ISL6439A
Single Sync Buck PWM Controller for Broadband Gateway Applications

Key Features

• Operates from 3.3V to 5V Input
• 0.8V to VIN Output Range
• 0.8V Internal Reference
• ±1.5% Over Load, Line Voltage and Temperature
• 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
• Lossless, Programmable Overcurrent Protection
• Uses Upper MOSFET's r_DS(ON)
• Converter can Source and Sink Current
• Small Converter Size
• Internal Fixed Frequency Oscillator
• ISL6439: 300kHz
• ISL6439A: 600kHz
• Internal Soft-Start
• 14 Pin SOIC or 16 Lead 5x5 QFN
• QFN Package:
• Compliant to JEDEC PUB95 MO-220 QFN - Quad Flat No Lead - Package Outline
• Near Chip Scale Package footprint, which improves PCB efficiency and has a thinner profile
• Pb-free (RoHS compliant)

Description

The ISL6439 makes easy work out of implementing a complete control and protection scheme for a DC/DC step-down converter. Designed to drive N-Channel MOSFETs in a synchronous buck topology, the ISL6439 integrates the control, output adjustment, monitoring and protection functions into a single package.

The ISL6439 provides simple, single feedback loop, voltagemode control with fast transient response. The output voltage can be precisely regulated to as low as 0.8V, with a maximum tolerance of ±1.5% over temperature and line voltage variations. A fixed frequency oscillator reduces design complexity, while balancing typical application cost and efficiency.

The error amplifier features a 15MHz gain-bandwidth product and 6V/µs slew rate which enables high converter bandwidth for fast transient performance. The resulting PWM duty cycles range from 0% to 100%.

Protection from overcurrent conditions is provided by monitoring the r_DS(ON) of the upper MOSFET to inhibit PWM operation appropriately. This approach simplifies the implementation and improves efficiency by eliminating the need for a current sense resistor.

Applications

• Cable Modems, Set Top Boxes, and DSL Modems
• DSP and Core Communications Processor Supplies
• Memory Supplies
• Personal Computer Peripherals
• Industrial Power Supplies
• 3.3V-Input DC/DC Regulators
• Low-Voltage Distributed Power Supplies