ISL6622B
VR11.1 Compatible Synchronous Rectified Buck MOSFET Drivers

Key Features

• Dual MOSFET Drives for Synchronous Rectified Bridge
• Advanced Adaptive Zero Shoot-Through Protection
• Integrated LDO with Selectable Lower Gate Drive Voltage for Light Load Efficiency Optimization
• 36V Internal Bootstrap Diode
• Advanced PWM Protocol (Patent Pending) to Support PSI Operation
• Diode Emulation for Enhanced Light Load Efficiency
• Bootstrap Capacitor Overcharging Prevention
• Supports High Switching Frequency
• 3A Sinking Current Capability
• Fast Rise/Fall Times and Low Propagation Delays
• Integrated UGATE-to-PHASE Resistor for Increased Upper MOSFET Input Bus High dV/dt Immunity
• Pre-POR Overvoltage Protection at Start-Up and Shutdown
• Dual Flat No-Lead (DFN) Package
• Near Chip-Scale Package Footprint; Improves PCB Efficiency and Thinner in Profile
• Bottom Copper Pad for Enhanced Heat Sinking
• Pb-Free (RoHS Compliant)

Description

The ISL6622B is a high frequency MOSFET driver designed to drive upper and lower power
N-Channel MOSFETs in a synchronous rectified buck converter topology. The advanced PWM protocol of ISL6622B is specifically designed to work with Intersil VR11.1 controllers and combined with N-Channel MOSFETs, form a complete core-voltage regulator solution for advanced microprocessors. When ISL6622B detects a PSI PWM protocol sent by an Intersil VR11.1 controller, it activates Diode Emulation (DE) operation; otherwise, it operates in normal Continuous Conduction Mode (CCM) PWM mode.

In the 8 Ld SOIC package, the ISL6622B drives the upper gate to 12V while the lower drive voltage is fixed at 5.75V. The 10 Ld DFN part offers more flexibility: the upper gate can be driven from 5V to 12V via the UVCC pin, while the lower gate has a resistor-selectable drive voltage of 5.75V, 6.75V, and 7.75V (typically). This provides the flexibility necessary to optimize applications involving
trade-offs between gate charge and conduction losses.

To further enhance light load efficiency, the ISL6622B enables diode emulation operation during PSI mode. This allows for Discontinuous Conduction Mode (DCM) operation by detecting when the inductor current reaches zero and subsequently turning off the low side MOSFET to prevent it from sinking current.

An advanced adaptive shoot-through protection is integrated to prevent both the upper and lower MOSFETs from conducting simultaneously and to minimize dead time. The ISL6622B has a 20kΩ integrated high-side MOSFET gate-to-source resistor to prevent self turn-on due to high input bus dV/dt. This driver also has an overvoltage protection feature operational while VCC is below the POR threshold: the PHASE node is connected to the gate of the low side MOSFET (LGATE) via a 10kΩ resistor, limiting the output voltage of the converter close to the gate threshold of the low side MOSFET, dependent on the current being shunted, which provides some protection to the load should the upper MOSFET(s) be shorted prior to start-up.

Applications

• High Light-Load Efficiency Voltage Regulators
• Core Regulators for Advanced Microprocessors
• High Current DC/DC Converters
• High Frequency and High Efficiency VRM and VRD