ISL6420A
NOT REC
OM
RECOMM MENDED FOR N
EW D ES
ENDED R
IGN
EPL AC E
MENT PA S
ISL6420
RT
B
DATASHEET
FN9169
Rev 4.00
December 4, 2009
Advanced Single Synchronous Buck Pulse-Width Modulation (PWM) Controller
The ISL6420A simplifies the implementation of a
complete control and protection scheme for a
high-performance DC/DC buck converter. It is designed
to drive N-Channel MOSFETs in a synchronous rectified
buck topology. The ISL6420A 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 ISL6420A 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 ISL6420A 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.
Features
• Operates From:
- 4.5V to 5.5V Input
- 5.5V to 28V Input
• 0.6V Internal Reference Voltage
- ±1.0% Reference 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
• Diode Emulation during Startup for Pre-Biased
Load Applications
• Offered in 20 Ld QFN and QSOP Packages
• 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 (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
FN9169 Rev 4.00
December 4, 2009
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