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®
Data Sheet
July 2004
ISL6420
FN9151.2
Advanced Single Synchronous Buck
Pulse-Width Modulation (PWM) Controller
The ISL6420 makes simple work out of implementing a
complete control and protection scheme for a high-
performance DC-DC buck converter. Designed to drive
N-channel MOSFETs in a synchronous rectified buck
topology, the ISL6420 integrates control, output adjustment,
monitoring and protection functions into a single package.
Additionally, the IC features an external reference voltage
tracking mode for externally referenced buck converter
applications and DDR termination supplies, as well as a
voltage margining mode for system testing in networking
DC-DC converter applications.
The ISL6420 provides simple, single feedback loop, voltage
mode control with fast transient response. The output
voltage of the converter can be precisely regulated to as low
as 0.6V, with a maximum tolerance of ±1.0% over
temperature and line voltage variations.
The operating frequency is fully adjustable from 100kHz to
1.4MHz. High frequency operation offers cost and space
savings.
The error amplifier features a 15MHz gain-bandwidth
product and 6V/µs slew rate that enables high converter
bandwidth for fast transient response. The PWM duty cycle
ranges from 0% to 100% in transient conditions. Selecting
the capacitor value from the ENSS pin to ground sets a fully
adjustable PWM soft start. Pulling the ENSS pin LOW
disables the controller.
The ISL6420 monitors the output voltage and generates a
PGOOD (power good) signal when soft start sequence is
complete and the output is within regulation. A built-in over
voltage protection circuit prevents the output voltage from
going above typically 115% of the set point. Protection from
overcurrent conditions is provided by monitoring the rDS(ON)
of the upper MOSFET to inhibit the PWM operation
appropriately. This approach simplifies the implementation
and improves efficiency by eliminating the need for a current
sensing resistor.
Features
• Operates from 4.5V to 16V Input
• Excellent Output Voltage Regulation
- 0.6V Internal Reference
- ±1.0% Reference Accuracy Over Line and Temperature
• Resistor-Selectable Switching Frequency
- 100kHz to 1.4MHz
• Voltage Margining and External Reference Tracking
Modes
• Output Can Sink or Source Current
• Lossless, Programmable Overcurrent Protection
- Uses Upper MOSFET‘s rDS(ON)
• Programmable Soft Start
• Drives N-Channel MOSFETs
• Simple Single-Loop Control Design
- Voltage-Mode PWM Control
• Fast Transient Response
- High-Bandwidth Error Amplifier
- Full 0% to 100% Duty Cycle
• Extensive Circuit Protection Functions
- PGOOD, overvoltage, overcurrent, Shutdown
• QFN (4x4) Package
- QFN Compliant to JEDEC PUB95 MO-220 QFN - Quad
Flat No Leads - Product Outline
- QFN Near Chip Scale Package Footprint; Improves
PCB Efficiency, Thinner in Profile
• Pb-free available
Applications
• Power Supplies for Microprocessors/ASICs
- Embedded Controllers
- DSP and Core Processors
- DDR SDRAM Bus Termination
• Ethernet Routers and Switchers
• High-Power DC-DC Regulators
• Distributed DC-DC Power Architecture
• Personal Computer Peripherals
• Externally Referenced Buck Converters
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2004. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.

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Pinout
ISL6420 (QFN)
TOP VIEW
20 19 18 17 16
GPIO2 1
GPIO1 2
OCSET 3
BYPASS 4
VMSET 5
15 PGND
14 CDEL
13 PGOOD
12 ENSS
11 COMP
6 7 8 9 10
ISL6420
Ordering Information
TEMP. RANGE
PART NUMBER
(°C)
PACKAGE
PKG.
DWG. #
ISL6420IR
-40 to +85 20 Ld 4x4 QFN L20.4x4
ISL6420IR-T
20 Ld 4x4 QFN Tape and Reel L20.4x4
ISL6420IRZ
(See Note)
-40 to +85
20 Ld 4x4 QFN L20.4x4
(Pb-free)
ISL6420IRZ-T
(See Note)
20 Ld 4x4 QFN Tape and Reel L20.4x4
(Pb-free)
NOTE: Intersil Pb-free products employ special Pb-free material
sets; molding compounds/die attach materials and 100% matte tin
plate termination finish, which is 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-020B.
Functional Block Diagram
SGND
FB
COMP
GPIO1/REFIN
GPIO2
REFOUT
VMSET/MODE
VCC5 VIN
OCSET
LDO
REFERENCE
SS 0.6V
PHASE
OVER CURRENT
+-
COMP
OCFLT
OVFLT
UVFLT
FAULT
LOGIC
ERROR
+- AMP
+- PWM
COMP
PWM
LOGIC
VOLTAGE
MARGINING
FB
RAMP
GENERATOR
OV / UV
VOLTAGE
MONITOR
OVFLT
UVFLT
OSC
RT
PHASE
LOGIC
EN/SS
ENSS
BOOT
UGATE
PHASE
PVCC
LGATE
PGND
PGOOD
CDEL
2

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ISL6420
Typical 5V Input DC-DC Application Schematic
5V
C1
C7
0.1µF
R2
C8
C2 C3
VIN PVCC
VCC5
ENSS
RT
PGOOD
CDEL
SGND
FB
MONITOR AND
PROTECTION
OSC
REF
++
--
+- +-
C4 C5
OCSET R1
BOOT
UGATE
PHASE
Q1
LGATE
PGND
R3
R4
COMP
C11
R5 C12
R6
VMSET/MODE
GPIO1/REFIN
GPIO2
REFOUT
C13
Q2
D1
C9
C6
L1
C10
3.3V
Typical 12V Input DC-DC Application Schematic
12V
C7
C1
R2
C8
C2 C3
VIN PVCC
VCC5
ENSS
RT
PGOOD
CDEL
SGND
FB
MONITOR AND
PROTECTION
OSC
REF
++
--
+- +-
C4
OCSET
BOOT
UGATE
PHASE
LGATE
PGND
C5
R1
Q1
R3
R4
COMP
C11
R5 C12
GPIO1/REFIN
R6 REFOUT GPIO2
C13
VMSET/MODE
Q2
D1
C9
C6
L1
C10
3.3V
3

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ISL6420
Typical 5V Input DC-DC Application Schematic
5V
C1
C2
C3 C4 C5
VIN PVCC
VCC5
D1
SS/EN
RT
MONITOR AND
PROTECTION
OCSET R1
BOOT
Q1
CDEL
OSC
C7
R2
PGOOD
UGATE
PHASE
REF
C8
SGND
FB
++
--
+- +-
LGATE
PGND
Q2
C6
L1
C9
R3
R4
COMP
C10
C11 R5
VMSET/MODE
VCC5
GPIO1/REFIN <-- VREF=VDDQ/2
GPIO2
REFOUT
1.25V VREF
C12 TO REFIN OF VTT SUPPLY
2.5V/1.25V
CONFIGURATION FOR DDR TERMINATION/EXTERNALLY REFERENCED TRACKING APPLICATIONS
Typical 12V Input DC-DC Application Schematic
12V
C7
C1
R2
R3
C6
C2 C3
VIN PVCC
C4
VCC5
SS/EN
RT
MONITOR AND
PROTECTION
OCSET
BOOT
CDEL
PGOOD
SGND
FB
OSC
REF
++
--
+- +-
UGATE
PHASE
LGATE
PGND
C5
R1
Q1
Q2
D1
C8
L1
C9
COMP
C10
C11 R5
R4 VMSET/MODE
VCC5
GPIO1/REFIN <-- VREF=VDDQ/2
GPIO2
REFOUT
C12
1.25V VREF
TO REFIN OF VTT SUPPLY
CONFIGURATION FOR DDR TERMINATION/EXTERNALLY REFERENCED TRACKING APPLICATIONS
2.5V/1.25V
VDDQ/VTT
4

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ISL6420
Absolute Maximum Ratings (Note 1)
Bias Voltage, VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+18V
BOOT and Ugate Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +24V
ESD Classification
Human Body Model (Per MIL-STD-883 Method 3015.7) . . 1500V
Charged Device Model (Per EOS/ESD DS5.3, 4/14/93) . . 2000V
Thermal Information
Thermal Resistance (Typical)
θJA (°C/W) θJC (°C/W)
QFN Package (Notes 2, 3) . . . . . . . . .
47
8.5
Maximum Junction Temperature (Plastic Package) . . . . . . . . 150°C
Maximum Storage Temperature Range . . . . . . . . . . . -65°C to 150°C
Ambient Temperature Range. . . . . . . . . -40°C to 85°C (for “I” suffix)
Junction Temperature Range. . . . . . . . . . . . . . . . . . . -40°C to 125°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.
NOTES:
1. All voltages are with respect to GND.
2. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379.
3. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside.
Electrical Specifications
PARAMETER
VIN SUPPLY
Input Voltage Range
VIN SUPPLY CURRENT
Shutdown Current (Note 4)
Operating Current (Notes 4, 5)
VCC5 SUPPLY (Notes 5, 6)
Input Voltage Range
Output Voltage
Maximum Output Current
POWER-ON RESET
Rising VCC5 Threshold
Falling VCC5 Threshold
UVLO Threshold Hysteresis
PWM CONVERTERS
Output Voltage (Note 7)
Maximum Duty Cycle
Minimum Duty Cycle
FB pin bias current
Undervoltage Protection
Operating Conditions, Unless Otherwise Noted: VIN = 12V, PVCC shorted with VCC5, TA = 25°C
SYMBOL
TEST CONDITIONS
MIN TYP MAX
UNITS
5.6 12 16
V
ENSS = GND
- 1.4 - mA
- 2.0 3.0 mA
VIN = VCC5 for 5V configuration
4.5 5.0 5.5
V
VIN = 5.6V to 16V, IL = 3mA to 50mA 4.5 5.0 5.5
V
VIN = 12V
50 -
- mA
VIN connected to VCC5, 5V input
operation
4.32 4.4 4.45
4.09 4.1 4.25
0.16 -
-
V
V
V
VUV1
F = 300kHz
F = 300kHz
Fraction of the set point; ~3µs noise filter
0.6
90
-
-
75
- VIN - 0.5 V
96 - %
- 0%
80 - nA
- 85 %
Overvoltage Protection
VOVP1 Fraction of the set point; ~1µs noise filter 112 - 120 %
5