IRDC3846-P3V3 - International Rectifier

IRDC3846-P3V3
SupIRBuck
TM
USER GUIDE FOR IRDC3846 EVALUATION BOARD
DESCRIPTION
The IR3846 is a synchronous buck
converter, providing a compact, high
performance and flexible solution in a small
5mmx7mm QFN package.
Key features offered by the IR3846 include
internal Digital Soft Start, precision 0.6V
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, true differential
remote sensing and pre-bias start-up.
A thermally compensated 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.
This user guide contains the schematic and bill
of materials for the IRDC3846 evaluation board.
The guide describes operation and use of the
evaluation board itself. Detailed application
information for IR3846 is available in the
IR3846 data sheet.
BOARD FEATURES
• Vin = +12V, No Vcc required.
• Vout = +3.3V @ 0-35A
• Fs=300kHz
• L= 1.0uH
• Cin= 6x22uF (ceramic 1210) + 4x22uF (ceramic 1206) + 1x330uF (electrolytic)
• Cout= 5x120uF (SP) + 1x47uF (ceramic 0805)
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IRDC3846-P3V3
CONNECTIONS and OPERATING INSTRUCTIONS
A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 35A load should
be connected to VOUT+ and VOUT-. The inputs and output connections of the board are listed in Table I.
IR3846 needs 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 can be applied between Vcc+ and Vcc- pins. Vin
pin and Vcc pins should be shorted together for external Vcc operation by installing a 0 ohm resistor at R4.
The board is configured for remote sensing. If local sense is desired, R18 should be uninstalled and R19
should be installed instead.
External Enable signal can be applied to the board via exposed Enable pad and R100 should be removed
for this purpose.
Table I. Connections
Connection
Signal Name
VIN+
Vin (+12V)
VIN-
Ground of Vin
Vout+
Vout(+3.3V)
Vout-
Ground for Vout
Vcc+
Vcc Pin
Vcc-
Ground for Vcc input
Enable
Enable
PGood
Power Good Signal
AGnd
Analog ground
LAYOUT
The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3846 and most of the passive
components are mounted on the top side of the board.
Power supply decoupling capacitors and feedback components are located close to IR3846. The
feedback resistors are connected to the output of the remote sense amplifier of the IR3846 and are
located close to the IR3846. To improve efficiency, the circuit board is designed to minimize the length
of the on-board power ground current path. Separate power ground and analog ground are used and
may be connected together using a 0 ohm resistor at R71.
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IRDC3846-P3V3
CONNECTIONS and OPERATING INSTRUCTIONS
LAYOUT
The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3846 and most of the passive
components are mounted on the top side of the board.
Power supply decoupling capacitors and feedback components are located close to IR3846. The
feedback resistors are connected to the output of the remote sense amplifier of the IR3846 and are
located close to the IR3846. To improve efficiency, the circuit board is designed to minimize the length
of the on-board power ground current path. Separate power ground and analog ground are used and
may be connected together using a 0 ohm resistor at R71.
Vin
Gnd Gnd Vo
Top View
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Vin
Vp
PGD
PGood
PG_PU
PG_Pullup
Rt/Sy nc
N/S
D1
Sy nc
Sy nc
Vp
Vref
Vref
Vin
Agnd
1
Vcc-
1
Vcc+
1
4
OCSelect
2
VCC
Enable
1
3
C19
N/S
0 R3
4pin jumper
1
1
1
1
1
1
2
1
1
PVin
C5
N/S
N/S
R17
1.47K
Vsns
R101
7.5K
R100
49.9K
C71
22uF
C72
22uF
C73
22uF
C74
22uF
C75
22uF
C76
22uF
C77
22uF
C78
22uF
R14
R16
6.65K
R9
82.5K
RT/Sy nc
BOOT
OCset
RT/Sy nc
Enable
BOOT
NC2
NC1
PVin
C12
IR3846
C14
N/S
C13
3300pF
C11
1.8nF
2 R10
R15
20
R18
0
C16
N/S
20 Vin
0
R71
Vin
N/S R49
N/S R48
0 R47
0 R46
6
5
4
3
2
1
6
5
4
3
2
1
Vin-
Vin+
R110
10K
JUMPER 3
BODE2
C6
1uF
L1
C15
N/S
Vo_R_N
Vo_R_P
R113
N/S
Vin
2 Vout
N/S D2
11
C100-C124: 0805 / 1206 pads
Optional Pre-Bias test circuit
VPB
N/S
N/S
N/S
N/S
N/S
N/S
N/S
+ C126
120uF
N/S
N/S
+ C127
120uF
N/S
N/S
N/S
1
Vout_Adj
N/S R40
Ground and Signal ( “analog” ) Ground
N/S
N/S
N/S
N/S
+ C128
120uF
N/S
C40
N/S
M2
Vin
N/S
N/S
Optional "1-bit VID" circuit
N/S
N/S R41
FB
N/S
+ C129
120uF
N/S
C119 C120 C121 C122 C123 C124
N/S
5 x 120uF / 6.3V / SP Capacitor
+ C125
120uF
47uF N/S
C109 C110 C111 C116 C117 C118
N/S
C100 C101 C102 C103 C104 C105 C106 C107 C108 C113 C114 C115 C112
1 x 47uF / 0805 / 6.3V / Ceramic Capacitor
Single point of connection between Power
Vout
Vp
R112
N/S
VDDQ
R111
10K
1uH
330uF / 25V / Electrolytic Capacitor
330uF
+ C81
0 R115
N/S R4
C8
10uF
C80
22uF
N/S R70
0 R118
158 R117
715 R116
17 Vref
18
19 PGD
C17
100pF
VCC
21 VCC
22
23
BODE1
JUMPER 2
R19
N/S
S_Ctrl
Vref
Vp
PGD
Vin
VCC
NC3
NC4
SW
24
SW
C79
22uF
1
Fig. 1: Schematic of the IRDC3846 evaluation board
7.32K R13
549 R12
30K R11
36pF
R114
N/S
7
6
5
4
3
2
1
U1
0.1uF C10
BOOT
4 x 22uF / 1206 / 25V / Ceramic Capacitor
6 x 22uF / 1210 / 25V / Ceramic Capacitor
C70
0.1uF
26
PVin
VCC
C71-C80: 0805 / 1206 pads
1
1
Vin
PG_PU
PVin
FB
Vin
FB
Vsns
8
Vsns
9
FB
Comp
10
RSo
11
PGND
12
NC5
LGND
13
S_Ctrl
14
1
RS15
RS+
16
1
1
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1
R46-R49: 1206 pads
N/S
C130
6
5
4
3
2
1
6
5
4
3
2
1
Vout-
Vout+
Vout
IRDC3846-P3V3
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IRDC3846-P3V3
Schematic for Transient Load set up
ExtLoadCtrl
3
1
VCC
N/S R34
N/S
2
1
S3
SW
N/S R35
N/S R36
C30
N/S
U2
N/S R30
1
2
3
4
VS
VS
IN
OUT2
N/A OUT1
GND GND
8
7
6
5
N/S R38
N/S R39
MIC4452/SO8 N/S
R31
N/S
C31
N/S
D3
N/S
R32
N/S
Vout
M1
IRF6721 N/S
D4
N/S
N/S R37
1
C32
N/S
Vout
R33
N/S
I-Monitor
Vo_R_P
C33
0.1uF
Vo_R_N
Optional transient load circuit
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IRDC3846-P3V3
Bill of Materials
Item Qty Part Reference
Value
1
4 C74 C75 C79 C80 22uF
C71 C72 C73 C76
22uF
2
6
C77 C78
C6
1uF
3
1
C8
10uF
4
1
5
3
C10 C33 C70
0.1uF
6
1
C11
1.8nF
7
1
C12
36pF
8
1
C13
3300pF
9
1
C17
100pF
Description
1206, 25V, X5R, 10%
Manufacturer
Murata
Part Number
GRM31CR61E226KE15L
1210, 25V, X5R, 20%
Taiyo Yuden
TMK325BJ226MM-T
0603, X5R, 25V, 20%
0603, X5R, 10V, 20%
0603, 25V, X7R, 10%
0603, 50V, X7R, 10%
0603, 50V, NP0, 5%
0603, 50V, X7R, 10%
0603, 50V, NP0, 5%
SMD Elecrolytic, Fsize,
25V, 20%
1uH, DCR=0.93mohm
0805, 6.3V, X5R, 20%
TDK
TDK
Murata
Murata
Murata
Murata
Murata
C1608X5R1E105M
C1608X5R1A106M
GRM188R71E104KA01D
GRM188R71H182KA01D
GRM1885C1H360JA01D
GRM188R71H332KA01D
GRM1885C1H101JA01D
Panasonic
EEE-FK1E331P
Coilcraft
TDK
XAL1580-102ME_
C2012X5R0J476M
Panasonic
EEF-UD0J121R
10
1
11
12
1
1
13
5
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
4
1
1
1
1
1
1
1
1
2
1
1
1
2
1
1
30
1
Jumper
31
2
Vin+ Vout+
RED
32
2
Vin- Vout-
BLACK
SCREW TERMINAL
33
1
U1
IR3846
IR3846 5mm X 7mm
C81
330uF
L1
1uH
C109
47uF
C125 C126 C127
120uF
C128 C129
R3 R18 R115 R118
0
R9
82.5K
R10
2
R11
30K
R12
549
R13
7.32K
R16
6.65K
R17
1.47K
R15
20
R46 R47
0
R71
0
R100
49.9K
R101
7.5K
R110 R111
10K
R116
715
R117
158
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6.3V, 20%,15mΩ
0603,1/10W, Jumper
Vishay/Dale
0603,1/10W,1%
Panasonic
0603,1/10W,5%
Panasonic
0603,1/10W,1%
Panasonic
0603,1/10W,1%
Panasonic
0603,1/10W,1%
Panasonic
0603,1/10W,1%
Panasonic
0603,1/10W,1%
Panasonic
0603,1/10W,1%
Vishay/Dale
1206,1/4W, Jumper
Yageo
0402, 1/16W, Jumper
Yageo
0603,1/10 W,1%
Panasonic
0603,1/10 W,1%
Panasonic
0603,1/10 W,1%
Panasonic
0603,1/10 W,1%
Panasonic
0603,1/10 W,1%
Panasonic
PLUG 40 POS DBL ROW
Omron
STR
Electronics Inc.
Keystone
SCREW TERMINAL
Electronics
Keystone
Electronics
International
Rectifier
CRCW06030000Z0EA
ERJ-3EKF8252V
ERJ-3GEYJ2R0V
ERJ-3EKF3002V
ERJ-3EKF5490V
ERJ-3EKF7321V
ERJ-3EKF6651V
ERJ-3EKF1471V
CRCW060320R0FKEA
RC1206JR-070RL
RC0402JR-070RL
ERJ-3EKF4992V
ERJ-3EKF7501V
ERJ-3EKF1002V
ERJ-3EKF7150V
ERJ-3EKF1580V
XG8W-4041-ND
8199-2
8199-3
IR3846MPBF
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IRDC3846-P3V3
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=3.3V, Io=0A-35A, Fsw=300kHz, Room Temperature, No air flow
Fig. 2: Start up at 35A Load
Ch1:Vin, Ch2:Vo, Ch3:PGood, Ch4:Enable
Fig. 4: Start up with 2.97V Pre Bias, 0A Load
Ch2:Vo, Ch3:PGood
Fig. 6: Inductor node at 35A load
Ch2:LX
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Fig. 3: Start up at 35A Load
Ch1:Vin, Ch2:Vo, Ch3:PGood, Ch4:Vcc
Fig. 5: Output Voltage Ripple, 35A load
Ch1: Vo
Fig. 7: Short (Hiccup) Recovery
Ch2:Vo, Ch3:PGood, Ch4:Io
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IRDC3846-P3V3
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=3.3V, Io=0A-17.5A, Fsw=300kHz, Room Temperature, No air flow
Fig. 8: Transient Response, 0A to 17.5A step (2.5A/us)
Ch2:Vo, Ch4:Io
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IRDC3846-P3V3
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=3.3V, Io=17.5A-35.0A, Fsw=300kHz, Room Temperature, No air flow
Fig. 9: Transient Response, 17.5A to 35A step (2.5A/us)
Ch2:Vo, Ch4:Io
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IRDC3846-P3V3
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=3.3V, Io=35A, Fsw=300kHz, Room Temperature, No air flow
Fig. 10: Bode Plot at 35A load: Fo = 36.9kHz; Phase Margin = 56.6º; Gain Margin = -24.7dB
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IRDC3846-P3V3
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=3.3V, Io=0A-35A, Fsw=300kHz, Room Temperature, No air flow
97
95
Efficiency [%]
93
91
89
87
85
83
81
79
77
0
5
10
15
20
25
30
35
25
30
35
Io [A]
Power Loss [W]
Fig.11: Efficiency versus load current
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
5
10
15
20
Io [A]
Fig.12: Power loss versus load current
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IRDC3846-P3V3
THERMAL IMAGES
Vin=12.0V, Vo=3.3V, Io=35A, Fsw=300kHz, Room Temperature, LFM = 100
Fig. 13: Thermal Image of the board at 35A load
IR3846: 74.10C
Inductor: 53.20C
Ambient: 24.80C
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IRDC3846-P3V3
THERMAL IMAGES
Vin=12.0V, Vo=3.3V, Io=35A, Fsw=300kHz, Room Temperature, LFM = 200
Fig. 14: Thermal Image of the board at 35A load
IR3846: 69.70C
Inductor: 49.40C
Ambient: 24.10C
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IRDC3846-P3V3
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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