International Rectifier IR3621 User manual

1
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Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
SPECIFICATION DATA
INTRODUCTION
IR3621EVALUATIONBOARDUSERGUIDE
Dual output using MOSFETs in SO8 package
INPUT/OUTPUT CONNECTIONS
Thefollowingistheinput/outputconnections:
Inputs:
JP1: Vin and Gnd
JU4:VCCandGnd
JU5:VCL
Outputs:
JP2:Vout1
JP5:Vout2
The connection points for dual output application are
shown in Figure 1. Connect the power supply cables
according to this figure, minimizing wire lengths to re-
duce losses in the wire. Test points J1, J2, J3 and J4
provideeasyconnectionforoscilloscopevoltageprobe
to monitor the inductor points for each PWM section
andoutputvoltages.
ThisreferenceboardisdesignedforDualoutput
configurationand will demonstrate the main features of
IC.
This user guide contains the schematic and bill of
materials,thedesignguidelines are described in data
sheet.
Application Data:
VIN = 12V
VOUT1 = 2.5V
IOUT1 = 10A
VOUT2 = 1.8V
IOUT2 = 10A
∆VOUT = 50mV
FS= 400KHz
Scope Probe connections:
J1andJ3:InductorpointforL2andL3
J2andJ4: Outputsfor Vout1 and Vout2
DESCRIPTION
TheIR3621ICcombines aDual synchronousBuckcon-
troller, providing a cost-effective,high performanceand
flexible solution. The IR3621 can be configured in 2-in-
dependent output or as a 2-phase mode. The 2-phase
configuration is ideal for high current applications. The
IR3621 features 180out of phase operation which re-
ducesthe required input/output capacitance. Other key
featuresoffered by this device include two independent
programmable soft starts, PreBias start up, program-
mable switching frequency up to 500KHz per phase,
external frequency synchronization and under voltage
lockout for proper start up. The current limit is provided
bysensingthe lower MOSFET's on-resistance for opti-
mumcost and performance.
PGOOD:JU1
SYNC:JU2

2Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
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Figure1 -Connection diagramofevaluation-board
CONNECTION DIAGRAM
LOAD
0-10A
LOAD
0-10A
PowerSupply 12V

3
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Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
The PCB is 4-layers FR4 board, the top layer is dedi-
catedforpower components,withcontrolMOSFETsand
SynchronousMOSFETs.TheseMOSFETs are SOIC-8
footprint. The input capacitors are all located close to
MOSFETs.The two output inductorsarelocatedclosed
to MOSFETs.
Thetwo mid-layers are dedicatedforAnalogand Power
ground,thesetwogroundsarekeptseparatedfromeach
otherand they areconnectedata single pointasshown
inFigure3.
All the decoupling capacitors, charge pump capacitor
and feedback components are located close to the IC.
The feedback resistors are tied to the output voltage at
the point of regulation and are located close to the IC.
LAYOUT
Figure2 -Toplayer of evaluation-board

4Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
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Figure3 - Midlayerof evaluation-board

5
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Rev.1.0
Dual_output_2xSO8
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Figure4-SchematicoftheevaluationBoard

6Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
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Ref Desig Description Value Qty Part# Manuf
2
2
1
2
2
2
8
8
6
9
1
1
1
1
1
2
2
4
2
1
10
4
8
7
4
3
4
Q1,Q4
Q2,Q5
U1
D1,D4
D2,D3
L2,L3
C3B-D,C4A-E
C27A-D,C28C-F
C14,C15,C16,C17,C18,C23
C3,C4,C5,C6,C7,C8,C9,C20,C21
C13
C11
R2
R5
R8
R12,R19
R27,R41
R29,R33,R42,R44
R31,R43
R45
R3,6,7,10,11,13,18,20,35,36
R1,4,9,32,
C1,2,C3A,C3E,C27E-F,C28A-B,
C10,12,19,22,24,25,26
J1,J2,J3,J4
JP1,JP2,JP5
JU1,JU2,JU4,JU5
MOSFET
MOSFET
Controller
Diode
Diode
Inductor
Cap,Poscap
Cap,Poscap
Cap,Ceramic
Cap,Ceramic
Cap,Ceramic
Cap,Ceramic
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Capacitor
Capacitor
ScopeProbe
Terminal
Jumper
IRF7821
IRF8113
IR3621M
BAT54S
BAT54A
ETQP6F1R1BFA
16TPB47M
6TPB330M
ECJ-2VF1E104Z
ECJ-2VF1C105Z
ECJ-2VB1H103K
ECJ-2VB1H822K
Any
131-5031-00
ED1973-ND
S1012-02-ND
30V,11mOhm
30V, 6mOhm
SynchronousPWM
Fast Switching
Fast Switching
1.1µH,16A
47µF,16V,70mΩ
330µF,6.3V,40mΩ
0.1µF, Y5V, 25V
1µF, Y5V, 16V
10nF,X7R, 50V
8.2nF,X7R,50V
6.2K
4.7K
22.6K
5.11K, 1%
2.15K, 1%
1K, 1%
1.24K,1%
49.9K,1%
Short,0Ω
Open
Open
Open
2-Posterminal
IR
IR
IR
IR
IR
Panasonic
Sanyo
Sanyo
Panasonic
Panasonic
Panasonic
Panasonic
Tektronix
Digi-Key
Digi-Key
BILL OF MATERIAL For Dual Output Application, Vin=12V,
Vout1=2.5V@10A, Vout2=1.8V@10A, Fs=400KHz

7
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Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
TYPICALOPERATING Waveforms
Test Conditions:
VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=400KHz, TA=Room Temp, No Air Flow
Unless otherwise specified.
Figure5-Startup wavforms for 2.5V output
Ch1: Vin, Ch2: Vout3, Ch3: SS1, Ch4:Vo1 (2.5V) Figure6-Start up wavforms for 1.8V output
Ch1: Vin, Ch2: Vout3, Ch3: SS2, Ch4:Vo2 (1.8V)
Figure7 - Startupwavforms
Ch1: Vin, Ch2: Vout3, Ch3: Vref Figure 8 - Vo1, Vo2 and PGood
Ch1: Vin, Ch2: Vo1, Ch3: Vo2, Ch4: PGood

8Rev.1.0
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6/7/2005
IRDC3621EVAL
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TYPICALOPERATING Waveforms
Test Conditions:
VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=400KHz, Ta=Room Temp, No Air Flow
Unless otherwise specified.
Figure 9 - 2.5V output
Ch1: Vin, Ch2: SS1, Ch3: Vo1, Ch4: PGood Figure 10 - 1.8V output
Ch1: Vin, Ch2: SS2, Ch3: Vo2, Ch4: PGood
Figure11 - Gatewaveformswith 180o
outof phase
Ch1:Hdrv1,Ch2:Hdrv2
Figure12 - 2.5V Waveforms
Ch1:Hdrv1, Ch2: Ldrv1,Ch3:Lx1, Ch4: InductorCurrent

9
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Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
TYPICALOPERATING Waveforms
Test Conditions:
VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=400KHz, Ta=Room Temp, No Air Flow
Unless otherwise specified.
Figure13 - 2.5V Waveforms
Ch1:Hdrv2, Ch2: Ldrv2,Ch3:Lx2, Ch4: InductorCurrent Figure14-1.8Voutputshorted
Ch1:Vo1,Ch2:SS2,Ch3:InductorCurrent
Figure15 - 2.5V output shorted
Ch1:Vo2,Ch2:SS1,Ch3:InductorCurrent Figure 16 - Prebias Start up
Ch1: SS1, Ch2: Vo1, Ch3: SS2, Ch4:Vo2

10 Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
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TYPICALOPERATING Waveforms
TestConditions:
VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=400KHz, Ta=Room Temp, No Air Flow
Unless otherwise specified.
Figure 17 - SS1 pin shorted to Gnd
Ch1:SS1, Ch2: Hdrv1,Ch3:Ldrv1, Ch4:Vo2 Figure 18 - SS2 pin shorted to Gnd
Ch1:SS2, Ch2: Hdrv2,Ch3:Ldrv2, Ch4:Vo1
Figure19-ExtrnalSynchronization
Ch1:Extrnal Clocl, Ch2: Hdrv1,Ch3:Hdrv2

11
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Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
TYPICALOPERATING Waveforms
Test Conditions:
VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=400KHz, Ta=Room Temp, No Air Flow
Unless otherwise specified.
Figure20 - LoadTransientRespons for Vo1
(Io=0 to 10A)
Ch1:Vo1,Ch4: Io1
Figure23 - LoadTransientRespons for Vo2
(Io=10 to 0A)
Ch1:Vo2,Ch4: Io2
Figure22 - LoadTransientRespons for Vo2
(Io=0 to 10A)
Ch1:Vo2,Ch4: Io2
Figure21 - LoadTransientRespons for Vo1
(Io=10 to 0A)
Ch1:Vo1,Ch4: Io1

12 Rev.1.0
Dual_output_2xSO8
6/7/2005
IRDC3621EVAL
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Figure 24- Efficiency for 2.5V and 1.8V outputs at room temperature no air flow.
Whenmeasuring one output, the other output was running at no load.
12V to 2.5V and 1.8V
45
50
55
60
65
70
75
80
85
90
0 2 4 6 8 10 12 14 16
Io(A)
Efficiency (%)
2.5V
1.8V
TYPICALPERFORMANCECURVES

13
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Figure 25- Thermal Images for Both Outputs at Vin:12V, Vout1:2.5V @ 10A, Vout2:1.8V
@10A.RoomTemperature,NoAir Flow
Test Point: 1) Sync FET for 2.5V output
2)Sync FET for 1.8V output
3) IR3621M IC.