Reference Design - IRDC3710-DF

IRDC3710-DF
SupIRBuck
TM
USER GUIDE FOR IRDC3710-DF EVALUATION BOARD
DESCRIPTION
The IR3710M is 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-DF 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. See note below)
• PVcc= +5.0V
• Vcc=+3.3V
• Vout = +1.1V @ 0- 24A
• Fs = 300kHz @ 24A
• L = 0.5uH
• Cin= 2x10uF (ceramic 1210) + 1x330uF (electrolytic)
• Cout= 2x10uF (ceramic 1206) + 2x330uF(SP Cap)
Note: At low input line an additional 10uF ceramic capacitor is recommended at
input to handle higher ripple current)
1
IRDC3710-DF
CONNECTIONS and OPERATING INSTRUCTIONS
A regulated +12V input supply should be connected to VIN+ and Vin-. A maximum 24A 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-DF 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 PGND and Vcc input should be a
well regulated 3.0V-3.6V supply and it would be connected to +3.3V and AGND. 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) + 2x330uF (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)
PGND
Ground for PVcc input
AGND
Ground for 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-DF
Vin = +12V
Vin-
V out-
Enable
Vcc = +3.3V
Vout = +1.1V
GROUND
PVcc = +5.0V
GROUND
Figure 1: Connection diagram of IRDC3710-DF evaluation
board
3
IRDC3710-DF
Figure 2: PCB layout, top layer
Figure 3: PCB layout, bottom layer
4
IRDC3710-DF
Figure 4: Board layout, mid-layer I
Figure 5: Board layout, mid-layer II
5
Figure 6: Schematic of the IRDC3710-DF Evaluation board
IRDC3710-DF
6
IRDC3710-DF
Bill of Materials
1
4
C1,C2,C3,C4
0.1uF
Ceramic,25V,0603,X7R,10%
2
1
C5
2.2uF
Ceramic, 6.3V, 0603, X7R, 10%
3
1
C7
1.0uF
Ceramic, 25V, 0805, X5R, 10%
4
2
C8,C9
10uF
Ceramic,25V,1210,X5R,10%
5
1
C10
330uF
SMD Elecrolytic, 25V,F-size,20%
6
5
C11,C15C18,C20,C22
7
1
C12
1.0uF
Ceramic,25V,0603,X5R,10%
8
2
C13,C14
330uF
SP-Cap,Dcase,4V,20%
9
2
C16,C17
10uF
Ceramic,6.3V,1206,X5R,20%
10
1
C19
22000pF
Ceramic,50V,0603,X7R,10%
11
4
C21,C23,C24,C25
12
1
D1
BAT54S
Dual Diode,40V,BAT54S,SOT-23
13
1
D2
BAS316
Phillips 30V , 0.25A
14
1
L1
500nH
15
1
Q1
IRF6720S2TRPBF
IRF6720 30V
16
1
Q2
IRF6729MTRPBF
IRF6729 30V
17
1
R4
48.7K
Thick-film,0603,1/10W,1%
18
1
R5
180K
Thick-film,0603,1/10W,1%
19
1
R7
4.75k
Thick-film,0603,1/10 W,1%
20
3
R9,R11,R16
21
1
R12
22
3
R13,R17,R18
23
1
24
N/S
N/S
N/S
No Stuff
No Stuff
SMT-Inductor,0.8mOhms,Toko FDUE1245-R50M
No Stuff
1.96K
Thick-film,0603,1/10W,1%
10K
Thick-film,0603,1/10W,1%
R14
0
Thick-film,0603,1/10 W,5%
1
R15
1.65K
Thick-film,0603,1/10W,1%
25
1
SW1
Switch, 2-Pos.
Switch, DIP, 2-Pos., SPDT
31
1
U1
IR3710MMPbF
IR3710M, Controller,PQFN,3x3mm
7
IRDC3710-DF
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V,Vo=1.1V, Io=0- 24A, , 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-DF
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V,Vo=1.1V, Io=0- 24A, 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 1.0A
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-DF
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V, Vo=1.1V, Io=0- 24A, , Room Temperature, No Air Flow
95
6
90
5
4
80
3
75
2
Power Los(w)
Efficiency(%)
85
70
1
65
60
0
0
4
8
12
16
20
24
Iout(A)
Eff 12V Input CP ON
Power Loss 12V Input with CP
Eff 12V Input No CP
Power Loss 12V input No CP
Figure 15: Typical Efficiency and Power Loss at Vin-12V
5
95
90
4
3
80
75
2
Power Loss(W)
Efficiency(%)
85
70
1
65
60
0
0
4
8
12
16
20
24
Iout(A)
19V Input CP ON
Power Loss 8V Input
8V Input CP ON
Power Loss 19V Input
Figure 16: Typical Efficiency and Power Loss at Vin=8V and 19V
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IRDC3710-DF
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V, Vo=1.1V, Io=0- 24A, , Room Temperature, No Air Flow
1.105
1.103
1.101
Vout(V)
1.099
1.097
1.095
1.093
1.091
1.089
12V input
1.087
8V Input
19V Input
16
20
1.085
0
4
8
12
24
Iout(A)
Figure 17: Typical Output Voltage Regulation
Q1: 73.0°C, Q2:77.3°C, Inductor: 51.6°C, PCB: 52.8°C
Figure 18:Thermal Image @12Vin, 24A, With CP On
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IRDC3710-DF
TYPICAL OPERATING WAVEFORMS
Vin=12V, PVcc=5.0V, Vcc=3.3V, Vo=1.1V, Io=0- 24A, , Room Temperature, No Air Flow
Q1: 77.7°C, Q2:82.4°C,Inductor: 53.3°C, PCB: 54.1°C
Figure 19: Thermal Image @19Vin, 24A, With CP On
Q1:81°C,Q2:83.6°C, Inductor: 53.1°C, PCB: 53.6°C
Figure 20: Thermal Image @12Vin, 24A, With CP Off
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IRDC3710-DF
PACKAGE INFORMATION
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