –
V
V
IN
I
A
IN
+
–
V
IN
SUPPLY
dc2111aab F01
dc2111aabf
Quick start proceDure
V
(AC)
OUT
50mV/DIV
V
IN4
10V/DIV
HiZB4
5V/DIV
PWM4
5V/DIV
VSW1
10V/DIV
VSW2
10V/DIV
VSW3
10V/DIV
VSW4
10V/DIV
DEMO MANUAL
DC2111A-A/B
50µs/DIV
dc2111aab F02
Figure 2. 1.2V/90A Converter with N+1 MOSFET Failure Protection. Top MOSFET of Phase 4 Shorted
Drain to Source with Full Load on the Output and a 12V Input. The Output Continues to Regulate with
Only a small Perturbation on the Output.
V
(AC)
OUT
50mV/DIV
V
IN1
10V/DIV
HiZB1
5V/DIV
PWM1
5V/DIV
VSW1
10V/DIV
VSW2
10V/DIV
VSW3
10V/DIV
VSW4
10V/DIV
Figure 3. 1.2V/90A Converter with N+1 MOSFET Failure Protection. Bottom MOSFET of Phase 1
Shorted Drain to Source with Full Load on the Output and a 12V input. The Output Continues to
Regulate with Only a Small Perturbation on the Output.
50µs/DIV
dc2111aab F03
dc2111aabf
5
Loading...