R
EFERENCE
D
ESIGN
Overview
This reference design is capable of delivering up to a current of
160A with the enclosed heatsink attached at an ambient
temperature of 60ºC with 400LFM or an ambient temperature of
45ºC with 200LFM of airflow. Performance graphs and waveforms
are provided in figures 1–9. The figures and table in pages 5 – 8
are provided as a reference design to enable engineers to very
quickly and easily design a 4-phase converter. Refer to the data
sheet for the controller listed in the bill of materials in order to
optimize this design to your specific requirements. A variety of other
controllers may also be used, but the design will require layout and
control circuit modifications.
IRDCiP2003A-C
International Rectifier
•
233 Kansas Street, El Segundo, CA 90245 USA
IRDCiP2003A-C: 1MHz, 160A, Synchronous Buck
Converter Using iP2003A
Demoboard Quick Start Guide
Initial Settings:
The output is set to 1.3V, but can be adjusted from 0.8V to 3.3V by changing the voltage divider values of R3 and R32 according
to the following formula:
R3 = R32 = (24.9k x 0.8) / (VOUT - 0.8)
The switching frequency per phase is set to 1MHz with the frequency set resistor R4. This creates an effective output frequency of
4MHz. The graph in figure 11 shows the relationship between R4 and the switching frequency per phase. The frequency may be
adjusted by changing R4 as indicated; however, extreme changes from the 1MHz set point may require redesigning the control
loop and adjusting the values of input and output capacitors. Refer to the SOA graph in the iP2003A datasheet for maximum
operating current at different conditions.
Procedure for Connecting and Powering Up Demoboard:
1. Apply input voltage across (+12V) across VIN and PGND.
2. Apply load across VOUT pads and PGND pads.
3. Adjust load to desired level. See recommendations below.
IRDCiP2003A-C Recommended Operating Conditions
(refer to the iP2003A datasheet for maximum operating conditions)
1
Input voltage:
5V - 12V
Output voltage:
0.8 - 3.3V
Switching Freq:
1MHz per phase, 4MHz effective output frequency.
Output current:
This reference design is capable of delivering up to 160A with the enclosed heatsink attached, at an
ambient temperature of 60ºC with 400LFM of airflow, or an ambient temperature of 45ºC with 200LFM of
airflow.
1
Note: If Vin = 5V, then connect Vin to test point TP3 and Terminal T1 and remove jumper J1. Refer to schematic for details.
Additionally, the threshold of the POR circuit should be adjusted to allow the supply to sequence properly.
12/03/04
IRDCiP2003A-C_ ____
55.0
_____
86%
85%
84%
83%
82%
81%
80%
50.0
45.0
40.0
35.0
Power Loss (W)
V
IN
= 12V
V
OUT
= 1.3V
f
SW
= 1MHz
T
A
= 25
°C
Efficiency (%)
30.0
79%
78%
77%
76%
75%
25.0
20.0
15.0
74%
73%
72%
10.0
V
IN
= 12V
V
OUT
= 1.3V
f
SW
= 1MHz
T
A
= 25
°C
0
20
40
60
80
Output Current (A)
100
120
140
160
5.0
71%
70%
0
20
40
60
80
Output Current (A)
100
120
140
160
0.0
Fig. 1: Power Loss vs. Current
Fig. 2: Efficiency vs. Current
Phase Margin = 61°
Cross-Over Freq. = 106kHz
V
IN
= 12V
V
OUT
= 1.3V
I
OUT
= 160A
f
SW
= 1MHz
T
A
= 25
°C
Fig. 3: Bode Plot
V
IN
= 12V,
V
OUT
= 1.3V
I
OUT
= 160A,
f
SW
= 1MHz
T
A
= 25°C
V
IN
= 12V,
V
OUT
= 1.3V
I
OUT
= 160A,
f
SW
= 1MHz
T
A
= 25°C
Ripple = 90mVp-p
Ripple = 7.0mVp-p
Fig. 4: Input Voltage Ripple Waveform
Fig. 5: Output Voltage Ripple Waveform
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2
_____________
100.0%
99.8%
99.6%
Output Voltage Accuracy (%)
99.4%
99.2%
99.0%
98.8%
98.6%
98.4%
98.2%
98.0%
0
20
40
60
80
Output Current (A)
__IRDCiP2003A-C
V
IN
= 12V
V
OUT
= 1.3V
f
SW
= 1MHz
T
A
= 25
°C
100
120
140
160
Fig. 6: Output Voltage Accuracy vs. Current
V
IN
= 12V
V
OUT
= 1.3V
I
OUT
= 160A
f
SW
= 1MHz
T
A
= 25°C
Ch. 1: V
IN
2V/div
Ch. 1: V
IN
2V/div
V
IN
= 12V
V
OUT
= 1.3V
I
OUT
= 160A
f
SW
= 1MHz
T
A
= 25°C
Ch. 2: V
OUT
0.5V/div
Ch. 2: V
OUT
0.5V/div
Fig. 7: Power Up Waveform
Fig. 8: Power Down Waveform
Ch. 1: V
OUT
1V/div
V
IN
= 12V
V
OUT
= 1.3V
f
SW
= 1MHz
T
A
= 25°C
Hiccups
until short
circuit is
removed
Short
circuit at
start-up
Ch. 2: I
OUT
50A/div
Fig. 9: Short Circuit Condition Waveform
3
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IRDCiP2003A-C_ ____
*>120.0°C
120.0
100.0
80.0
60.0
40.0
Airflow direction
V
IN
= 12V
V
OUT
= 1.3V
I
OUT
= 160A
f
SW
= 1MHz
T
A
= 45°C
Airflow = 200LFM
Max
70.7°C
_____
Board Temperature @ 1mm
from edge of module:
T
PCB
(U2):
T
PCB
(U3):
T
PCB
(U4):
T
PCB
(U5):
83.4°C
82.7°C
82.3°C
79.2°C
*<21.3°C
*>120.0°C
120.0
100.0
80.0
60.0
40.0
V
IN
= 12V
V
OUT
= 1.3V
I
OUT
= 160A
f
SW
= 1MHz
T
A
= 60°C
Airflow = 400LFM
Max
78.5°C
Board Temperature @ 1mm
from edge of module:
T
PCB
(U2): 88.9°C
T
PCB
(U3): 87.5°C
T
PCB
(U4): 87.3°C
T
PCB
(U5): 85.1°C
Airflow direction
*<21.3°C
Fig. 10: Thermal Images With Board and Heatsink Temperatures
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4
_____________
Adjusting the Over-Current Limit
__IRDCiP2003A-C
R5, R7, R8, and R9 are the resistors used to adjust the over-current trip point. The trip point is a function of the controller and
corresponds to the per phase output current indicated on the x-axis of Fig. 11. For example, selecting 3.65k resistors will set the
trip point of each phase to 66A. (Note: Fig. 11 is based on iP2003A, TJ = 125
°
C. The trip point will be higher than expected if the
reference board is cool and is being used for short circuit testing.)
3.7
3.6
3.5
3.4
3.3
3.2
R
ISEN
(kΩ)
3.1
3.0
2.9
2.8
2.7
2.6
2.5
2.4
43
45
47
49
51
53
55
57
59
61
63
65
67
Over-Current Trip Point (per Phase)
Fig. 11: R
ISEN
vs. Current (per Phase)
100
R4 (k
Ω
)
10
100
1000
Output Frequency (kHz) (per Phase)
Fig. 12: R4 vs. Frequency (per Phase)
5
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