IRDC3847-P1V2 - International Rectifier

IRDC3847-P1V2
SupIRBuck
TM
USER GUIDE FOR IR3847 EVALUATION BOARD
DESCRIPTION
The IR3847 is a synchronous buck
converter, providing a compact, high
performance and flexible solution in a small
5mmx6mm QFN package.
Key features offered by the IR3847 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 IR3847 evaluation board.
The guide describes operation and use of the
evaluation board itself. Detailed application
information for IR3847 is available in the
IR3847 data sheet.
BOARD FEATURES
• Vin = +12V (+ 13.2V Max), No Vcc required.
• Vout = +1.2V @ 0-25A
• Fs=600kHz
• L= 0.215uH
• Cin= 7x22uF (ceramic 1206) + 1x330uF (electrolytic)
• Cout=10x47uF (ceramic 0805)
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IRDC3847-P1V2
CONNECTIONS and OPERATING INSTRUCTIONS
A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 25A load should
be connected to VOUT+ and VOUT-. The inputs and output connections of the board are listed in Table I.
IR3847 needs only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc
is required, then R33 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 R35.
The board is configured for remote sensing. If local sense is desired, R8 should be uninstalled and R16
should be installed instead.
External Enable signal can be applied to the board via exposed Enable pad and R18 should be removed for
this purpose.
Table I. Connections
Connection
Signal Name
VIN+
Vin (+12V)
VIN-
Ground of Vin
Vout+
Vout(+1.2V)
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 IR3847 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 IR3847. The
feedback resistors are connected to the output of the remote sense amplifier of the IR3847 and are
located close to the IR3847. 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 one of three possible locations. It is preferred to
use one of R43 or R44.
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IRDC3847-P1V2
CONNECTIONS and OPERATING INSTRUCTIONS
LAYOUT
The PCB is a 6-layer board. All of layers are 2 Oz. copper. The IR3847 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 IR3847. The
feedback resistors are connected to the output of the remote sense amplifier of the IR3847 and are
located close to the IR3847. 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 one of three possible locations. It is preferred to
use one of R43 or R44.
Vin
Gnd Gnd Vo
Top View
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3
1
D2
N/S
11
2 Vout
PG_PU
PG_Pullup
N/S
C9
1
Vout_Adj
R26
N/S
C52
N/S
M3
Fb
Vcc-
4
OCSelect
2
1
3
R9
39.2K
19
28
30
31
33
Rt/Sy nc 4
5
Vp
NC0
NC1
NC2
NC3
NC4
Rt/Sy nc
OCSelect
PGD
Vcc
Comp
FB
RSo
Vref
IR3847
1
N/S
R2
4.22K
N/S
R21
C8
Vsns
2200pF
4.22K
127
C50
N/S
0.1uF
C37
C39
0
C56
N/S
C54
N/S
R28
1uF
C55
N/S
C25
0.1uF
R3
Fb
13
6
20
21
22
23
24
25
32
2
26
C57
22uF
R4
RS+
Vsns
SW
SW
SW
SW
SW
SW
SW
Boot
PGnd
Vin
R33
0
49.9K
R35
VCC
R18
N/S
C38
C24
0.1uF
C7
22uF
BODE
JUMPER 2
R6
20
0
R11
N/S
R12
0
R10
4.22K
R32
C6
22uF
C5
22uF
L1
R20
N/S
Vout
Vsns
N/S
C45
47uF
47uF
47uF
C20
47uF
C19
47uF
C18
0 ohm
47uF
C17
47uF
C16
N/S
C44
0
R44
N/S
R43
N/S
C42
N/S N/S
C43 C40
N/S
C41
47uF
C21
47uF
C22
+ C35
N/S
+ C36
N/S
Ground and Signal ( “analog” ) Ground
+ C51
N/S
C14
0.1uF
Vin-
Vin+
Vout
6
5
4
3
2
1
6
5
4
3
2
1
+ C34
N/S
47uF
C15
25V 330uF
C2 + C1
22uF
330uF
R30
0 ohm
10 x 47uF / 0805 / 6.3V Ceramic
N/S
N/S
0.1uF
C28
C3
22uF
PVin
R31
Single point of connection between Power
N/S
R16
Vo_R_N
Vo_R_P
4.22K
R15
C29
C33 C30
C27
C4
22uF
7 x 22uF / 1206 / 25V Ceramic
C31
N/S
215nH PCDC1008-R215EMO
SWs
C32
N/S
Fig. 1: Schematic of the IR3847 evaluation board
Agnd
4pin jumper
C68
N/S
R17 10K
16
PGD
8
7
9
U3
PG_PU R29 10K
Vcc+
8.2nF
C26
C11 160pF
0
R8
R19
7.5K
18
C66
10uF
VCC
1.91K
R1
Optional "1-bit VID" circuit
N/S
N/S
R27
PGD
PGood
Vp
Vp
R41
N/S
R40
N/S
Vp
VDDQ
Optional Pre-Bias test circuit
VPB
Rt/Sy nc
N/S
D3
Sy nc
Sy nc
100pF
C10
1
1
2
1
Vref
1
1
1
15
Vp
Vref
1
1
1
17
Vin
1
3
Enable
Vref
14
LGnd
11
1
PVin
PGnd
PGnd
PGnd
10
27
29
RS12
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1
Enable
6
5
4
3
2
1
6
5
4
3
2
1
Vout-
Vout+
IRDC3847-P1V2
4
IRDC3847-P1V2
Schematic for Transient Load set up
Vout
VCC
3
1
R22
ExtLoadCtrl
R23
2
1
N/S
N/S
S3
SW
N/S
R24
Vo_R_P
N/S
R36
N/S
U2
1
2
3
4
R39
N/S
C46
N/S
C49
N/S
VS
VS
IN
OUT2
N/A OUT1
GND GND
8
7
6
5
MIC4452/SO8 N/S
R37
N/S
R53
100
R54
100
D7
ZHCS350
D6
ZHCS350
R25
M1
IRF6721 N/S
Vout
N/S
C47
N/S
C48
N/S
1
R38
N/S
C58
N/S
C59
N/S
C60
N/S
C61
N/S
C62
22uF
C65
N/S
C64
N/S
C63
N/S
I-Monitor
Vo_R_N
Optional transient load circuit
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IRDC3847-P1V2
Bill of Materials
Item Quantity
Part Reference
Value
C2 C3 C4 C5 C6 C7
22uF
C57
1
7
2
1
3
6
4
5
1
1
6
10
7
8
9
10
11
12
13
14
1
1
1
1
1
1
1
1
15
7
16
17
18
19
20
21
22
1
1
2
2
1
1
2
23
1
Jumper
24
25
26
2
2
1
Vin+ Vout+
Vin- VoutU1
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C1
330uF
C9 C14 C24 C25
0.1uF
C37 C33
C8
2200pF
C11
160pF
C16 C17 C18 C19
C20 C27 C28 C29 47uF
C30 C36
C26
8.2nF
L1
0.215uH
R1
1.91K
R2
4.22K
R3
4.22K
R4
127
R6
20
R9
39.2K
R8 R28 R10 R11
0
R44 R33 R34
C39
1uF
C66
10uF
R15 R32
4.22K
R30 R31
0
R18
49.9K
R19
7.5K
R17 R29
10K
RED
BLACK
IR3847
Description
Manufacturer
Part Number
1206, 25V, X5R, 10%
Murata
GRM31CR61E226KE15L
SMD Elecrolytic, Fsize, 25V,
20%
Panasonic
EEV-FK1E331P
0603, 25V, X7R, 10%
Murata
GRM188R71E104KA01D
2200pF,0603,50V,X7R
50V, 0603, NP0, 5%
Murata
Murata
GRM188R71H222KA01D
GRM1885C1H161JA01D
0805, 6.3V, X5R, 20%
TDK
C2012X5R0J476M
0603, 50V, X7R, 10%
0.215uH, DCR=0.29mohm
0603,1/10W,1%
0603,1/10W,1%
0603,1/10W,1%
0603,1/10W,1%
0603,1/10 W,1%
0603,1/10 W,1%
Murata
Cyntec
Panasonic
Panasonic
Panasonic
Panasonic
Vishay/Dale
Panasonic
GRM188R71H822KA01D
PCDC1008-R215EMO
ERJ-3EKF1911V
ERJ-3EKF4221V
ERJ-3EKF4221V
ERJ-3EKF1270V
CRCW060320R0FKEA
ERJ-3EKF3922V
0603,1/10 W,5%
Vishay/Dale
CRCW06030000Z0EA
0603, X5R, 25V, 20%
0603, X5R, 10V, 20%
0603,1/10 W,1%
1206,1/4 W, 5%
0603,1/10 W,1%
0603,1/10 W,1%
0603,1/10 W,1%
PLUG 40 POS DBL ROW
STR
SCREW TERMINAL
SCREW TERMINAL
IR3847 5mm X6mm
TDK
TDK
Panasonic
Yageo
Panasonic
Panasonic
Panasonic
C1608X5R1E105M
C1608X5R1A106M
ERJ-3EKF4221V
RC1206JR-070RL
ERJ-3EKF4992V
ERJ-3EKF7501V
ERJ-3EKF1002V
Omron Electronics Inc.
XG8W-4041-ND
Keystone Electronics
Keystone Electronics
International Rectifier
8199-2
8199-3
IR3847MPBF
6
IRDC3847-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow
Fig. 2: Start up at 25A Load
Ch1:Vin, Ch2:Vo, Ch3:PGood, Ch4:Enable
Fig. 4: Start up with 1.08V Pre Bias, 0A Load
Ch1:Enable, Ch2:Vout, Ch3:PGood
Fig. 6: Inductor node at 25A load
Ch2:LX
4/11/2013
Fig. 3: Start up at 25A Load
Ch1:Vin, Ch2:Vo, Ch3:PGood,Ch4:Vcc
Fig. 5: Output Voltage Ripple, 25A load
Ch1: Vout
Fig. 7: Short (Hiccup) Recovery
Ch2:Vout , Ch3:PGood, Ch4:Iout
7
IRDC3847-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=1.2V, Io=2.5A-12.5A, Fsw=600kHz, Room Temperature, No air flow
Fig. 8: Transient Response, 2.5A to 12.5A step (2.5A/us)
Ch2:Vout, Ch4:Iout(10A/V)
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IRDC3847-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=1.2V, Io=15A-25A, Fsw=600kHz, Room Temperature, No air flow
Fig. 9: Transient Response, 15A to 25A step (2.5A/us)
Ch2:Vout, Ch4:Iout(10A/V)
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IRDC3847-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow
Fig. 10: Bode Plot at 25A load: Fo = 108.0kHz; Phase Margin = 50.2º
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IRDC3847-P1V2
Efficiency [%]
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow
92
90
88
86
84
82
80
78
76
74
72
70
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Io [A]
Fig.11: Efficiency versus load current
5.0
4.5
Power Loss [W]
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Io [A]
Fig.12: Power loss versus load current
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IRDC3847-P1V2
THERMAL IMAGES
Vin=12.0V, Vo=1.2V, Io=0A-25A, Fsw=600kHz, Room Temperature, No air flow
Fig. 13: Thermal Image of the board at 25A load
Test point 1 is IR3847: 750C
Test point 2 is inductor: 61.50C
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IRDC3847-P1V2
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. 10/11
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