IRDC3846-P1V2 - International Rectifier

IRDC3846-P1V2
SupIRBuck
TM
USER GUIDE FOR IR3846 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 IR3846 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 (+ 13.2V Max)
• Vout = +1.2V @ 0-35A
• Fs= 400kHz
• L= 0.23uH
• Cin= 7x22uF (ceramic 1206) + 1x330uF* (electrolytic)
• Cout= 18x100uF (ceramic 0805)
* The 330uF input capacitor is placed for damping the parasitic inductance of bench power supply
wires. It is not required for the POL applications where input is delivered with power planes.
10/7/2013
Confidential
1
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
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(+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 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.
10/7/2013
Confidential
2
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
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
10/7/2013
Confidential
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This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
Agnd
1
Vcc-
1
Vcc+
1
VCC
1
Enable
C19
N/S
0 R3
PVin
C5
N/S
R16
6.98k
R9
60.4k
OCset
RT/Sy nc
Enable
BOOT
NC2
NC1
PVin
68pF
C12
R114
N/S
7
6
5
4
3
2
1
U1
Confidential
C14
N/S
C13
2200pF
0 R10
C75
22uF
R15
20
R18
0
NC3
Vref
Vp
PGD
Vin
VCC
C16
N/S
0 R116
R71
R70
PVin
Vin
L1
R110
10k
JUMPER 3
BODE2
C6
1uF
330uF
+ C81
0 R115
0
N/S R4
C8
10uF
C80
N/S
N/S
0 R118
N/S R117
17 Vref
18
19 PGD
20 Vin
SW
C79
N/S
C17
100pF
VCC
C78
N/S
21 VCC
22
23
24
BODE1
JUMPER 2
R19
N/S
S_Ctrl
SW
C77
22uF
NC4
C76
22uF
1
C15
N/S
Vout
Vp
R111
N/S
6
5
4
3
2
1
6
5
4
3
2
1
Vo_R_N
Vo_R_P
R113
N/S
R112
N/S
VDDQ
0.23uH
N/S R49
N/S R48
0 R47
0 R46
+ C125
N/S
+ C126
N/S
+ C127
N/S
+ C128
N/S
N/S
N/S
N/S
N/S
N/S
C122 C123 C124
+ C129
N/S
C119 C120 C121
100uF 100uF 100uF 100uF 100uF 100uF N/S
C109 C110 C111 C116 C117 C118
0.1uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF 100uF
C100 C101 C102 C103 C104 C105 C106 C107 C108 C113 C114 C115 C112
Vin-
Vin+
Fig. 1: Schematic of the IR3846 evaluation board
6.98k R13
R12
196 Ohm
C11
3.9nF
IR3846
0.1uF C10
BOOT
C74
22uF
26
NC5
C73
22uF
1
C72
22uF
8.06k R11
C71
22uF
RT/Sy nc
BOOT
6.98k R14
R17
6.98k
R101
7.5k
R100
49.9k
C70
0.1uF
FB
1
PVin
VCC
Vin
FB
Comp
10
Vsns
8
Vsns
9
FB
RSo
11
PGND
12
LGND
13
RS15
S_Ctrl
14
1
RS+
16
PG_PU
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1
Vin
0.1uF
C130
6
5
4
3
2
1
6
5
4
3
2
1
Vout-
Vout+
Vout
IRDC3846-P1V2
4
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
Bill of Materials
Item Qty Part Reference Value
Description
Manufacturer
Part Number
C71 C72 C73
1
7
C74 C75 C76
22uF 1206, 25V, X5R, 10%
Murata
GRM31CR61E226KE15L
C77
C6
1uF
0603, X5R, 25V, 20%
TDK
2
1
C1608X5R1E105M080AC
C8
10uF 0603, X5R, 10V, 20%
TDK
3
1
C1608X5R1A106M080AC
4
3 C10 C70 C100 0.1uF 0603, 25V, X7R, 10%
Murata
GRM188R71E104KA01D
5
1
C11
3900pF 0603, 50V, X7R, 10%
Murata
GRM188R71H392KA01D
6
1
C12
68pF
0603, 50V, NP0, 5%
Murata
GRM1885C1H680JA01D
7
1
C13
2200pF 0603, 50V, X7R, 10%
Murata
GRM188R71H222KA01D
8
1
C17
100pF 0603, 50V, NP0, 5%
Murata
GRM1885C1H101JA01D
SMD Elecrolytic, Fsize,
9
1
C81
330uF
Panasonic
EEV-FK1E331P
25V, 20%
45A Isat., 0.29m Ohm,
10 1
L1
0.23uH
Coiltronics
FP1107R1-R23-R
7.2x11.0x7.5mm
C101 C102 C103
C104 C105 C106
C107 C108 C109
11 18
100uF 0805, 4V, X5R, 20%
Murata
GRM21BR60G107M
C110 C111 C112
C113 C114 C115
C116 C117 C118
R3 R10 R18
12 6
0
0603,1/10W, Jumper
Vishay/Dale
CRCW06030000Z0EA
R115 R116 R118
13 1
R9
60.4k
0603,1/10W,1%
Panasonic
ERJ-3EKF6042V
14 1
R11
8.06k
0603,1/10W,1%
Panasonic
ERJ-3EKF8061V
15 1
R12
196
0603,1/10W,1%
Panasonic
ERJ-3EKF1960V
R13 R14 R16
16 4
6.98k
0603,1/10W,1%
Panasonic
ERJ-3EKF6981V
R17
17 1
R15
20
0603,1/10W,1%
Vishay/Dale
CRCW060320R0FKEA
18 2
R46 R47
0
1206,1/4W, Jumper
Yageo
RC1206JR-070RL
19 1
R71
0
0402, 1/16W, Jumper
Yageo
RC0402JR-070RL
20 1
R100
49.9k
0603,1/10 W,1%
Panasonic
ERJ-3EKF4992V
21 1
R101
7.5k
0603,1/10W,1%
Panasonic
ERJ-3EKF7501V
22 1
R110
10k
0603,1/10 W,1%
Panasonic
ERJ-3EKF1002V
International
23 1
U1
IR3846 IR3846 5mm X 7mm
IR3846MPBF
Rectifier
10/7/2013
Confidential
5
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow
Fig. 2: Start up at 35A load
Ch1:Vin, Ch2:Vout, Ch3:PGood, Ch4:Enable
Fig. 3: Start up at 35A load
Ch1:Vin, Ch2:Vout, Ch3:PGood, Ch4:Vcc
Fig. 4: Start up with 1.0V pre bias, 0A load
Ch2:Vout, Ch3:PGood, Ch4:Enable
Fig. 5: Output voltage ripple, 35A load
Ch2: Vout
Fig. 7: Short (Hiccup) recovery
Ch2:Vout, Ch3:PGood
Fig. 6: Inductor node at 35A load
Ch3:SW Node
10/7/2013
Confidential
6
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow
Fig. 8: Transient response, 0A to 10A Iout at 11.31A/us raising/ 10.34A/us falling slew rates.
Ch1:Vimonitor (20.45mV/A)*, Ch2:Vout
*Vimonitor is the voltage measured across a current sense resistor in series with the step load at
a 20.45mV/A ratio.
10/7/2013
Confidential
7
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow
Fig. 9: Transient response, 25A* to 35A Iout at 14.06A/us raising/ 10.01A/us falling slew rates.
Ch1:Vimonitor (20.45mV/A)**, Ch2:Vout
* An additional constant 25 A load is provided by the electronic load; the figures above show the 10A load step part.
** Vimonitor is the voltage measured across a current sense resistor in series with the step load at a 20.45mV/A ratio.
10/7/2013
Confidential
8
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow
60
200
150
40
20
50
0
TR2/°
TR1/dB
100
0
-50
-20
-100
-40
-60
-150
103
104
105
-200
f/Hz
TR1: Mag(Gain)
TR2: Unwrapped Phase(Gain)
Fig. 10: Bode Plot at 35A load: Fc = 89.37kHz; Phase Margin = 48.76º.
10/7/2013
Confidential
9
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow
Fig.11: Efficiency versus load current
Fig.12: Power loss versus load current
10/7/2013
Confidential
10
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL
IRDC3846-P1V2
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=1.2V, Iout=0A-35A, Fsw=400kHz, Room Temperature, No air flow
Fig. 13: Thermal Image of the board at 35A load
IR3846: 97.31 0C
Inductor: 75 .120C
Ambient: 28.29 0C
10/7/2013
Confidential
11
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3846. Based on the results
of the continuing evaluation, this board can evolve and change without notice
AL