Intersil ISL6446ADEMO1Z User manual

1
ISL6446ADEMO1Z Dual Channel Step Down Regulator
User Guide
Introduction
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.
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.
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.
Evaluation Board Features
• 12V input voltage
• 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
• Efficiency up to 94.9%
• Prebias start-up
• Undervoltage lockout
• Output overcurrent protection
• Over-temperature protection
•f
sw set at 280kHz
• Simple dual layer board design
FIGURE 1. ISL6446ADEMO1Z REV B BOARD FIGURE 2. ISL6446ADEMO1Z REV B BOARD BACKSIDE
Evaluation Board Specifications
SYMBOL PARAMETER
TEST
CONDITIONS MIN TYP MAX UNIT
VIN Input Range Over IOrange 10.8 13.2 V
VOUT1 Output Range Over IOrange 4.8 5 5.2 V
IOUT1 Output Current From no load to
full load
0 20 A
VOUT2 Output Range Over IOrange 3.1 3.3 3.5 V
IOUT2 Output Current From no load to
full load
0 20 A
Application Note 1822
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.
May 7, 2015
AN1822.1

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 2
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

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 3
Equipment Used for Validation
• 12V/200W input power source
• Dual channel electronic load
Terminal Functions
Getting Started
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.
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.
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.
TABLE 1. TERMINAL FUNCTIONS
TERMINAL
NAME DESCRIPTION
VIN 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.
5V The regulated positive 5V power output with respect to the
GND node.
3.3V The regulated positive 3.3V power output with respect to
the GND node.
FIGURE 3. TYPICAL APPLICATION DIAGRAM
VIN 3.3V
5V
GND
ISL6446ADEMO1Z ELECTRONIC
INPUT DC
LOAD
ELECTRONIC
LOAD
POWER
FIGURE 4. CONNECTION DIAGRAM
VIN 3.3V
5V
GND
ISL6446ADEMO1Z
LOAD
LOAD
POWER
SUPPLY
+
-
+
+
+
+
+
-
-
-
-
-
-
V
V V
A
+
A
A

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 4
Board Electrical Specifications TA = +25°C; VIN = 12V; VOUT1 = 3.3V, VOUT2 = 5V, and IOUT1 = 15A, IOUT2 = 15A
(unless otherwise noted).
SYMBOL PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
VIN Input Range Over IOrange 10.8 13.2 V
VOUT1 Output Range Over IOrange 4.8 5 5.2 V
IO1 Output Current From no load to full load 0 20 A
VOUT2 Output Range Over IOrange 3.1 3.3 3.5 V
IO2 Output Current From no load to full load 0 20 A
ηEfficiency for DC/DC
VIN = 12V
(Note 1)
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 %
Vr1 V
OUT1 Ripple (Peak-to-peak) No load 30 mVP-P
Full load 50 mVP-P
Vr2 V
OUT2 Ripple (Peak-to-peak) No load 30 mVP-P
Full Load 50 mVP-P
VT1 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
VT2 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.

Application Note 1822
5AN1822.1
May 7, 2015
Submit Document Feedback
ISL6446ADEMO1Z Schematic
VIN
5V
FB2
SS2
VIN
3V3
FB2
3V3
VIN
5V
VIN SS1 SS2
VIN
PH1
PH2
PH1
VIN
5VS 5V
PH2
VIN
3V3S 3V3
Title
Size Document Num ber
<Doc>
<Title>
B
Title
Size Document Num ber
<Doc>
<Title>
B
Title
Size Document Num ber
<Doc>
<Title>
B
L2
2UH
C17 4.7UF
C30
820UF
Q8
C14 0.01UF
C26
47UF
L4
0.2UH
L3
0.2UH
C41
10UF
C24
270UF
C25
47UF
C27
47UF
C23
270UF
C40
10UF
C4
220PF
C5 DNP
C21
22UF
Q11
R6
15K
Q12
R18
20
C43
1UF
C13 0.01UF
R5
68K
R2
10K
Q6
C16 1UF
R12
100K
R1
10K
R9 1.3K
C8 0.47UF
C19
22UF
R11 56K
R14
51K
R4
15K
C3
1000PF C9 1000PF
C42
1UF
C12 1000PF
R19
20
Q9
C18 0.1UF
R8 10K
C28
47UF
Q7
C29
820UF
Q4
2N7002
C20
22UF
Q1
2N7002
C22
22UF
C10 0.47UF
Q5
R16 0
C11 1000PF
C15 0.1UF
L1
2UH
Q2
NPN
Q3
2N7002
J1
CON10
1
2
3
4
5
6
7
8
9
10
C7 1000PF
R7 10K
C1
1000PF
R17
0
R13
9.1K
R3
110K
C6 DNP
U1
ISL6446A
OCSET1
1
SS1/EN1
2
COMP1
3
FB1
4
RT
5
SGND
6
LCDR
7
LCFB
8
FB2
9
COMP2
10
SS2/EN2
11
OCSET2
12 PGOOD 13
BOOT2 14
UGATE2 15
PHASE2 16
LGATE2 17
PGND 18
VCC 19
LGATE1 20
PHASE1 21
UGATE1 22
BOOT1 23
VIN 24
R10 1.3K
R15
20K
C2
220PF
Q10
FIGURE 5. ISL6446ADEMO1Z SCHEMATIC

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 6
PCB Layout
FIGURE 6. SILK SCREEN TOP FIGURE 7. SILK SCREEN BOTTOM
FIGURE 8. PCB TOP FIGURE 9. PCB BOTTOM

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 7
ISL6446ADEMO1Z Bill of Materials
MANUFACTURER PART QTY
UNIT
S
REFERENCE
DESIGNATOR DESCRIPTION MANUFACTURER
ISL6446ADEMO1ZREVBPCB 1 ea. PWB-PCB, ISL6446ADEMO1Z, REVB, ROHS IMAGINEERING
INC
06035C102KAT2A 6 ea. C1, C3, C7, C9,
C11, C12
CAP, SMD, 0603, 1000pF, 50V, 10%, X7R, ROHS AVX
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,
C22
CAP, SMD, 1210, 22µF,16V, 10%, X7R, ROHS MURATA
ECJ-4YB0J476M 4 ea. C25, C26, C27,
C28
CAP, SMD, 1210, 47µF, 6.3V, 20%, X5R, ROHS PANASONIC
PA2509.201NL 2 ea. L3, L4 COIL-PWR INDUCTOR, SMD, 7X8.5, 0.2µH, 12%, 32A, 0.35mΩ, ROHS PULSE
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 TE CONNECTIVITY
ISL6446AIAZ 1 ea. U1 IC-DUAL PWM/LINEAR CONTROLLER, 24P, QSOP, ROHS INTERSIL
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 VENKEL
RK73H1JT1002F 4 ea. R1, R2, R7, R8 RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS KOA
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 3M

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 8
ISL6446ADEMO1Z Test Report
FIGURE 10. START-UP FIGURE 11. START-UP
FIGURE 12. SHUTDOWN FIGURE 13. SHUTDOWN (UVLO VOLTAGE 7.4V)
5V
3.3V
VIN
VIN = 12V, NO LOAD START-UP
5V
3.3V
VIN
VIN = 12V, FULL LOAD START-UP
5V
3.3V
VIN
VIN = 12V, NO LOAD SHUTDOWN
5V
3.3V
VIN
VIN = 12V, FULL LOAD SHUTDOWN

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 9
Efficiency Curves Input = 12VDC, Output = 5V/20A, 3.3V/20A.
FIGURE 14. EFFICIENCY vs OUTPUT POWER FIGURE 15. POWER LOSS vs OUTPUT POWER
FIGURE 16. OUTPUT LOAD REGULATION 5V FIGURE 17. OUTPUT LOAD REGULATION 3.3V
90
91
92
93
94
95
96
97
0 20 40 60 80 100 120 140 160 180
LOAD POWER (W)
EFFICIENCY (%)
FULL LOAD 5V/20A, 3.3V/20A
0
1
2
3
4
5
6
7
8
9
10
11
12
0 20 40 60 80 100 120 140 160 180
LOAD POWER (W)
POWER LOSS (W)
FULL LOAD 5V/20A, 3.3V/20A
4.96
4.97
4.98
4.99
5.00
5.01
5.02
5.03
5.04
0 2 4 6 8 10 12 14 16 18 20 22
OUTPUT CURRENT (A)
OUTPUT VOLTAGE (V)
3.30
3.31
3.32
3.33
3.34
3.35
3.36
0 2 4 6 8 10 12 14 16 18 20 22
OUTPUT CURRENT (A)
OUTPUT VOLTAGE (V)
Steady State Operation 1st stage LC (2µH + 2*47µF) + 2nd stage LC Output Filters (200nH + 820µF).
FIGURE 18. GATE DRIVER AND SWITCHING TRANSIENT FIGURE 19. GATE DRIVER AND SWITCHING TRANSIENT
PHASE
LGATE
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
LGATE

Application Note 1822
AN1822.1
May 7, 2015
Submit Document Feedback 10
FIGURE 20. GATE DRIVER AND SWITCHING TRANSIENT FIGURE 21. GATE DRIVER AND SWITCHING TRANSIENT
FIGURE 22. 5V NO LOAD OUTPUT RIPPLE 10mV FIGURE 23. 3.3V NO LOAD OUTPUT RIPPLE 13mV
FIGURE 24. 5V FULL LOAD OUTPUT RIPPLE 25mV FIGURE 25. 3.3V FULL LOAD OUTPUT RIPPLE 29mV
Steady State Operation 1st stage LC (2µH + 2*47µF) + 2nd stage LC Output Filters (200nH + 820µF). (Continued)
PHASE
NO LOAD, LOW-SIDE MOS TURNS OFF
HIGH-SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
LGATE
PHASE
FULL LOAD, LOW-SIDE MOS TURNS OFF
HIGH-SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
LGATE
PHASE
PHASE
5V AC-COUPLED
VIN = 12V, NO LOAD OUTPUT RIPPLE
PHASE
NO LOAD, LOW SIDE MOS TURNS OFF
HIGH SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
LGATE
PHASE
PHASE
VIN = 12V, NO LOAD OUTPUT RIPPLE
3.3V AC-COUPLED
PHASE
NO LOAD, LOW SIDE MOS TURNS OFF
HIGH SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
LGATE
PHASE
PHASE
VIN = 12V, FULL LOAD OUTPUT RIPPLE
5V AC-COUPLED
PHASE
NO LOAD, LOW SIDE MOS TURNS OFF
HIGH SIDE MOS TURNS ON
THERE IS ENOUGH DEAD TIME
LGATE
PHASE
PHASE
VIN = 12V, FULL LOAD OUTPUT RIPPLE
3.3V AC-COUPLED