Reference Design - IRDC3710-QFN

IRDC3710-QFN
SupIRBuck
TM
USER GUIDE FOR IRDC3710-QFN EVALUATION BOARD
DESCRIPTION
The IR3710M is a single phase sync-buck
PWM controller IC optimized for efficiency in
high performance portable electronics. The
switching modulator uses constant ON-time
control. Constant ON-time with diode
emulation provides the highest light load
efficiency required for all applications.
Key features offered by the IR3710M
include: programmable switching frequency,
soft start, forced continuous conduction
mode (FCCM) operation at light load and
over current protection.
Additional features include pre-bias startup,
very precise 0.5V reference, over/under voltage
fault protection, power good output, and enable
input with voltage monitoring capability. The
gate drive is designed to operate up to 7.5V to
enhance over all system efficiency.
This user guide contains the schematic and bill
of materials for the IRDC3710-QFN evaluation
board. The guide describes operation and use
of the evaluation board itself. Detailed
specifications and application information for
IR3710M is available in the IR3710M data
sheet.
BOARD FEATURES
• Vin = +12V Typical ( 8-19V input Voltage range. Pls. see note below)
• PVcc= +5.0V
• Vcc=+3.3V
• Vout = +1.1V @ 0- 20A
• Fs = 300kHz @ 20A
• L = 0.5uH
• Cin= 2x10uF (ceramic 1210) + 1x330uF (electrolytic)
• Cout= 2x10uF (ceramic 1206) + 3x330uF(SP Cap)
Note: At low input line an additional 10uF ceramic capacitor is recommended at
input to handle higher ripple current)
1
IRDC3710-QFN
CONNECTIONS and OPERATING INSTRUCTIONS
A regulated +12V input supply should be connected to VIN+ and Vin-. A maximum 20A 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.
IRDC3710-QFN has three input connectors, one for gate drive supply (PVcc),one for biasing (Vcc) and the
third one as input voltage (Vin). Separate supplies should be applied to these inputs. PVcc input should be
a well regulated 4.5V-5.5V supply and it would be connected to +5V and GROUND and Vcc input should be
a well regulated 3.0V-3.6V supply and it would be connected to +3.3V and GROUND. An external signal
can be provided as Enable signal to turn on or turn off the converter if desired. This signal is not required to
power up the Evaluation board as EN pin is connected to a voltage divider from Vin. The absolute maximum
voltage of Enable signal is +3.9V.
The evaluation board is configured for use with 2x10uF (ceramic 1206) + 3x330uF (SP) capacitors.
However, the design can be modified for an all ceramic output cap configuration by adding the inductor
DCR sensing circuit as show in the schematic.
Table 1: Connections
Connection
Signal Name
VIN+
VIN (+12V)
VIN-
Ground of VIN
+5V
PVcc input (+5.0V)
+3.3V
Vcc input (+3.3V)
GROUND
Ground for PVcc and Vcc input
VOUT+
Vout (+1.1V)
VOUT+
Ground of Vout
Enable
Enable input
LAYOUT
The PCB is a 4-layer board. All layers are 2 Oz. copper. The IR3710M and other components are mounted
on the top and bottom side of the board.
Power supply decoupling capacitors, the Bootstrap capacitor and feedback components are located close
to IR3710M. The feedback resistors are connected to the output voltage at the point of regulation and are
located close to IR3710M. To improve efficiency, the circuit board is designed to minimize the length of the
on-board power ground current path.
2
IRDC3710-QFN
Vin = +12V
Vin-
Enable
V out-
PGood
Vcc = +3.3V
V = +1.1V
out
PVcc = +5.0V
GROUND
Figure 1: Connection diagram of IRDC3710-QFN evaluation
board
3
IRDC3710-QFN
Figure 2: PCB layout, top layer
Figure 3: PCB layout, bottom layer
4
IRDC3710-QFN
Figure 4: Board layout, mid-layer I
Figure 5: Board layout, mid-layer II
5
Figure 6: Schematic of the IRDC3710-QFN Evaluation board
IRDC3710-QFN
6
IRDC3710-QFN
Bill of Materials
Item
Number
Quanti
ty
Part
Reference
1
4
C1 C2 C3
C4
0.1uF
2
1
C5
2.2uF
3
1
C7
4
2
5
Value
Description
Manufacturer1
Manufacturer Part Number
Murata Electronics
North America
GRM188R61E105KA12D
Ceramic, 6.3V, 0603, X7R, 10%
Murata Electronics
North America
GRM185R60J225KE26D
1.0uF
Ceramic, 25V, 0805, X5R, 10%
Taiyo Yuden
TMK212BJ105KG-T
C8 C9
10uF
Ceramic,25V,1210,X5R,10%
Taiyo-Yuden
TMK325BJ106MN-T
1
C10
330uF
SMD Electrolytic, 25V,
F-size,20%
Panasonic
EEE-FK1E331P
6
1
C12
1.0uF
Ceramic,25V,0603,X5R,10%
Murata Electronics
North America
GRM188R61E105KA12D
7
3
C13 C14
C15
330uF
SP-Cap,Dcase,4V,20%
Panasonic
EEFUE0G331XE
8
2
C16 C17
10uF
Ceramic,6.3V,1206,X5R,20%
Murata Electronics
North America
GRM21BCB0G106ME19F
Ceramic,25V,0603,X7R,10%
C11,C18,C2
0,C22
N/S
C21,23,C24,
C25
N/S
9
1
C19
22000pF
Ceramic,50V,0603,X7R,10%
TDK Corporation
C1608X7R1H223K
10
1
D1
BAT54S
Diode,40V,BAT54S,SOT-23
Diodes, Inc.
BAT54S
11
1
D2
BAS316
Diode 75V , 0.25A, SOD323
NXP
BAS316
12
1
L1
500nH
Toko
FDUE1245-R50M
13
1
Q1
IRFH7921PbF
Mosfet 30V 8.5mOhm PQFN
International
Rectifier
IRFH7921PbF
14
1
Q2
IRFH7932PbF
Mosfet 30V 3.3mOhm PQFN
International
Rectifier
IRFH7932PbF
15
4
R13 R17
R18
10K
Thick-film,0603,1/10W,1%
Vishay/Dale
CRCW060310K0FKEA
R4
48.7K
Thick-film,0603,1/10W,1%
Rohm
MCR03EZPFX4872
SMT-Inductor,
0.8mOhm,12.1x13.4mm,20%
16
1
R5
180K
Thick-film,0603,1/10W,1%
Rohm
MCR03EZPFX1803
17
1
R7
7..5K
Thick-film,0603,1/10 W,1%
Rohm
MCR03EZPFX7501
18
1
R12
1.96K
Thick-film,0603,1/10W,1%
Rohm
MCR03EZPFX1961
19
3
R14 R19
0
Thick-film,0603,1/10 W,5%
Vishay/Dale
CRCW06030000Z0EA
R9,R11,R16
N/S
20
1
R15
1.65K
Thick-film,0603,1/10W,1%
Panasonic - ECG
ERJ-3EKF1651V
21
1
SW1
Switch, 2-Pos.
Switch, DIP, 2-Pos., SPDT
Copal Electronics
Inc
CJS-1200TB
22
1
U1
IR3710MPbF
IR3710,
Controller,PQFN,3x3mm
International
Rectifier
IR3710MPbF
7
IRDC3710-QFN
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V,Vo=1.1V, Io=0- 20A, , Room Temperature, No Air Flow
Ch1-Phase Voltage(10V/Div)
Ch3-CPO(2V/Div)
Ch2-Vout(50mV/div)
Time: 10uS/Div)
Figure 7: Charge Pump Off at Iout = 0.5A
Ch1-Phase Voltage (10V/Div)
Ch2-Vout(50mV/Div)
Figure 9: Load Step (5A to 15A) Transient at 12Vin
Ch1-Phase Voltage(10V/Div)
Ch3-CPO(2V/Div)
Ch2-Vout(50mV/div)
Time: 2uS/Div)
Figure 8: Charge Pump On at Iout =5A
Ch1-Phase Voltage (10V/Div)
Ch2-Vout(50mV/Div)
Figure 10: Load Step (5A to 15A) Transient at 19Vin
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IRDC3710-QFN
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V,Vo=1.1V, Io=0- 20A, Room Temperature, No Air Flow
Ch1-Phase Voltage (10V/Div)
Ch2-Vout(50mV/Div)
Figure 11: DCM/CCM transition
from 1.0A to 5A at 12Vin
Ch1-Phase Voltage (10V/Div)
Ch3-EN(2V/Div)
Ch2-Vout(500mV/Div)
Ch4-PGood(2V/Div)
Figure 13: Startup/Shutdown 12Vin at 0.5A
Ch1-Phase Voltage (10V/Div)
Ch2-Vout(50mV/Div)
Figure 12: DCM/CCM transition
from 1.0A to 5A at 19Vin
Ch1-Phase Voltage (10V/Div)
Ch3-EN(2V/Div)
Ch2-Vout(500mV/Div)
Ch4-PGood(2V/Div)
Figure 14: Startup/Shutdown 12Vin at 5.0A
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IRDC3710-QFN
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V, Vo=1.1V, Io=0- 20A, , Room Temperature, No Air Flow
92
5
90
4.5
4
88
Efficiency(%)
3
84
2.5
82
2
80
Power Loss(W)
3.5
86
1.5
78
1
76
0.5
74
0
0
4
8
12
16
20
Iout(A)
Eff 12V Input CP ON
Power Loss 12V Input CP ON
Eff 12V input CP OFF
Power Loss 12V Input CP OFF
Figure 15: Typical Efficiency and Power Loss at Vin-12V
5
90
4.5
4
3.5
3
70
2.5
2
60
Power Loss(W)
Efficiency(%)
80
1.5
1
50
0.5
40
0
0
4
8
12
16
Eff 19V Input CP ON
Iout(A)Eff 8V Input CP ON
Power Loss 19V Input CP ON
Power Loss 8V Input CP ON
20
Figure 16: Typical Efficiency and Power Loss at Vin=8V and 19V
10
IRDC3710-QFN
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V, Vo=1.1V, Io=0- 20A, , Room Temperature, No Air Flow
1.1060
1.1040
1.1020
Vout(V)
1.1000
1.0980
1.0960
1.0940
1.0920
12V Input
8V Input
19V Input
1.0900
0
4
8
12
16
20
Iout(A)
Figure 17: Typical Output Voltage Regulation
Q1: 73.2°C, Q2:83.2°C, IC-64.2°C,Inductor: 53.5°C, PCB: 53.3°C
Figure 18:Thermal Image @12Vin, 20A, With CP On
11
IRDC3710-QFN
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V, Vo=1.1V, Io=0- 20A, , Room Temperature, No Air Flow
Q1: 82.5°C, Q2:94.8°C, IC-69.7°C,Inductor: 58.1°C, PCB: 56.4°C
Figure 19: Thermal Image @19Vin, 20A, With CP On
Q1:83.2°C,Q2:91.2°C, IC-68.7°C, Inductor: 57.1°C, PCB: 55.9°C
Figure 20: Thermal Image @12Vin, 20A, With CP Off
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IRDC3710-QFN
PACKAGE INFORMATION
13