Analog Devices LTC3708 Product Info

• Very Low Duty Factor Operation (t_ON(MIN) < 85ns)
• No R_SENSE^™ Option for Maximum Efficiency
• Very Fast Transient Response
• Programmable Output Voltage Up/Down Tracking
• 2-Phase Operation Reduces Input Capacitance
• 0.6V ±1% Output Voltage Reference
• External Frequency Synchronization
• Monotonic Soft-Start
• On-board High Current MOSFET Drivers
• Wide V_IN Range: Up to 36V
• Adjustable Cycle-by-Cycle Current Limit
• Instant Output Overvoltage Protection
• Optional Short-Circuit Shutdown Timer
• Power Good Output with 100µs Masking
• Available in 5mm × 5mm QFN Package

The LTC3708 is a dual, 2-phase synchronous step-down switching regulator with output voltage up/down tracking capability. The IC allows either coincident or ratiometric tracking. Multiple LTC3708s can be daisy-chained in applications requiring more than two voltages to be tracked. Power supply sequencing is accomplished using an external soft-start timing capacitor.

The LTC3708 uses a constant on-time, valley current mode control architecture to deliver very low duty factors without requiring a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in input supply voltage. An internal phase-locked loop allows the IC to be synchronized to an external clock.

Fault protection is provided by an output overvoltage comparator and an optional short-circuit shutdown timer. The regulator current limit level is user programmable. A wide supply range allows voltages as high as 36V to be stepped down to 0.6V output.

Applications

• Notebook and Palmtop Computers, PDAs
• Digital Signal Processors
• Network Servers