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®
PRELIMINARY
Data Sheet
September 9, 2005
ISL6445
FN9230.0
1.4MHz Dual, 180° Out-of-Phase,
Step-Down PWM Controller
The ISL6445 is a high-performance, dual-output PWM
controller optimized for converting wall adapter, battery or
network intermediate bus DC input supplies into the system
supply voltages required for a wide variety of applications.
Each output is adjustable down to 0.8V. The two PWMs are
synchronized 180o out of phase reducing the RMS input
current and ripple voltage.
The ISL6445 incorporates several protection features. An
adjustable overcurrent protection circuit monitors the output
current by sensing the voltage drop across the lower
MOSFET. Hiccup mode overcurrent operation protects the
DC/DC components from damage during output
overload/short circuit conditions. Each PWM has an
independent logic-level shutdown input (SD1 and SD2).
A single PGOOD signal is issued when soft-start is complete
on both PWM controllers and their outputs are within 10% of
the set point. Thermal shutdown circuitry turns off the device
if the junction temperature exceeds +150°C.
Pinout
ISL6445 (QSOP)
TOP VIEW
1 LGATE2 LGATE1 24
2 BOOT2 BOOT1 23
3 UGATE2 UGATE1 22
4 PHASE2 PHASE1 21
5 ISEN2
ISEN1 20
6 PGOOD PGND 19
7 VCC5
SD1 18
8 SD2
SS1 17
9 SS2
SGND 16
10 OCSET2 OCSET1 15
11 FB2
FB1 14
12 VIN
BIAS 13
Features
• Wide Input Supply Voltage Range
- 5.6V to 24V
- 4.5V to 5.6V
• Two Independently Programmable Output Voltages
• Switching Frequency . . . . . . . . . . . . . . . . . . . . . . .1.4MHz
• Out of Phase PWM Controller Operation
- Reduces Required Input Capacitance and Power
Supply Induced Loads
• No External Current Sense Resistor
- Uses Lower MOSFET’s rDS(ON)
• Programmable Soft-Start
• Extensive Circuit Protection Functions
- PGOOD
- UVLO
- Overcurrent
- Overtemperature
- Independent Shutdown for Both PWMs
• Excellent Dynamic Response
- Voltage Feed-Forward with Current Mode Control
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
• Power Supplies with Two Outputs
• xDSL Modems/Routers
• DSP, ASIC, and FPGA Power Supplies
• Set-Top Boxes
• Dual Output Supplies for DSP, Memory, Logic, µP Core
and I/O
• Telecom Systems
Ordering Information
PART
PART
TEMP.
PKG.
NUMBER MARKING RANGE (°C) PACKAGE DWG. #
ISL6445IAZ* ISL6445IAZ -40 to 85 24 Ld QSOP M24.15
(See Note)
(Pb-free)
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
*Add “-TK” suffix for tape and reel.
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2005. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.

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ISL6445
Typical Application Schematic
D1
BAT54HT1
C3
10µF
C4
0.1µF
VIN
SS1
17
12
BOOT1
23
C2
4.7µF
VCC5
7 9 SS2
2 BOOT2
C5
0.1µF
VCC5
+ C1
56µF
D2
BAT54HT1
C6
10µF
+12V
VOUT1
+1.8V, 2A
C9 +
150µF
R3
12.4K
R4
10K
C7
0.1µF
L1
3.2µH
Q1
FDS6912A
UGATE1 22
PHASE1 21
3 UGATE2
4 PHASE2
R1
1.4K
ISEN1 20
LGATE1 24
ISL6445IA
5 ISEN2
R2
1.4K
1 LGATE2
PGND 19
11 FB2
FB1 14
SD1 18
SD2 8
16 13
SGND
BIAS
OCSET1
15
R7
121K
OCSET2
10
R8
121K
6
PGOOD
C8
0.1µF
L2
3.2µH
Q2
FDS6912A
R9
10K
VCC5
+ C10
150µF
VOUT2
+3.3V, 2A
R5
31.6K
R6
10K
PGOOD
2 FN9230.0
September 9, 2005

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Block Diagram
BOOT1
UGATE1
PHASE1
VCC_5V
LGATE1
PGND
ADAPTIVE DEAD-TIME
DIODE EMULATION
V/I SAMPLE TIMING
FB3
FB1
SS1
180k
+ 0.8V
REF
800k
-
+
18.5pF
16k
ERROR AMP 1
ISEN1
CURRENT
SAMPLE
OCSET1
-
+ CURRENT
SAMPLE
+ 0.8V REFERENCE
PGOOD SD1
VIN SGND
SD2
VCC
UV
PGOOD
POR
ENABLE
BIAS SUPPLIES
REFERENCE
FAULT LATCH
SOFT-START
UV
PGOOD
- PWM1
+
OC1
OC2
PWM2
-
+
DUTY CYCLE RAMP GENERATOR
PWM CHANNEL PHASE CONTROL
- OC1
+
SAME STATE FOR
2 CLOCK CYCLES
REQUIRED TO LATCH
OVERCURRENT FAULT
VIN
VCC
OC2 -
+
SAME STATE FOR
2 CLOCK CYCLES
REQUIRED TO LATCH
OVERCURRENT FAULT
ADAPTIVE DEAD-TIME
DIODE EMULATION
V/I SAMPLE TIMING
PGND
BOOT2
UGATE2
PHASE2
VCC
LGATE2
18.5pF
16k
ERROR AMP 2
800k
-
180k
+
VSEN2
SOFT2
CURRENT
SAMPLE
-
+
0.8V REFERENCE +
+ 0.8V
REF
ISEN2
CURRENT
SAMPLE
OCSET2

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ISL6445
Absolute Maximum Ratings
Supply Voltage (VCC_5V Pin) . . . . . . . . . . . . . . . . . . . . -0.3V to +7V
Input Voltage (VIN Pin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+27V
BOOT1, 2 and UGATE1, 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . +35V
PHASE1, 2 and ISEN1, 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . +27V
BOOT1, 2 with Respect to PHASE1, 2 . . . . . . . . . . . . . . . . . . +6.5V
UGATE1, 2. . . . . . . . . . . . (PHASE1, 2 - 0.3V) to (BOOT1, 2 +0.3V)
Thermal Information
Thermal Resistance (Typical)
θJA (°C/W)
24 Lead QSOP (Note 1). . . . . . . . . . . . . . . . . . . . . .
85
Maximum Junction Temperature (Plastic Package) . -55°C to 150°C
Maximum Storage Temperature Range . . . . . . . . . . . -65°C to 150°C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300°C
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . -40°C to 85°C
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE:
1. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
Electrical Specifications
Recommended operating conditions unless otherwise noted. Refer to Block Diagram and Typical Application
Schematic. VIN = 5.6V to 24V, or VCC5 = 5V ±10%, TA = -40°C to 85°C (Note 3),
Typical values are at TA = 25°C
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
VIN SUPPLY
Input Voltage Range
5.6 12
24
V
VCC_5V SUPPLY (Note 3)
Input Voltage
4.5 5.0 5.6
V
Output Voltage
Maximum Output Current
SUPPLY CURRENT
VIN > 5.6V, IL = 20mA
VIN = 12V
4.5 5.0 5.5
V
60 -
- mA
Shutdown Current (Note 4)
SD1 = SD2 = GND
- 50 375 µA
Operating Current (Note 5)
- 2.0 4.0 mA
REFERENCE SECTION
Nominal Reference Voltage
- 0.8 -
V
Reference Voltage Tolerance
-1.0 - 1.0 %
POWER-ON RESET
Rising VCC_5V Threshold
4.25 4.45
4.5
V
Falling VCC_5V Threshold
3.95 4.2
4.4
V
OSCILLATOR
Total Frequency Variation
1.25 1.4 1.55 MHz
Peak-to-Peak Sawtooth Amplitude (Note 6)
Ramp Offset (Note 7)
VIN = 12V
VIN = 5V
- 1.6 -
- 0.667 -
- 1.0 -
V
V
V
SHUTDOWN1/SHUTDOWN2
HIGH Level (Converter Enabled)
Internal Pull-up (3µA)
2.0 - - V
LOW Level (Converter Disabled)
- - 0.8 V
PWM CONVERTERS
Output Voltage
- 0.8 -
V
FB Pin Bias Current
- - 150 nA
Maximum Duty Cycle
Minimum Duty Cycle
Cout = 1000pF, TA = 25°C
93 -
-%
- 4 -%
4 FN9230.0
September 9, 2005

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ISL6445
Electrical Specifications
Recommended operating conditions unless otherwise noted. Refer to Block Diagram and Typical Application
Schematic. VIN = 5.6V to 24V, or VCC5 = 5V ±10%, TA = -40°C to 85°C (Note 3),
Typical values are at TA = 25°C (Continued)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
PWM CONTROLLER ERROR AMPLIFIERS
DC Gain (Note 7)
80 88 - dB
Gain-Bandwidth Product (Note 7)
5.9 -
- MHz
Slew Rate (Note 7)
- 2.0 - V/µs
Maximum Output Voltage (Note 7)
0.9 - - V
Minimum Output Voltage (Note 7)
- - 3.6 V
PWM CONTROLLER GATE DRIVERS (Note 8)
Sink/Source Current
- 400 - mA
Upper Drive Pull-Up Resistance
VCC5 = 4.5V
-8-
Upper Drive Pull-Down Resistance
VCC5 = 4.5V
- 3.2 -
Lower Drive Pull-Up Resistance
VCC5 = 4.5V
-8-
Lower Drive Pull-Down Resistance
VCC5 = 4.5V
- 1.8 -
Rise Time
Fall Time
POWER GOOD AND CONTROL FUNCTIONS
COUT = 1000pF
COUT = 1000pF
- 18 - ns
- 18 - ns
PGOOD LOW Level Voltage
Pull-up = 100k
-
0.1 0.5
V
PGOOD Leakage Current
- - ±1.0 µA
PGOOD Upper Threshold, PWM 1 and 2
Fraction of set point
105 - 120 %
PGOOD Lower Threshold, PWM 1 and 2
Fraction of set point
80 - 95 %
ISEN and CURRENT LIMIT
Full Scale Input Current (Note 9)
- 32 - µA
Overcurrent Threshold (Note 9)
ROCSET = 110k
- 64 - µA
OCSET (Current Limit) Voltage
- 1.75 -
V
SOFT-START
Soft-Start Current
- 5 - µA
PROTECTION
Thermal Shutdown
Rising
- 150 -
°C
Hysteresis
- 20 - °C
NOTES:
2. Specifications at -40°C and 85°C are guaranteed by design, not production tested.
3. In normal operation, where the device is supplied with voltage on the VIN pin, the VCC_5V pin provides a 5V output capable of 60mA (min).
When the VCC_5V pin is used as a 5V supply input, the internal LDO regulator is disabled and the VIN input pin must be connected to the
VCC_5V pin. (Refer to the Pin Descriptions section for more details.)
4. This is the total shutdown current with VIN = VCC_5V = PVCC = 5V.
5. Operating current is the supply current consumed when the device is active but not switching. It does not include gate drive current.
6. The peak-to-peak sawtooth amplitude is production tested at 12V only; at 5V this parameter is guaranteed by design.
7. Guaranteed by design; not production tested.
8. Not production tested; guaranteed by characterization only.
9. Guaranteed by design. The full scale current of 32µA is recommended for optimum current sample and hold operation. See the Feedback Loop
Compensation Section below.
5 FN9230.0
September 9, 2005