ISL6431A
Advanced Pulse Width Modulation (PWM) Controller for Broadband Applications

Key Features

• Operates from +5V Input
• 0.8V to V_IN Output Range
• 0.8V Internal Reference
• ±1.5% Over 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
• 300kHz Fixed Frequency Oscillator
• Internal Soft Start
• 8-Lead SOIC Package

Description

The ISL6431A is a high efficiency, fixed frequency, synchronous buck PWM controller. It is designed for use in applications that convert 5V to lower distributed voltages required for DSL modems, cable and DSL routers and broadband gateway core processor, memory and peripheral power supplies.

The ISL6431A makes simple work out of implementing a complete control and protection scheme for a DC-DC stepdown converter. Designed to drive N-channel MOSFETs in a synchronous buck topology, the ISL6431A integrates the control, output adjustment, monitoring and protection functions into a single 8-Lead package.

The ISL6431A provides simple, single feedback loop, voltage-mode 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. The device is capable of sinking, as well as sourcing current. A fixed frequency oscillator reduces design complexity, while balancing typical application cost and efficiency.

The error amplifier features a 15MHz gain-bandwidth product and 8V/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/DSL Routers and DSL Modems
• DSP and Core Communications Processor Supplies
• Broadband Gateways
• Memory Supplies
• Industrial Power Supplies
• 5V-Input DC-DC Regulators
• Low-Voltage Distributed Power Supplies