IRDC3891 - International Rectifier

IRDC3891
SupIRBuck
TM
USER GUIDE FOR IRDC3891 EVALUATION BOARD
DESCRIPTION
The IR3891 is a dual synchronous buck
converter, providing a compact, high
performance and flexible solution in a small
5mm X 6mm Power QFN package.
Key features offered by the IR3891 include
internal Digital Soft Start, precision 0.5V
reference voltage, Power Good, thermal
protection,
programmable
switching
frequency, Enable input, input under-voltage
lockout for proper start-up, enhanced line/
load regulation with feed forward, external
frequency synchronization with smooth
clocking, internal LDO, pre-bias start-up,
output over voltage protection as well as open
feedback line protection.
Output over-current protection function is
implemented by sensing the voltage developed
across the on-resistance of the synchronous
rectifier MOSFET for optimum cost and
performance and the current limit is thermally
compensated.
This user guide contains the schematic and bill
of materials for the IRDC3891 evaluation board.
The guide describes operation and use of the
evaluation board itself. Detailed application
information for IR3891 is available in the
IR3891 data sheet.
BOARD FEATURES
• Vin = +12.0V
• Fs = 600kHz
• Vout1 = +1.8V @ 4A
Vout2 = +1.2V @ 4A
• L1 = 2.2uH
L2 = 1.5uH
• Cout1=4x22uF (ceramic 0805)
Cout2=4x22uF (ceramic 0805)
• Cin= 4x10uF (ceramic 1206) + 1x330uF (electrolytic)
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IRDC3891
CONNECTIONS and OPERATING INSTRUCTIONS
A well regulated +12.0V input supply should be connected to VIN+ and VIN-. A maximum 4A load should be
connected to VOUT+ and VOUT-. The connection diagram is shown in Fig. 1 and inputs and outputs of the
board are listed in Table I.
IR3891 has only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc
is required, then R3 should be removed and external Vcc should be applied between Vcc+ and Vcc- pins.
Vin pin (input of the LDO) and Vcc/LDO pins should be shorted together (populate R4) for external Vcc
operation.
The output of channel2 (Vout2) can follow the voltage at the Seq pin. For this purpose, The value of R5 and
R6 can be selected to provide the desired sequencing ratio between Seq input and Vout2. For normal
operation (non-sequencing) Seq pin should be left floating. Seq pin is internally pulled up to 3.3V.
Table I. Connections
Connection
Signal Name
VIN+
PVin (+12V)
VIN-
Ground of PVin
VOUT1+
Vout1 (+1.8V)
VOUT1-
Ground of Vout1
VOUT2+
Vout2 (+1.2V)
VOUT2-
Ground of Vout2
VCC+
VCC/LDO pin
VCC-
Connected to PGND
VSEQ
Sequence input
EN1, EN2
Enable input of each channel
Sync
Synchronous input
LAYOUT
The PCB is a 4-layer board. All of layers are 2 Oz. copper. The IR3891 and other components are
mounted on the top and bottom side of the board.
Power supply decoupling capacitors, the Bootstrap capacitor and feedback components are located
close to IR3891. The feedback resistors are connected to the output voltage at the point of regulation
and are located close to IR3891. To improve efficiency, the circuit board is designed to minimize the
length of the on-board power ground current path.
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IRDC3891
Connection Diagram
V OUT1
V OUT2
GROUND
GROUND
PGood1
SEQ
PGood2
Sync
Vsns1
EN1
Vsns2
EN2
VPG
Vcc/LDO_out
Vin
GROUND
Fig. 1: Connection diagram of IRDC3891 evaluation board (top and bottom)
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IRDC3891
R50 is the
Single point
connection
between AGND
and PGND.
Fig. 2: Board layout, top layer
Fig. 3: Board layout, bottom layer
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Fig. 4: Board layout, mid-layer I
Fig. 5: Board layout, mid-layer II
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Vin-
Vin-
Vin-
1
1
1
JUMPER1
J211
JUMPER1
J111
Vin
11.8k
R29
84.5K
R28
N/S
VSeq
EN2
N/S
C29
DIODE
SY NC D1
0
R5
2.2uF
C8
10uF
C112
R6
N/S
N/S
C7
10uF
10uF
C19
C211
C212
VCC Vcc+ Vcc-
11.8k
R19
N/S
N/S
EN1
C113
C213
R211
N/S
N/S
R111
84.5K
330uF/25V
R18
+ C1
Input ceramic: 1206
39.2K
R9
N/S
C9
C6
1.0uF
10uF
C111
N/S
R4
0
R3
Vsns2
9
8
7
6
5
4
3
2
1
R11
3.24k
10nF
C11
Vsns2
EN2
Rt/Sy nc
Seq
GND
Vcc/LDO
Vin
EN1
Vsns1
U1
150pF
C12
Vpg
R1
R7
49.9K N/S
VCC
PGood1
1
29
1
1
2
1
2
1
IR3891
25
Vin+
2.87K
10nF
C22 150pF
R21
C21
0.1uF
C24
0
R10
C14
0.1uF
NS
C27
Vin
0
R20
19
20
21
R27
2.87K
Vpg
0.1uF
C20
R26 4.02k
C26 NS
SW2
SW2
SW1
SW1
22
0.1uF
C10
R12
SW1
SW2
R23
2.87K
130
R24
2.2uH
L1
20
R15
B1
C123
22uF
C122
22uF
22uF
C124
22uF
C125
N/S
C126
N/S
C127
2200pF
C23
1.5uH
L2
A2
20
R25
B2
C223
22uF
C222
22uF
22uF
C224
22uF
C225
0
R50
N/S
C226
N/S
1
1
1
1
1
1
C221
0.1uF
1
1
Vout2 1
1
1
1
C121
0.1uF
Vout1
Vout2-
Vout2-
Vout2-
Vout2+
Vout2+
Vout2+
Vout1-
Vout1-
Vout1-
Vout1+
Vout1+
Vout1+
Agnd Agnd Agnd Agnd Agnd
V2
V1
Agnd Agnd
N/S
PGND PGND PGND
Agnd
N/S
C227
N/S
C129
C228 C229
N/S
C128
Output ceramic: 0805 (use 1206 footprint)
R22
A1
4.02k
SW11
SW22
PGood2
R2
49.9K
VCC
R8
N/S
Vpg
C13
2200pF
4.02k
R13
1.54k
130
1
R14
1
Fig.6: Schematic of the IRDC3891 evaluation board
10
1
1
31
FB1
FB2
30
Comp1
11
PGood1
Comp2
28
Boot2
13
PVin2
14
1
1
1
15
PGood2
12
Boot1
27
PVin1
26
PVin1
PVin2
24
PGND1
16
PGND1
PGND2
23
PGND1
PGND2
17
PGND2
18
4.02k
1
1
1
1
1
1
Vin+
NS
1
1
1
R16
1
R17
1.54k
1
C17
1
Vin
1
1
1
1
1
1
1
1
Vin+
1
C16 NS
1
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IRDC3891
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Bill of Materials
Item Qty
1
1
2
4
3
1
4
1
5
6
6
7
8
9
10
1
1
2
1
1
11
8
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
1
1
2
5
1
1
2
2
1
2
2
2
1
2
2
1
2
1
30
1
Vin=12.0V, Vout1=1.8V/4A, Vout2=1.2V/4A, Fsw=600KHz
Part Reference
Value
Description
Manufacturer
C1
330uF SMD Electrolytic F size 25V 20%
Panasonic
1206, 25V, X5R, 10%
C111 C112 C211 C212
10uF
TDK
0603, 25V, X5R, 10%
C6
1.0uF
Murata
0603, 16V, X5R, 20%
C8
2.2uF
TDK
C10 C14 C20 C24 C121
0.1uF
0603, 25V, X7R, 10%
Murata
C221
C11
10nF
0603, 50V, X7R, 10%
Murata
0603, 50V, NP0, 5%
Murata
C12
150pF
C13 C23
2200pF
0603, 50V, X7R, 10%
Murata
C21
10nF
0603, 50V, X7R, 10%
Murata
0603, 50V, NP0, 5%
Murata
C22
150pF
C122 C123 C124 C125
0805, 6.3V, X5R, 20%
22uF
TDK
C222 C223 C224 C225
L1
2.2uH
SMD 7.05x6.6x4.8mm,11.2mΩ
Cyntec
L2
1.5uH
SMD 7.05x6.6x4.8mm,6.0mΩ
Cyntec
Thick Film, 0603,1/10W,1%
R1 R2
49.9K
Panasonic
Thick Film, 0603,1/10W
R3 R5 R10 R20 R50
0
Panasonic
Thick Film, 0603,1/10W,1%
R9
39.2K
Panasonic
Thick Film, 0603,1/10W,1%
R11
3.24K
Panasonic
Thick Film, 0603,1/10W,1%
R12 R16
4.02K
Panasonic
Thick Film, 0603,1/10W,1%
R13 R17
1.54K
Panasonic
Thick Film, 0603,1/10W,1%
R14
130
Panasonic
Thick Film, 0603,1/10W,1%
R15 R25
20
Panasonic
Thick Film, 0603,1/10W,1%
R18 R28
84.5K
Panasonic
Thick Film, 0603,1/10W,1%
R19 R29
11.8K
Panasonic
Thick Film, 0603,1/10W,1%
R21
2.87K
Panasonic
Thick Film, 0603,1/10W,1%
R22 R26
4.02K
Panasonic
Thick Film, 0603,1/10W,1%
R23 R27
2.87K
Panasonic
Thick Film, 0603,1/10W,1%
R24
130
Panasonic
This is a simple jumper
J111 J211
jumper
D1
Schottky, 40V, SOD-523
Vishay
International
U1
IR3891
PQFN 5x6mm
Rectifier
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Part Number
EEV-FK1E331P
C3216X5R1E106K
GRM188R61E105KA12D
C1608X5R1C225M
GRM188R71E104KA01B
GRM188R71H103KA01B
GRM1885C1H151JA01D
GRM188R71H222KA01B
GRM188R71H103KA01B
GRM1885C1H151JA01D
C2012X5R0J226M
PCMB065T-2R2MS
PCMB065T-1R5MS
ERJ-3EKF4992V
ERJ-3GEY0R00V
ERJ-3EKF3922V
ERJ-3EKF3241V
ERJ-3EKF4021V
ERJ-3EKF1541V
ERJ-3EKF1300V
ERJ-3EKF20R0V
ERJ-3EKF8452V
ERJ-3EKF1182V
ERJ-3EKF2871V
ERJ-3EKF4021V
ERJ-3EKF2871V
ERJ-3EKF1300V
BAS40-02VGS08
IR3891MPBF
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IRDC3891
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Io1= Io2=0-4A, Room Temperature, No air flow
Fig. 7: Start up at 4A Load (Note 1)
Ch1:Vout1, Ch2:Vout2, Ch3:Vcc/LDO, Ch4:Vin
Fig. 8: Start up at 4A Load (Note 1)
Ch1:Vout1, Ch2:Vout2, Ch3:PGood1, Ch4: PGood2
Fig. 9: Start up with 1.05V Prebias, 0A Load
Ch1:Enable2, Ch2:Vout2, Ch4:PGood2
Fig. 10: Start up with 1.52V Prebias, 0A Load
Ch1:Enable1 , Ch2:Vout1, Ch4:PGood1
Fig. 11: Inductor switch node at 4A load / Channel
Ch1:SW1, Ch2:SW2
Fig. 12: Output Voltage Ripple, 4A load/channel (Note2)
Ch1: Vout1, Ch2: Vout2
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IRDC3891
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Room Temperature, No air flow
Fig. 15: Transient Response of channel1
0A-1.6A (0-40%), Ch1:Vout1 , Ch2:Vout2, Ch4: Iout1
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IRDC3891
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Room Temperature, No air flow
Fig. 16: Transient Response of channel2
0A-1.6A (0-40%), Ch1:Vout1 , Ch2:Vout2, Ch4: Iout2
Note1: Enable is tied to Vin via a resistor divider.
Note2: Vo ripple signal is taken across C125 and C225 capacitors.
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IRDC3891
Bode Plot, Channel1
Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Io1= Io2=4A, Room Temperature, No air flow
Fig.17: Bode Plot of CH1 at 4A load: Fo = 84.85 kHz; Phase Margin = 51.88º
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IRDC3891
Bode Plot, Channel2
Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Io1= Io2=4A, Room Temperature, No air flow
Fig.18: Bode Plot of CH2 at 4A load: Fo = 113.06 kHz; Phase Margin = 48.19º
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IRDC3891
Efficiency [%]
Efficiency and Power Loss of channel1
Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2 is disabled (EN2=low), Io1= 0-4A, Room Temperature, No air flow
94
92
90
88
86
84
82
80
78
76
74
72
70
68
0.0
0.5
1.0
1.5
2.0
Io [A]
2.5
3.0
3.5
4.0
0.5
1.0
1.5
2.0
Io [A]
2.5
3.0
3.5
4.0
1.0
0.9
Power Loss [W]
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.0
Fig.19: Efficiency and power loss vs. load current for channel1 (Vout1 = 1.8V)
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IRDC3891
Efficiency [%]
Efficiency and Power Loss of channel2
Vin=12.0V, Vcc/LDO=5.3V, Vout1 is disabled (EN1=low), Vout2=1.2V, Io2=0-4A, Room Temperature, No air flow
94
92
90
88
86
84
82
80
78
76
74
72
70
68
0.0
0.5
1.0
1.5
2.0
Io [A]
2.5
3.0
3.5
4.0
0.5
1.0
1.5
2.0
Io [A]
2.5
3.0
3.5
4.0
1.0
0.9
Power Loss [W]
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.0
Fig.20: Efficiency and power loss vs. load current for channel2 (Vout2 = 1.2V)
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IRDC3891
Thermal Image
Vin=12.0V, Vcc/LDO=5.3V, Vout1=1.8V, Vout2=1.2V, Io1= Io2=4A, Room Temperature, No air flow
Fig.21: Thermal Image at Io1=Io2=4A load
Test Point 1: IR3891, Test Point 2: Inductor_Ch1, Test Point 3: Inductor_Ch2
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IRDC3891
IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105
TAC Fax: (310) 252-7903
Visit us at www.irf.com for sales contact information
Data and specifications subject to change without notice.
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