ISL6420B Datasheet, PDF (1/20 Pages) Intersil Corporation – Advanced Single Synchronous Buck Pulse-Width Modulation (PWM) Controller

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Data Sheet
April 27, 2009
ISL6420B
FN6901.0
Advanced Single Synchronous Buck
Pulse-Width Modulation (PWM) Controller
The ISL6420B 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
ISL6420B 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 ISL6420B 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 ISL6420B 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
- ±2.0% 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
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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