DATASHEET
ISL6420
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.
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
overvoltage protection circuit prevents the output voltage
from going above typically 115% of the set point. Protection
from overcurrent conditions is provided by monitoring the
r
DS(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.
FN9151
Rev 5.00
Feb 13, 2008
Features
• Operates from 4.5V to 16V Input
• 0.6V Internal Reference Voltage
- ±1.0% Reference Voltage Accuracy
• 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 r
DS(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
• Also Available in QSOP Package
• Pb-Free Available (RoHS Compliant)
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
FN9151 Rev 5.00
Feb 13, 2008
Page 1 of 20
ISL6420
Pinouts
ISL6420
(20 LD QFN)
TOP VIEW
PHASE
UGATE
LGATE
BOOT
PVCC
CDEL
PGND
LGATE
PVCC
GPIO2
GPIO1/REFIN
OCSET
REFOUT
VMSET/MODE
1
2
3
4
5
6
VCC5
7
VIN
8
SGND
9
RT
10
FB
15 PGND
14 CDEL
13 PGOOD
12 ENSS
11 COMP
PHASE
UGATE
BOOT
GPIO2
GPIO1/REFIN
1
2
3
4
5
6
7
8
9
ISL6420
(20 LD QSOP)
TOP VIEW
20 PGOOD
19 ENSS
18 COMP
17 FB
16 RT
15 SGND
14 VIN
13 VCC5
12 VMSET/MODE
11 REFOUT
20
19
18
17
16
OCSET 10
Ordering Information
PART NUMBER
ISL6420IR
ISL6420IR-T*
ISL6420IRZ (Note)
ISL6420IRZ-T* (Note)
ISL6420IRZ-TK* (Note)
ISL6420IA
ISL6420IA-TK*
ISL6420IAZ (Note)
ISL6420IAZ-TK* (Note)
PART MARKING
ISL 6420IRZ
ISL 6420IRZ
64 20IRZ
64 20IRZ
64 20IRZ
ISL 6420IA
ISL 6420IA
ISL 6420IAZ
ISL 6420IAZ
TEMP.
RANGE (°C)
-40 to +85
PACKAGE
20 Ld 4x4 QFN
PKG.
DWG. #
L20.4x4
L20.4x4
L20.4x4
L20.4x4
L20.4x4
M20.15
M20.15
20 Ld QSOP (Pb-free)
M20.15
M20.15
20 Ld 4x4 QFN Tape and Reel
-40 to +85
20 Ld 4x4 QFN (Pb-free)
20 Ld 4x4 QFN Tape and Reel (Pb-free)
20 Ld 4x4 QFN Tape and Reel (Pb-free)
-40 to +85
20 Ld QSOP Tape and Reel
-40 to +85
20 Ld QSOP
20 Ld QSOP Tape and Reel (Pb-free)
*Please refer to TB347 for details on reel specifications.
NOTE: These Intersil Pb-free plastic packaged products employ special Pb-free material sets; molding compounds/die attach materials and 100%
matte tin plate PLUS ANNEAL - e3 termination finish, which is 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.
FN9151 Rev 5.00
Feb 13, 2008
Page 2 of 20
ISL6420
Functional Block Diagram
VCC5
SGND
LDO
PHASE
SS
REFERENCE
0.6V
OVERCURRENT
COMP
+
-
OCFLT
OVFLT
UVFLT
VIN
OCSET
BOOT
UGATE
PHASE
PHASE
LOGIC
PVCC
LGATE
PGND
FAULT
LOGIC
FB
COMP
GPIO1/REFIN
GPIO2
REFOUT
VMSET/MODE
VOLTAGE
MARGINING
+
ERROR
AMP
+
-
-
PWM
COMP
PWM
LOGIC
RAMP
GENERATOR
FB
OV/UV
VOLTAGE
MONITOR
OVFLT
UVFLT
OSC
EN/SS
PGOOD
CDEL
RT
ENSS
Typical 5V Input DC/DC Application Schematic
5V
C1
C2
VIN
PVCC
C3
VCC5
OCSET
BOOT
Q1
OSC
REF
--
+
+
LGATE
PGND
GPIO1/REFIN
R6
R5
R4
C12
REFOUT
GPIO2
Q2
C10
UGATE
PHASE
C9
L1
3.3V
R1
C4
C5
D1
C6
ENSS
RT
C7
0.1µF
PGOOD
R2
CDEL
C8
SGND
FB
R3
C11
+
+
--
MONITOR AND
PROTECTION
COMP
C13
VMSET/MODE
FN9151 Rev 5.00
Feb 13, 2008
Page 3 of 20
ISL6420
Typical 12V Input DC/DC Application Schematic
12V
C1
C2
VIN
PVCC
C3
VCC5
OCSET
BOOT
Q1
OSC
REF
--
+
+
LGATE
PGND
Q2
C10
UGATE
PHASE
C9
L1
3.3V
R1
C4
C5
D1
C6
ENSS
RT
R2
C8
PGOOD
CDEL
SGND
FB
R3
C11
R5
R4
+
+
--
MONITOR AND
PROTECTION
C7
COMP
R6
GPIO1/REFIN
REFOUT
GPIO2
C12
C13
VMSET/MODE
Typical 5V Input DC/DC Application Schematic
5V
C1
C2
VIN
PVCC
C3
VCC5
OCSET
BOOT
Q1
OSC
REF
SGND
FB
R3
C10
C11
+
+
--
COMP
REFOUT
C12
R4
VMSET/MODE
VCC5
CONFIGURATION FOR DDR TERMINATION/EXTERNALLY REFERENCED TRACKING APPLICATIONS
--
+
+
LGATE
PGND
Q2
C9
UGATE
PHASE
C8
L1
2.5V/1.25V
R1
C4
C5
D1
C6
SS/EN
RT
CDEL
C7
R2
PGOOD
MONITOR AND
PROTECTION
GPIO1/REFIN <-- VREF = VDDQ/2
GPIO2
1.25V VREF
TO REFIN OF VTT SUPPLY
R5
FN9151 Rev 5.00
Feb 13, 2008
Page 4 of 20
ISL6420
Typical 12V Input DC/DC Application Schematic
12V
C6
C1
C2
VIN
PVCC
C3
VCC5
OCSET
BOOT
Q1
OSC
REF
SGND
FB
R3
+
+
--
COMP
--
+
+
LGATE
PGND
Q2
C9
UGATE
PHASE
C8
L1
2.5V/1.25V
VDDQ/VTT
R1
C4
C5
D1
SS/EN
RT
R2
CDEL
PGOOD
MONITOR AND
PROTECTION
C7
C10
C11
GPIO1/REFIN <-- VREF = VDDQ/2
GPIO2
REFOUT
C12
R5
1.25V VREF
TO REFIN OF VTT SUPPLY
R4
VMSET/MODE
VCC5
CONFIGURATION FOR DDR TERMINATION/EXTERNALLY REFERENCED TRACKING APPLICATIONS
FN9151 Rev 5.00
Feb 13, 2008
Page 5 of 20
