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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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ISL6622
VR11.1 Compatible Synchronous
Rectified Buck MOSFET Drivers
The ISL6622 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 ISL6622 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 ISL6622
detects a PSI
protocol sent by an Intersil VR11.1 controller, it
activates Diode Emulation (DE) and Gate Voltage
Optimization Technology (GVOT) operation; otherwise, it
operates in normal Continuous Conduction Mode (CCM)
PWM mode.
In the 8 Ld SOIC package, the ISL6622 drives the upper and
lower gates to VCC during normal PWM mode, while the
lower gate drops down to a fixed 5.75V (typically) during PSI
mode. 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) during PSI
mode. This provides
the flexibility necessary to optimize applications involving
trade-offs between gate charge and conduction losses.
To further enhance light load efficiency, the ISL6622 enables
diode emulation operation during PSI
mode. This allows
Discontinuous Conduction Mode (DCM) 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
ISL6622 has a 20kΩ integrated high-side 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) become shorted.
Features
• Dual MOSFET Drives for Synchronous Rectified Bridge
• Advanced Adaptive Zero Shoot-through Protection
• Integrated LDO for Selectable Lower Gate Drive Voltage
(5.75V, 6.75V, 7.75V) to Optimize Light Load Efficiency
• 36V Internal Bootstrap Diode
• Advanced PWM Protocol (Patent Pending) to Support PSI
Mode, Diode Emulation, Three-State 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 High-Side Gate-to-Source Resistor to Prevent
from Self Turn-On due to High Input Bus dV/dt
• Pre-POR Overvoltage Protection for Start-up and
Shutdown
• Power Rails Undervoltage Protection
• Expandable Bottom Copper Pad for Enhanced Heat
Sinking
• Dual Flat No-Lead (DFN) Package
- Near Chip-Scale Package Footprint; Improves PCB
Efficiency and Thinner in Profile
• Pb-Free (RoHS Compliant)
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
Related Literature
• Technical Brief TB363 “Guidelines for Handling and
Processing Moisture Sensitive Surface Mount Devices
(SMDs)”
• Technical Brief TB417 “Designing Stable Compensation
Networks for Single Phase Voltage Mode Buck
Regulators” for Power Train Design, Layout Guidelines,
and Feedback Compensation Design
FN6470.2Data Sheet October 30, 2008
