User Guide - International Rectifier

IRDC3895-P3V3
SupIRBuck
TM
USER GUIDE FOR IR3895 EVALUATION BOARD
3.3Vout
DESCRIPTION
The IR3895 is a synchronous buck
converter, providing a compact, high
performance and flexible solution in a small
5mm X 6 mm Power QFN package.
Key features offered by the IR3895 include
internal Digital Soft Start/Soft Stop, precision
0.5Vreference 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, smart internal LDO and pre-bias
start-up.
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 IR3895 evaluation board.
The guide describes operation and use of the
evaluation board itself. Detailed application
information for IR3895 is available in the
IR3895 data sheet.
BOARD FEATURES
• Vin = +12V (+ 13.2V Max)
• Vout = +3.3V @ 0- 16A
• Fs= 400kHz
• L= 1.0uH
• Cin= 5x10uF (ceramic 0805) + 1X0.1uF (ceramic 0402) + 1X330uF (electrolytic, 25V)
• Cout= 6x47uF (ceramic 0805) + 1X0.1uF (ceramic 0402)
9/25/2012
1
IRDC3895-P3V3
CONNECTIONS AND OPERATING INSTRUCTIONS
A well regulated +12V input supply should be connected to VIN+ and VIN-. A maximum of 16A load should
be connected to VOUT+ and VOUT-. The input and output connections of the board are listed in Table I.
IR3895 has only one input supply and internal LDO generates Vcc from Vin. If operation with external Vcc
is required, then R15 can be removed and external Vcc can be applied between Vcc+ and Vcc- pins. Vin pin
and Vcc/LDOout pins should be shorted together for external Vcc operation (use zero ohm resistor for R29).
The output can track voltage at the Vp pin. For this purpose, Vref pin is to be connected to ground (use zero
ohm resistor for R21). The value of R14 and R28 can be selected to provide the desired tracking ratio
between output voltage and the tracking input.
Table I. Connections
Connection
Signal Name
VIN+
Vin (+12V)
VIN-
Ground of Vin
Vout+
Vout(+3.3V)
Vout-
Ground for Vout
Vcc+
Vcc/ LDO_out Pin
Vcc-
Ground for Vcc input
Enable
Enable
PGood
Power Good Signal
Gnd
Analog ground
LAYOUT
The PCB is a 4-layer board (2.23”x2”) using FR4 material. All layers use 2 Oz. copper. The PCB
thickness is 0.062”. The IR3895 and other major power components are mounted on the top side of the
board.
Power supply decoupling capacitors, the bootstrap capacitor and feedback components are located
close to IR3895. The feedback resistors are connected to the output at the point of regulation and are
located close to the SupIRBuck IC. To improve efficiency, the circuit board is designed to minimize the
length of the on-board power ground current path.
9/25/2012
2
IRDC3895-P3V3
Vin
Gnd
Gnd
Vout
Enable
Top View
VDDQ
Vref
Sync
PGood
AGnd
S_Ctrl Vsns Vcc+ Vcc-
Bottom View
Fig. 1: Connection Diagram of IR3895/94 Evaluation Boards
9/25/2012
3
IRDC3895-P3V3
Fig. 2: Board Layout-Top Layer
Single point connection between
Analog Gnd and PGnd
Fig. 3: Board Layout-Bottom Layer
9/25/2012
4
IRDC3895-P3V3
Fig. 4: Board Layout-Mid Layer 1
Fig. 5: Board Layout-Mid Layer 2
9/25/2012
5
PGood
VCC
N/A
C10
R17
49.9K
Vcc+
Vcc-
N/S
R28
R14
0
1
1
1
1
VDDQ
2k
R1
10nF
C26
SYNC
60.4k
R9
220pF
C12
1nF
S_Ctrl
5
4
3
1
0
n/a
C37
Enable
1
C32
1.0uF
49.9K
R18
IR3895
R7
0 (N/S)
R3
715
100
R4
PGnd
SW
PVin
U1
N/S
R29
SW
VCC
R2
3300pF
C8
PGND
4.02k
11
12
C7
0.1uF
13
R10
0
R15
0
A
0.1uF
C24
Vsns
C25
n/a
R6
20
C6
B
R11
4.02k
R12
715
L1
1.0uH
R50
0
C4
10uF
C3
C27 C20
n/a 47uF
C19
47uF
C18
47uF
+ C36
N/S
+ C35
N/S
47uF, 0805, 6.3V, X5R, 20%
C28
n/a
C16
47uF
C2
10uF
C17
47uF
10uF
C1 +
1
1
1
1
1
1
1
1
C15
C14
47uF
0.1uF
Vout
330uF/25V
IR3895 5mmx6mm Power QFN package, Max Io=16A
C34 C33 C30
n/a n/a n/a
C29
n/a
C5
10uF
Input ceramic: 1206
10uF
Cyntec Inductor( PIMC104T-1R0MN)
C9
n/a
Fig. 6: Schematic of the IR3895 evaluation board
2.2uF
C23
VCC
S_Ctrl
Vp
Rt_Sy nc
AGnd
COMP
FB
R13
6
16
7.5k
R19
2
1
Agnd Agnd Agnd Agnd Agnd Agnd
1
Agnd
1
1
C11
1
7
VR EF
9
PG ood
R21
N/S
1
V s ns
8
15
E n a b le
V c c /LD O _O U T
10
V in
14
Boot
GND
17
1
1
1
VREF
1
1
1
1
1
9/25/2012
1
Vin
Vout-
Vout-
Vout+
Vout+
Vin-
Vin-
Vin+
Vin+
IRDC3895-P3V3
6
IRDC3895-P3V3
Bill of Materials
Item Qty
330uF
Description
SMD Electrolytic F size 25V 20%
Manufactur
er
Panasonic
EEV-FK1E331P
Part Reference
Value
Part Number
1
1
C1
2
5
C2 C3 C4 C5 C6
10uF
1206, 25V, X5R, 20%
TDK
C3216X5R1E106M
3
3
C7 C14 C24
0.1uF
TDK
C1608X7R1E104K
4
1
C12
1nF
603, 25V, X7R, 10%
0603, 25V, COG, 5%
Murata
GRM1885C1E102JA01D
5
1
C8
3300pF
6
1
C11
220pF
0603,50V,X7R,10%
0603, 50V, COG, 5%
Murata
Murata
GRM188R71H332KA01D
GRM1885C1H221JA01D
7
6
C15 C16 C17 C18 C19 C20
47uF
0805, 6.3V, X5R, 20%
Murata
GRM21BR60J476ME15
8
1
C23
2.2uF
0603, 16V, X5R, 20%
TDK
C1608X5R1C225M
Murata
GRM188R71E103KA01J
Murata
GRM188R61E105KA12D
9
1
C26
10nF
0603, 25V, X7R, 10%
10
1
C32
1.0uF
0603, 25V, X5R, 10%
11
1
L1
1.0uH
12
1
R1
2k
13
2
R2 R11
4.02k
SMD 10.3x11.5x4.0mm,3.0mΩ, Isat. 36A
Cyntec
Thick Film, 0603,1/10W,1%
Panasonic
Thick Film, 0603,1/10W,1%
Panasonic
PIMC104T-1R0MN
ERJ-3EKF2001V
ERJ-3EKF4021V
14
2
R3 R12
715
Thick Film, 0603,1/10W,1%
15
1
R4
100
Thick Film, 0603,1/10W,1%
Panasonic
ERJ-3EKF1000V
16
1
R6
20
Thick Film, 0603,1/10W,1%
Panasonic
ERJ-3EKF20R0V
Yageo
311-715HRCT-ND
17
1
R9
60.4k
Thick Film, 0603,1/10W,1%
Yageo
311-60.4KHCT-ND
18
5
R10 R13 R14 R15 R50
0
Thick Film, 0603,1/10W
Panasonic
ERJ-3GEY0R00V
19
2
R17 R18
49.9k
Thick Film, 0603,1/10W,1%
Panasonic
ERJ-3EKF4992V
Panasonic
ERJ-3EKF7501V
IR
IR3895MTR1PBF
20
1
R19
7.5k
Thick Film, 0603,1/10W,1%
21
1
U1
IR3895
PQFN 5x6mm
9/25/2012
7
IRDC3895-P3V3
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=3.3V, Iout=0-16A, Room Temperature
Fig. 7: Bode Plot at 16A load shows a bandwidth of 72.36kHz and phase margin of 65.29º.
9/25/2012
8
IRDC3895-P3V3
TYPICAL OPERATING WAVEFORMS
Vin=12.0V, Vout=3.3V, Iout=0-16A, Room Temperature, no air flow
Fig.8: Efficiency versus load current
Fig.9: Power loss versus load current
9/25/2012
9
IRDC3895-P3V3
PACKAGE INFORMATION
DIM
A
A1
b
b1
c
D
E
e
e1
e2
MILIMITERS
MIN
MAX
0.800 1.000
0.000 0.050
0.375 0.475
0.250 0.350
0.203 REF.
5.000 BASIC
6.000 BASIC
1.033 BASIC
0.650 BASIC
0.852 BASIC
INCHES
MIN
MAX
0.0315 0.0394
0.0000 0.0020
0.1477 0.1871
0.0098 0.1379
0.008 REF.
1.969 BASIC
2.362 BASIC
0.0407 BASIC
0.0256 BASIC
0.0335 BASIC
DIM
L
M
N
O
P
Q
R
S
t1, t2, t3
t4
t5
MILIMITERS
MIN
MAX
0.350 0.450
2.441 2.541
0.703 0.803
2.079 2.179
3.242 3.342
1.265 1.365
2.644 2.744
1.500 1.600
0.401 BASIC
1.153 BASIC
0.727 BASIC
INCHES
MIN
MAX
0.0138 0.0177
0.0961 0.1000
0.0277 0.0316
0.0819 0.0858
0.1276 0.1316
0.0498 0.0537
0.1041 0.1080
0.0591 0.0630
0.016 BACIS
0.045 BASIC
0.0286 BASIC
Figure 10: Package Dimensions
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 Industrial market
Visit us at www.irf.com for sales contact information
Data and specifications subject to change without notice. 12/11
9/25/2012
10