ISL78225 Datasheet, PDF (1/21 Pages) Intersil Corporation – 4-Phase Interleaved Boost PWM Controller with Light Load Efficiency Enhancement

4-Phase Interleaved Boost PWM Controller with Light
Load Efficiency Enhancement
ISL78225
The ISL78225 4-phase controller is targeted for applications
where high efficiency (>95%) and high power are required. The
multiphase boost converter architecture uses interleaved timing
to multiply channel ripple frequency and reduce input and output
ripple. Lower ripple results in fewer input/output capacitors and
therefore lower component cost and smaller implementation
area.
The ISL78225 has a dedicated pin to initiate the phase dropping
scheme for higher efficiency at light load by dropping phases based
on the load current, so the switching and core losses in the converter
are reduced significantly. As the load increases, the dropped phase(s)
are added back to accommodate heavy load transients and improve
efficiency.
Input current is sensed continuously by measuring the voltage
across a dedicated current sense resistor or inductor DCR. This
current sensing provides precision channel-current balancing,
and per-phase overcurrent protection. A separate totalizing
current limit function provides overcurrent protection for all the
phases combined. This two-stage current protection provides
maximum performance and circuit reliability.
ISL78225 can also provide for input voltage tracking via the
VREF2 pin. The comparison reference voltage will be the lower of
the VREF2 pin or the internal 2V reference. By using a resistor
network between VIN and VREF2 pin, the output voltage can track
input voltage to limit the output power during automotive cranking
conditions.
ISL78225 can output a clock signal for expanding operation to
8 phases, which offers high system flexibility. The
threshold-sensitive enable input is available to accurately
coordinate the start-up of the ISL78225 with any other voltage rail.
Features
• Peak Current Mode PWM Control with Adjustable Slope
Compensation
• Precision Resistor/DCR Current Sensing
• 2, 3 or 4-Phase Operation
• Adjustable Phase Dropping/Diode Emulation/Pulse Skipping
for High Efficiency at Light Load
• Adjustable Switching Frequency or External Synchronization
from 75kHz up to 1MHz Per Phase
• Over-Temperature/Overvoltage Protection
• 2V ±1.0% Internal Reference
• Pb-Free 44-Lead 10x10 EP-TQFP (RoHS Compliant)
• -40°C to +125°C Operating Temperature Range
• AEC-Q100 Qualified
• TS16949 Compliant
Applications
• Automotive Power Supplies
- Start/Stop DC/DC Converter
- Fuel Pumps
- Injection System
• Audio Amplifier Power Supplies
• Telecom and Industrial Power Supplies
December 15, 2011
FN7909.0
0.98
WITH PHASE DROPPING
WITHOUT PHASE DROPPING
0.93
0.88
0.83
0.78
16V INPUT, 36V OUTPUT
SYNCHRONOUS BOOST
0.73
0 1 2 3 4 5 6 7 8 9 10
OUTPUT CURRENT (A)
FIGURE 1. EFFICIENCY vs OUTPUT CURRENT vs PHASE DROPPING MODE
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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