an1822

Application Note 1822
ISL6446ADEMO1Z Dual Channel Step Down Regulator
User Guide
FIGURE 1. ISL6446ADEMO1Z REV B BOARD
FIGURE 2. ISL6446ADEMO1Z REV B BOARD BACKSIDE
Introduction
Evaluation Board Features
The ISL6446A is a high performance Dual PWM + Single
Linear Controller. This device integrates complete control,
monitoring and protection functions for two synchronous buck
PWM controllers and one low power linear controller. Each
PWM channel is switched 180° out-of-phase for reduced input
ripple current and lower EMI.
• 12V input voltage
The PWM controller uses voltage mode control for simple
output regulation. The output can be regulated from 0.8*VIN
down to the 0.6V reference voltage. Switching frequency is
programmable from 100kHz to 2.5MHz, providing either a cost
optimized or compact power solution.
• Efficiency up to 94.9%
The ISL6446ADEMO1Z demo board is designed as an easy to
use, dual output, non-isolated power module featuring
synchronous buck function. It is well suited for any
applications that require high performance, small space and
low cost. The ISL6446ADEMO1Z output voltage is preset to
3.3V and 5V targeting ATX power supply applications. Each
channel is designed for up to 20A of output current. Total
power of the demo board is limited by thermal conditions.
• Over-temperature protection
• Preset +5V and +3.3V output
• 20A output current each channel
• Two-in-1 PWM controller with out-of-phase operation
• Voltage-mode PWM control
• Prebias start-up
• Undervoltage lockout
• Output overcurrent protection
• fsw set at 280kHz
• Simple dual layer board design
Evaluation Board Specifications
SYMBOL
1
TEST
CONDITIONS
MIN TYP MAX UNIT
Input Range
Over IO range
10.8
VOUT1
Output Range
Over IO range
4.8
IOUT1
Output Current
From no load to
full load
VOUT2
Output Range
Over IO range
IOUT2
Output Current
From no load to
full load
VIN
May 7, 2015
AN1822.1
PARAMETER
5
0
3.1
0
3.3
13.2
V
5.2
V
20
A
3.5
V
20
A
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC 2014, 2015. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
Application Note 1822
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Evaluation Board Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Evaluation Board Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Terminal Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Undervoltage Lockout Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
ISL6446ADEMO1Z Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
PCB Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
ISL6446ADEMO1Z Bill of Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
ISL6446ADEMO1Z Test Report. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Efficiency Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Steady State Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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Application Note 1822
Equipment Used for Validation
Getting Started
• 12V/200W input power source
Using short twisted pair leads for any power connections and
with all loads and power supplies off, refer to Figure 4 for the
proper measurement and equipment setup. The Power Supply
(PS) should not be connected to the circuit until told to do so in
the following procedure.
• Dual channel electronic load
VIN
INPUT DC
POWER
3.3V
ISL6446ADEMO1Z
GND
5V
ELECTRONIC
LOAD
ELECTRONIC
LOAD
When measuring the input or output voltage ripple, care must be
taken to avoid a long ground lead on the oscilloscope probe.
Measure the input or output voltage ripple by touching the probe
tip directly across VOUT and GND terminals.
+
V
-
FIGURE 3. TYPICAL APPLICATION DIAGRAM
Terminal Functions
TABLE 1. TERMINAL FUNCTIONS
TERMINAL
NAME
The positive input voltage node to the module, which is
referenced to common GND.
GND
This is the common ground connection for the VIN and
VOUT power connection.
3.3V
+A +
POWER
SUPPLY
-
The regulated positive 5V power output with respect to the
GND node.
The regulated positive 3.3V power output with respect to
the GND node.
V
+
-
V
+ A -
3.3V
VIN
ISL6446ADEMO1Z
LOAD
+A -
5V
GND
LOAD
DESCRIPTION
VIN
5V
+
FIGURE 4. CONNECTION DIAGRAM
1. Keep the power supply and electronic load power off.
2. Connect the power supply; electronic load; voltage and
current meters. Figure 4 shows while keeping the power
supply and load shut down.
3. Turn on the power supply and set the input voltage to 12V.
Monitor input current. If input current exceeds 100mA, turn
off power supply and look for shorts.
4. Confirm VOUT1 = 3.3V, VOUT2 = 5V
5. Slowly increase the load on VOUT to 15A. Verify VOUT1 = 3.3V,
VOUT2 = 5V
The board is now ready for operation.
Undervoltage Lockout Circuit
The ISL6446ADEMO1Z demo board includes as part of its
circuitry a UVLO (Undervoltage Lockout) circuit that prevents it
from starting up with VIN voltages less than about 7.8V. If you
want to reduce the UVLO voltage, (resistor R12 in the schematic
of the board) it needs to be reduced in value.
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Application Note 1822
Board Electrical Specifications
(unless otherwise noted).
SYMBOL
VIN
TA = +25°C; VIN = 12V; VOUT1 = 3.3V, VOUT2 = 5V, and IOUT1 = 15A, IOUT2 = 15A
PARAMETER
TEST CONDITIONS
MIN
Input Range
Over IO range
10.8
VOUT1
Output Range
Over IO range
4.8
IO1
Output Current
From no load to full load
VOUT2
Output Range
Over IO range
IO2
Output Current
From no load to full load
VIN = 12V
(Note 1)
η
Vr1
Vr2
VOUT2 Ripple (Peak-to-peak)
5
0
3.1
3.3
0
MAX
UNIT
13.2
V
5.2
V
20
A
3.5
V
20
A
IOUT1 = IOUT2 = 2A
93.39
%
IOUT1 = IOUT2 = 4A
95.18
%
IOUT1 = IOUT2 = 8A
95.87
%
IOUT1 = IOUT2 = 12A
95.53
%
IOUT1 = IOUT2 = 16A
94.88
%
IOUT1 = IOUT2 = 20A
93.99
%
No load
30
mVP-P
Full load
50
mVP-P
No load
30
mVP-P
Full Load
50
mVP-P
Efficiency for DC/DC
VOUT1 Ripple (Peak-to-peak)
TYP
V T1
Transient (Peak-to-peak)
Output peak-to-peak voltage variation when
output current changing from 5A to 10A with
2.5A/µs slew rate
250
mV
V T2
Transient (Peak-to-peak)
Output peak-to-peak voltage variation when
output current changing from 5A to 10A with
2.5A/µs slew rate
250
mV
Fs
Switching Frequency
Over VIN and Io range
280
kHz
NOTE:
1. For the efficiency test result please refer to page 11.
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ISL6446ADEMO1Z Schematic
5V
R18
20
C42
1UF
VIN
R1
10K
C20
22UF
R3
110K
R9
1.3K
Q5
5
C7
R4
15K
5VS
Q6
C10 0.47UF
1
1000PF
2
3
C13
0.01UF
4
Q12
C26
47UF
R11 56K
5
6
R19
20
7
C12
1000PF
8
R8 10K
C14
0.01UF
FB2
9
10
R5
68K
C8
C6
0.47UF
VIN
C9
11
12
DNP
R10 1.3K
C3
1000PF
SS2
OCSET1
VIN
SS1/EN1
BOOT1
COMP1
UGATE1
FB1
PHASE1
RT
LGATE1
SGND
VCC
LCDR
PGND
LCFB
LGATE2
FB2
PHASE2
COMP2
UGATE2
SS2/EN2
BOOT2
OCSET2
PGOOD
ISL6446A
C16
1UF
22
21
PH1
C18
0.1UF
C17
4.7UF
20
VIN
19
18
C21
22UF
17
16
PH2
Q7
C19
22UF
C23
270UF
Q9
15
L3
L1
14
PH2
C15
0.1UF
3V3S
VIN
5V
1
2
3
4
5
6
7
8
9
10
13
Q8
0.2UH
Q10
C27
47UF
R16 0
1000PF
SS1
SS2
R15
20K
R12
100K
Q3
2N7002
Q4
2N7002
Q2
NPN
CON10
R13
9.1K
3V3
2UH
J1
3V3
C41
10UF
23
VIN
R6
15K
C28
47UF
24
FB2
C4
220PF
C29
820UF
R14
51K
Q1
2N7002
Title
<Title>
Size
B
AN1822.1
May 7, 2015
FIGURE 5. ISL6446ADEMO1Z SCHEMATIC
Document Number
<Doc>
C25
47UF
C30
820UF
C40
10UF
Application Note 1822
3V3
5V
0.2UH
U1
C11
R2
10K
L4
L2
PH1
2UH
R7 10K
C43
1UF
Q11
R17
0
1000PF
C5 DNP
C2
220PF
C24
270UF
VIN
VIN
C1
1000PF
C22
22UF
Application Note 1822
PCB Layout
FIGURE 6. SILK SCREEN TOP
FIGURE 7. SILK SCREEN BOTTOM
FIGURE 8. PCB TOP
FIGURE 9. PCB BOTTOM
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Application Note 1822
ISL6446ADEMO1Z Bill of Materials
MANUFACTURER PART
QTY
UNIT
S
ISL6446ADEMO1ZREVBPCB
1
ea.
06035C102KAT2A
6
ea. C1, C3, C7, C9, CAP, SMD, 0603, 1000pF, 50V, 10%, X7R, ROHS
C11, C12
GRM39X7R103K050
2
ea. C13, C14
CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, ROHS
MURATA
GRM39X7R104K025AD
2
ea. C15, C18
CAP, SMD, 0603, 0.1µF, 25V, 10%, X7R, ROHS
MURATA
GRM188R61C105KA12D
3
ea. C16, C42, C43 CAP, SMD, 0603, 1µF, 16V, 10%, X5R, ROHS
MURATA
GRM188R71H221KA01D
2
ea. C2, C4
CAP, SMD, 0603, 220pF, 50V, 10%, X7R, ROHS
MURATA
C1608X7R1C474K
2
ea. C8, C10
CAP, SMD, 0603, 0.47µF, 16V, 10%, X7R, ROHS
TDK
ECJ-2FB1C475K
1
ea. C17
CAP, SMD, 0805, 4.7µF, 16V, 10%, X5R, ROHS
PANASONIC
C1206X7R100-106KNE
2
ea. C40, C41
CAP, SMD, 1206, 10µF, 10V, 10%, X7R, ROHS
VENKEL
GRM32ER71C226KE18L
4
ea. C19, C20, C21, CAP, SMD, 1210, 22µF,16V, 10%, X7R, ROHS
C22
MURATA
ECJ-4YB0J476M
4
ea. C25, C26, C27, CAP, SMD, 1210, 47µF, 6.3V, 20%, X5R, ROHS
C28
PANASONIC
PA2509.201NL
2
ea. L3, L4
COIL-PWR INDUCTOR, SMD, 7X8.5, 0.2µH, 12%, 32A, 0.35mΩ, ROHS
RL80J821MDN1KX
2
ea. C29, C30
CAP, TH, RADIAL, 820µF, 6.3V, 20%, ALUM.POLYMER, 3.5mmLS, ROHS
NICHICON
RL81C271MDN1KX
2
ea. C23, C24
CAP, TH, RADIAL, 270µF, 16V, 20%, ALUM.POLYMER, 3.5mmLS, ROHS
NICHICON
SER2011-202MLB
2
ea. L1, L2
COIL-PWR INDUCTOR, SMD, 18.7X19.1, 2.0µH, 20%, 37A, 1.2mΩ, ROHS
COILCRAFT
1-640385-0
1
ea. J1
CONN-HEADER, TH, 1X10, NYLON, R/A, 0.156mmPITCH, ROHS
ISL6446AIAZ
1
ea. U1
IC-DUAL PWM/LINEAR CONTROLLER, 24P, QSOP, ROHS
2N7002-7-F
3
ea. Q1, Q3, Q4
TRANSISTOR, N-CHANNEL, 3LD, SOT-23, 60V, 115mA, ROHS
DIODES, INC.
BSC010NE2LS
4
ea. Q7, Q8, Q11,
Q12
TRANSIST-MOS, N-CHANNEL, 8P, PG-TDSON-8, 25V, 100A, ROHS
INFINEON
TECHNOLOGY
MMBT3904
1
ea. Q2
TRANSISTOR-NPN, SMD, SOT-23, 40V, 200mA, 350mW, ROHS
FAIRCHILD
ERJ-3EKF20R0V
2
ea. R18, R19
RES, SMD, 0603, 20Ω, 1/10W, 1%, TF, ROHS
PANASONIC
CR0603-10W-000T
2
ea. R16, R17
RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS
RK73H1JT1002F
4
ea. R1, R2, R7, R8 RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS
CR0603-10W-1003FT
1
ea. R12
RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS
VENKEL
ERJ-3EKF1103V
1
ea. R3
RES, SMD, 0603, 110k, 1/10W, 1%, TF, ROHS
PANASONIC
CRCW06031K30FKTA
2
ea. R9, R10
RES, SMD, 0603, 1.3k, 1/10W, 1%, TF, ROHS
VISHAY/DALE
ERJ-3EKF1502V
2
ea. R4, R6
RES, SMD, 0603, 15k, 1/10W, 1%, TF, ROHS
PANASONIC
CR0603-10W-2002FT
1
ea. R15
RES, SMD, 0603, 20k, 1/10W, 1%, TF, ROHS
VENKEL
RC0603FR-0751KL
1
ea. R14
RES, SMD, 0603, 51k, 1/10W, 1%, TF, ROHS
YAGEO
ERJ-3EKF5602V
1
ea. R11
RES, SMD, 0603, 56k, 1/10W, 1%, TF, ROHS
PANASONIC
RC0603FR-0768KL
1
ea. R5
RES, SMD, 0603, 68k, 1/10W, 1%, TF, ROHS
YAGEO
CR0603-10W-9101FT
1
ea. R13
RES, SMD, 0603, 9.1k, 1/10W, 1%, TF, ROHS
VENKEL
SJ-5003SPBL
4
ea. Bottom four
corners
BUMPONS, 0.44inW x 0.20inH, DOMETOP, BLACK
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REFERENCE
DESIGNATOR
DESCRIPTION
PWB-PCB, ISL6446ADEMO1Z, REVB, ROHS
MANUFACTURER
IMAGINEERING
INC
AVX
PULSE
TE CONNECTIVITY
INTERSIL
VENKEL
KOA
3M
AN1822.1
May 7, 2015
Application Note 1822
ISL6446ADEMO1Z Test Report
VIN = 12V, NO LOAD START-UP
5V
VIN = 12V, FULL LOAD START-UP
5V
3.3V
3.3V
VIN
VIN
FIGURE 10. START-UP
VIN = 12V, NO LOAD SHUTDOWN
FIGURE 11. START-UP
VIN = 12V, FULL LOAD SHUTDOWN
5V
5V
3.3V
3.3V
VIN
VIN
FIGURE 12. SHUTDOWN
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FIGURE 13. SHUTDOWN (UVLO VOLTAGE 7.4V)
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May 7, 2015
Application Note 1822
Efficiency Curves
Input = 12VDC, Output = 5V/20A, 3.3V/20A.
97
12
FULL LOAD 5V/20A, 3.3V/20A
10
9
95
POWER LOSS (W)
EFFICIENCY (%)
FULL LOAD 5V/20A, 3.3V/20A
11
96
94
93
92
8
7
6
5
4
3
2
91
1
90
0
20
40
60
80
100
120
LOAD POWER (W)
140
160
0
180
0
5.04
60
80
100
120
LOAD POWER (W)
140
160
180
3.36
5.03
3.35
5.02
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
40
FIGURE 15. POWER LOSS vs OUTPUT POWER
FIGURE 14. EFFICIENCY vs OUTPUT POWER
5.01
5.00
4.99
4.98
3.34
3.33
3.32
3.31
4.97
4.96
20
0
2
4
6
8
10
12
14
16
OUTPUT CURRENT (A)
18
20
FIGURE 16. OUTPUT LOAD REGULATION 5V
Steady State Operation
22
3.30
0
2
4
6
8
10
12
14
16
OUTPUT CURRENT (A)
18
20
22
FIGURE 17. OUTPUT LOAD REGULATION 3.3V
1st stage LC (2µH + 2*47µF) + 2nd stage LC Output Filters (200nH + 820µF).
NO LOAD, HIGH-SIDE MOS TURNS OFF
LOW-SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
20A LOAD, HIGH-SIDE MOS TURNS OFF
LOW-SIDE MOS TURNS ON
PHASE
PHASE
LGATE
LGATE
FIGURE 18. GATE DRIVER AND SWITCHING TRANSIENT
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FIGURE 19. GATE DRIVER AND SWITCHING TRANSIENT
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May 7, 2015
Application Note 1822
Steady State Operation
1st stage LC (2µH + 2*47µF) + 2nd stage LC Output Filters (200nH + 820µF). (Continued)
NO LOAD, LOW-SIDE MOS TURNS OFF
HIGH-SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
PHASE
LGATE
FIGURE 20. GATE DRIVER AND SWITCHING TRANSIENT
V IN = 12V, NO LOAD OUTPUT RIPPLE
PHASE
PHASE
FULL LOAD, LOW-SIDE MOS TURNS OFF
HIGH-SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
PHASE
LGATE
FIGURE 21. GATE DRIVER AND SWITCHING TRANSIENT
NO LOAD,
LOW SIDE MOS TURNS OFF
V
IN = 12V, NO LOAD OUTPUT RIPPLE
HIGH
SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
PHASE
PHASE
PHASE
5V AC-COUPLED
FIGURE 22. 5V NO LOAD OUTPUT RIPPLE 10mV
V INLOAD,
= 12V,LOW
FULL
LOAD
NO
SIDE
MOSOUTPUT
TURNS RIPPLE
OFF
HIGH SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
PHASE
PHASE
PHASE
3.3V
AC-COUPLED
LGATE
FIGURE 23. 3.3V NO LOAD OUTPUT RIPPLE 13mV
V INLOAD,
= 12V,LOW
FULL
LOAD
OUTPUT
NO
SIDE
MOS
TURNS RIPPLE
OFF
HIGH SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIMEPHASE
PHASE
PHASE
LGATE
5V
AC-COUPLED
3.3V AC-COUPLED
LGATE
FIGURE 24. 5V FULL LOAD OUTPUT RIPPLE 25mV
FIGURE 25. 3.3V FULL LOAD OUTPUT RIPPLE 29mV
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Application Note 1822
Output Transient Responses
20A LOAD, HIGH SIDE MOS TURNS OFF
5VSIDE
OUTPUT
LOW
MOS TURNS ON
50mV/DIV
AC-COUPLED
5VAC
5V OUTPUT
50m/DIV
AC-COUPLED
5VAC
FIGURE 26. 5A~10A, 2.5A/µs, PEAK-TO-PEAK RIPPLE 226mV
3VLOAD,
OUTPUT
NO
LOW SIDE MOS TURNS OFF
50mV/DIV
HIGH
SIDE MOS TURNS ON
AC-COUPLED
THERE
IS ENOUGH DEAD TIME
FIGURE 27. 10A~15A, 2.5A/µs, PEAK-TO-PEAK RIPPLE 227mV
3V OUTPUT
FULL
LOAD, LOW SIDE MOS TURNS OFF
50mV/DIV
HIGH
SIDE MOS TURNS ON
AC-COUPLED
THERE
IS ENOUGH DEAD TIME
PHASE
PHASE
LGATE
LGATE
FIGURE 28. 5A~10A, 2.5A/µs, PEAK-TO-PEAK RIPPLE 200mV
FIGURE 29. 10A~15A, 2.5A/µs, PEAK-TO-PEAK RIPPLE 205mV
Protection
3.3V OCP PROTECTION
5V OCP PROTECTION
IO
PHASE
FIGURE 30. OVERCURRENT PROTECTION
IO
PHASE
FIGURE 31. OVERCURRENT PROTECTION
Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is
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