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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.

Key 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
• Phase dropping facilitated with companion FET driver ISL78420 (featuring tri-level input control)
• 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

Applications

• Automotive power supplies
  • Start/stop DC/DC converter
  • Electronic power steering systems (EPAS)
  • Fuel pumps
  • Injection system
• Audio trunk amplifier power supplies