DC1318A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1318
HIGH INPUT VOLTAGE AND HIGH CURRENT DENSITY STEP-DOWN CONVERTER
LTC3611EWP
DESCRIPTION
Demonstration circuit 1318 is a Synchronous StepDown Converter featuring the LTC®3611, the high efficiency, high density DC/DC regulator. The input voltage range of DC1318 is from 9V to 32V and the output voltage is jumper selectable from 1.5V to 3.3V,
although LTC®3611 has an input range from 4.5V to
32V and the output voltage range is from 0.6V. The
rated load current is 10A. The regulator includes the
controller and power MOSFETs in the 9mm by 9 mm
QFN package.
The constant on time valley mode current control
structure delivers very low duty cycle with excellent
load transient response. The MOSFET RDS(on) sensing eliminates external sensing resistor and improves
supply efficiency.
Discontinuous mode operation and continuous mode
at light load is also jumper selectable. A forced continuous control reduces noise and RF interference
while discontinuous control provides high efficiency
at light loads.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
9V
Maximum Input Voltage
32V
Output Voltage VOUT
Jumper selectable (open for 0.6V)
1.5V, 1.8V, 2.5V, 3.3V ± 2%
Maximum Continuous Output Current
De-rating is necessary for certain VIN, VOUT, and thermal
conditions, see datasheet
10ADC
Operating Frequency
Programmable
500kHz default
Efficiency
VIN=24V, VOUT =2.5V, IOUT =10A
87.8%, See Figure 3
VIN=24V, VOUT =3.3V, IOUT =10A
89.1%, See Figure 3
VIN=24V, VOUT =1.8V
See Figure 5
Load Transient
QUICK START PROCEDURE
Demonstration circuit 1318 is easy to set up to
evaluate the performance of the LTC3611. Please
refer to Figure 1 for proper measurement equipment setup and follow the procedure below:
1. Place jumpers in the following positions for
a typical 1.8VOUT application:
Vout Select
RUN
FCB
1.8V
ON
CCM
2. With power off, connect the input power
supply, load and meters as shown in Figure
1. Preset the load to 0A and Vin supply to
be less than 32V.
3. Turn on the power at the input. The output
voltage should be 1.8V ± 2%.
4. Once the proper output voltage is established, adjust the load within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other
parameters. Output ripple should be measured across the output bulk capacitor as
shown in Figure 2.
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1318
HIGH INPUT VOLTAGE AND HIGH CURRENT DENSITY STEP-DOWN CONVERTER
+
–
A
V
Vout
+
Vin
–
–
+
–
V
–
Iout
Load
0 -10A
Vin
A
+
–
+
Iin
put transient current can be monitored at
BNC connector J6 (5mV/A). Output voltage
transient response should be measured at
J5 with a BNC cable.
+
5. For optional load transient test, apply adjustable pulse signal between IOSTEP CLK
and GND pins. Pulse amplitude sets the current step. The pulse signal should have very
small duty cycle (<5%) to limit the thermal
stress on the transient load circuit. The out-
Optional
5V Bias
Figure 1. Proper Measurement Equipment Setup
(EXTVCC Bias Supply is Optional)
+
Input or Output Capacitor
Figure 2. Scope Probe Placements for Measuring Input or Output Ripple.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1318
HIGH INPUT VOLTAGE AND HIGH CURRENT DENSITY STEP-DOWN CONVERTER
32Vin Efficiency vs. Load Current
90%
90%
85%
85%
80%
80%
75%
75%
Efficiency
Efficiency
24Vin Efficiency vs. Load Current
70%
65%
65%
1.5Vo
1.5Vo
1.8Vo
60%
70%
60%
1.8Vo
2.5Vo
55%
2.5Vo
3.3Vo
55%
50%
0
1
2
3
4
5
6
7
8
9
10
Load Current (A)
11
12
3.3Vo
50%
0
1
2
3
4
5
6
7
8
9
10
11
12
Load Current (A)
Figure 3. Measured Supply Efficiency with Different VIN and VOUT
Figure 4. Thermal image of DC1318
Vin = 24V
Vout =1.8V
Iout = 10A
Tambient = 25°C, no forced airflow
Cross 1: MOSFETs
Cross 2: Inductor
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1318
HIGH INPUT VOLTAGE AND HIGH CURRENT DENSITY STEP-DOWN CONVERTER
Vo(AC)
200mV/DIV
Istep
4A/DIV
Vin = 24V
Vout =1.8V
2.5A to 7.5A LOAD STEP
Cout = 2 X 22uF ceramic, X5R, 0805, 2X100uF ceramic, X5R, 1812
Figure 5. Measured Load Transient Response (2.5-7.5A Step, 25% to 75%)
4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1318
HIGH INPUT VOLTAGE AND HIGH CURRENT DENSITY STEP-DOWN CONVERTER
5
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