IRDC3820A
Rev 0.0
01/07/2008 1
USER GUIDE FOR IR3820A EVALUATION BOARD
DESCRIPTION
The IR3820A is a synchronous buck
converter, providing a compact, high
performance and flexible solution in a small
5mmx6mm Power QFN package.
Key features offered by the IR3820A include
programmable soft-start ramp, precision
0.6V reference voltage, programmable
Power Good,thermal protection, fixed
300kHz switching frequency requiring no
external component, input under-voltage
lockout for proper start-up, and pre-bias
start-up.
An 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 IR3820A evaluation board.
The guide describes operation and use of the
evaluation board itself. Detailed application
information for the IR3820A is available in the
IR3820A data sheet.
BOARD FEATURES
•Vin = +12V (13.2V Max)
•Vout = +1.8V @ 0- 14A
•L= 1.0uH
•Cin= 3x10uF (ceramic 1206) + 1x330uF (Electrolytic)
•Cout= 6x22uF (ceramic 0805)
SupIRBuckTM
IRDC3820A
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Table I. Connections
Ground for Optional Vcc inputVcc-
Optional Vcc inputVcc+
Vout (+1.8V)VOUT+
Power Good SignalP_Good
Ground of Vout
VOUT-
Ground of Vin
VIN-
Vin (+12V)VIN+
Signal NameConnection
CONNECTIONS and OPERATING INSTRUCTIONS
A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum 14A 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.
IR3820A has two input supplies, one for biasing (Vcc) and the other as input voltage (Vin). These inputs are
connected on the board with a zero ohm resistor (R15). Separate supplies can be applied to these inputs.
Vcc input cannot be connected unless R15 is removed. Vcc input should be a well regulated 5V-12V supply
and it would be connected to Vcc+ and Vcc-.
LAYOUT
The PCB is a 4-layer board. All of layers are 2 Oz. copper. The SupIRBuck and all of the passive
components are mounted on the top side of the board.
Power supply decoupling capacitors, the charge-pump capacitor and feedback components are located
close to the IR3820A. The feedback resistors are connected to the output voltage at the point of
regulation and are located close to the SupIRBuck.
The input and output energy storage capacitors and the power inductor are located on top side of the
board, these are connected to IR3820A through vias. To improve efficiency, the circuit board is
designed to minimize the length of the on-board power ground current path.
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Fig. 2: Board layout, top overlay
Fig. 3: Board layout, bottom overlay (rear view)
IRDC3820A
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Fig. 1: Connection diagram of the IR3820A evaluation board
Vin= +12v GROUND
(Optional External)
VCC+
GROUND
PGood
VOUT = +1.8v
GROUND
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Fig. 4: Board layout, mid-layer I
Fig. 5: Board layout, mid-layer II
Single point
connection
between AGND
and PGND.
AGND
Plain PGND
Plain
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Fig. 6: Schematic of the IR3820A evaluation board
Single point of connection between Power
Ground and Signal ( “analog” ) Ground
Vout-
1
+
C21
N/S
+
C22
N/S
Vin
C14
0.1uF
Vcc-
1
C10
0.22uF
PGND
1
C12
0.1uF
C24
390pF
C23
Open
D1
BAT54S
12
3
C26
2200pF
C13
1uF
Vout
Vcc+
1
C2
10uF
C5
N/S
R9
0
R1
15.8k
R10
Open
C3
10uF
R3
40.2K
R4
2.61K
R2
80.6k
C4
10uF
C15
22uF
R6
20
C16
22uF
C25
0.1uF
C17
22uF
R12
10.7K
J1
SS
C9
Open
C18
22uF
C19
22uF
C20
22uF
A
1
B
1
D2
Open
12
R18
Open
+
C1
330uF
L1
1.0uH
VCC
C8
180pF
C7
0.1uF
R15 0
Agnd
1
Vin+
1
Vin-
1
Vout+
1
Vout-
1
U1
IR3820A
Vc 14
Hg 13
AGnd3
15
AGnd2
5
SW 11
PGood
9
COMP
3
OCset
7PGnd 10
SS
6
Vsns
1
FB
2
AGnd1
4
Vcc
8
Vin 12
R17
10K
PGood
1
C11 39pF
C6
N/S
VCC
VCC
Vin+
1
R16 3.09k
Vin-
1
R14
10k
Vout+
1
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Item Quantity Designator Value Description Size Manufacturer Mfr. Part Number
1 1 C1 330uF SMD Electrolytic, 25V, 20% SMD Panasonic EEV-FK1E331P
2 3 C2 C3 C4 10uF Ceramic, 16V, X7R, 10% 1206 Panasonic ECJ-3YX1C106K
34 C7 C12 C14
C25 0.1uF Ceramic, 50V, X7R, 10% 0603 Panasonic ECJ-1VB1H104K
4 1 C10 0.22uF Ceramic, 10V, X5R, 10% 0603 Panasonic ECJ-1VB1A224K
5 1 C8 180pF Ceramic, 50V, NPO, 5% 0603 Murata GRM1885C1H181JA01
6 1 C11 39pF Ceramic, 50V, NPO, 5% 0603 Murata GRM1885C1H390JA01
7 1 C13 1uF Ceramic, 16V, X5R, 10% 0603 Panasonic ECJ-1VB1C105K
86 C15 C16 C17
C18 C19 C20 22uF Ceramic, 6.3V, X5R, 20% 805 Panasonic ECJ-2FB0J226M
9 1 C24 390pF Ceramic, 50V, NPO, 5% 0603 Murata GRM1885C1H391JA01
10 1 C26 2200pF Ceramic, 50V, NPO, 5% 0603 Murata GRM1885C1H222JA01
11 1 D1 BAT54S Diode Schottky ,40V, 200mA SOT-23 Fairchild BAT54S
12 1 L1 1.0uH SMT Inductor, 2.3mOhm,
20%
11.5x
10mm Delta MPL105-1R0
13 1 R1 15.8K Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW060315K8FKEA
14 1 R3 40.2K Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW060340K2FKEA
15 1 R2 80.6K Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW060380K6FKEA
16 1 R4 2.61K Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW06032K61FKEA
17 1 R6 20 Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW060320R0FKEA
18 2 R9 R15 0 Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW06030000Z0EA
19 1 R12 10.7K Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW060310K7FKEA
20 2 R14, R17 10K Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW060310K0FKEA
21 1 R16 3.09K Thick film, 1/10W, 1% 0603 Vishey/Dale CRCW06033K09FKEA
22 1 U1 IR3820A 300kHz, 14A, SupIRBuck
Module 5x6mm International
Rectifier IR3820A
23 2 - - Banana Jack, Insulated
Solder Terminal, Black -Johnson
Components 105-0853-001
24 1 - - Banana Jack- Insulated
Solder Terminal, Red -Johnson
Components 105-0852-001
25 1 - - Banana Jack- Insulated
Solder Terminal, Green -Johnson
Components 105-0854-001
Bill of Materials
IRDC3820A
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Fig. 12: Shorted Hiccup Condition Recovery
Ch2:VSS, Ch3:Vout
TYPICAL OPERATING WAVEFORMS
Vin=Vcc=12.0V, Vo=1.8V, Io=0- 14A, Room Temperature, No Air Flow
Fig. 10: Output Voltage Ripple, 14A load
Ch3: Vout ,Ch4: Iout
Fig.7: Start up into 14A Load
Ch1:Vin, Ch2:VSS, Ch3:Vout, Ch4:Iout
Fig. 9: Pre-Bias Start up, 0A Load
Ch1:Vin, Ch2:VSS, Ch3:Vout
Fig. 11: Inductor node voltage at 14A load
Ch1:LX, Ch4:Iout
Fig. 8: Start up into 14A Load,
Ch1:Vin, Ch2:VSS, Ch3:Vout,Ch4:VPGood
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TYPIVcc=CAL OPERATING WAVEFORMS
Vin=12V, Vo=1.8V, Io=7A- 14A, Room Temperature, No Air Flow
Fig. 13: Transient Response, 7A to 14A step
Ch1:Vout, Ch4:Iout
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TYPICAL OPERATING WAVEFORMS
Vin=Vcc=12V, Vo=1.8V, Io=14A, Room Temperature, No Air Flow
Fig. 14: Bode Plot at 14A load shows a bandwidth of 52.4kHz and phase margin of 54.2 degrees
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0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 2 4 6 8 101214
Load Current (A)
Power Loss (W)
70
72
74
76
78
80
82
84
86
88
90
1234567891011121314
Load Current (A)
Efficiency (%)
TYPICAL OPERATING WAVEFORMS
Vin=Vcc=12V, Vo=1.8V, Io=0-14A, Room Temperature, No Air Flow
Fig. 15: Efficiency versus load current
Fig. 16: Power Loss versus load current
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THERMAL IMAGES
Vin=Vcc=12V, Vo=1.8V, Io=14A, Room Temperature, 200 LFM Air Flow
Fig. 17: Thermal Image at 14A load, Test point 1 is the IR3820A
IRDC3820A
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PCB Metal and Components Placement
The lead lands (the 11 IC pins) width should be equal to the nominal part lead width. The minimum
lead to lead spacing should be ≥0.2mm to minimize shorting.
Lead land length should be equal to the maximum part lead length + 0.3 mm outboard extension. The
outboard extension ensures a large and inspectable toe fillet.
The pad lands (the 4 big pads other than the 11 IC pins) length and width should be equal to
maximum part pad length and width. However, the minimum metal to metal spacing should be no less
than 0.17mm for 2 oz. Copper; no less than 0.1mm for 1 oz. Copper and no less than 0.23mm for 3 oz.
Copper.
IRDC3820A
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01/07/2008
Solder Resist
It is recommended that the lead lands are Non Solder Mask Defined (NSMD). The solder resist
should be pulled away from the metal lead lands by a minimum of 0.025mm to ensure NSMD
pads.
The land pad should be Solder Mask Defined (SMD), with a minimum overlap of the solder resist
onto the copper of 0.05mm to accommodate solder resist mis-alignment.
Ensure that the solder resist in between the lead lands and the pad land is ≥0.15mm due to the
high aspect ratio of the solder resist strip separating the lead lands from the pad land.
IRDC3820A
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Stencil Design
• The Stencil apertures for the lead lands should be approximately 80% of the area of the
lead lads. Reducing the amount of solder deposited will minimize the occurrences of lead
shorts. If too much solder is deposited on the center pad the part will float and the lead
lands will be open.
• The maximum length and width of the land pad stencil aperture should be equal to the
solder resist opening minus an annular 0.2mm pull back to decrease the incidence of
shorting the center land to the lead lands when the part is pushed into the solder paste.
IRDC3820A
Rev 0.0
01/07/2008
IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105
TAC Fax: (310) 252-7903
This product has been designed and qualified for the Consumer market.
Visit us at www.irf.com for sales contact information
Data and specifications subject to change without notice. 11/07
