March 19, 2009
Phase Doubler with Integrated Drivers
and Phase Shedding Function
www.TdahteasIhSeLe6t46u1.1cAomutilizes Intersil’s proprietary Phase Doubler
scheme to modulate two-phase power trains with single
PWM input. It doubles the number of phases that Intersil’s
ISL63xx multiphase controllers can support. At the same
time, the PWM line can be pulled high to disable the
corresponding phase or higher phase(s) when the enable
pin (EN_PH) is pulled low. This simplifies the phase
shedding implementation. For layout simplicity and
improving system performance, the device integrates two 5V
drivers (ISL6609) and current balance function.
The ISL6611A is designed to minimize the number of analog
signals interfacing between the controller and drivers in high
phase count and scalable applications. The common COMP
signal, which is usually seen with conventional cascaded
configuration, is not required; this improves noise immunity
and simplifies the layout. Furthermore, the ISL6611A
provides low part count and a low cost advantage over the
conventional cascaded technique.
The IC is biased by a single low voltage supply (5V),
minimizing driver switching losses in high MOSFET gate
capacitance and high switching frequency applications.
Bootstrapping of the upper gate driver is implemented via an
internal low forward drop diode, reducing implementation
cost, complexity, and allowing the use of higher
performance, cost effective N-Channel MOSFETs. Adaptive
shoot-through protection is integrated to prevent both
MOSFETs from conducting simultaneously.
The ISL6611A features 4A typical sink current for the lower
gate driver, enhancing the lower MOSFET gate hold-down
capability during PHASE node rising edge, preventing power
loss caused by the self turn-on of the lower MOSFET due to
the high dV/dt of the switching node.
The ISL6611A also features an input that recognizes a
high-impedance state, working together with Intersil
multiphase PWM controllers to prevent negative transients
on the controlled output voltage when operation is
suspended. This feature eliminates the need for the Schottky
diode that may be utilized in a power system to protect the
load from negative output voltage damage.
In addition, the ISL6611A’s bootstrap function is designed to
prevent the BOOT capacitor from overcharging, should
excessively large negative swings occur at the transitions of
the PHASE node.
• Proprietary Phase Doubler Scheme with Phase Shedding
Function (Patent Pending)
- Enhanced Light to Full Load Efficiency
• Patented Current Balancing with rDS(ON) Current Sensing
and Adjustable Gain
• Quad MOSFET Drives for Two Synchronous Rectified
Bridge with Single PWM Input
• Channel Synchronization and Interleaving Options
• Adaptive Zero Shoot-Through Protection
• 0.4Ω On-Resistance and 4A Sink Current Capability
• 36V Internal Bootstrap Schottky Diode
• Bootstrap Capacitor Overcharging Prevention (ISL6611A)
• Supports High Switching Frequency (Up to 1MHz)
- Fast Output Rise and Fall
• Tri-State PWM Input for Output Stage Shutdown
• Phase Enable Input and PWM Forced High Output to
Interface with Intersil’s Controller for Phase Shedding
• QFN Package
- Compliant to JEDEC PUB95 MO-220 QFN-Quad Flat
No Leads-Product Outline
- Near Chip-Scale Package Footprint; Improves PCB
Utilization, Thinner Profile
- Pb-Free (RoHS Compliant)
• High Current Low Voltage DC/DC Converters
• High Frequency and High Efficiency VRM and VRD
• High Phase Count and Phase Shedding Applications
• Technical Brief TB363 “Guidelines for Handling and
Processing Moisture Sensitive Surface Mount Devices
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright Intersil Americas Inc. 2009. All Rights Reserved
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