Low I, Dual 2-Phase Synchronous Step-Down Controller

The LTC3868 is a high performance dual step-down switching regulator controller that drives all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows a phase-lockable frequency of up to 850kHz. Power loss and noise due to the input capacitor ESR are minimized by operating the two controller outputs out of phase.

The 170μA no-load quiescent current extends operating life in battery-powered systems. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3868 features a precision 0.8V reference and a power good output indicator. A wide 4V to 24V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries.

Independent soft-start pins for each controller ramp the output voltages during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The output short-circuit latchoff feature further protects the circuit in short-circuit conditions.

For a leaded 28-lead SSOP package with a fixed current limit and one PGOOD output, without phase modulation or a clock output, see the LTC3868-1 data sheet.

LTC3868

LTC3868-1

Features

Adjustable Current Limit, Clock Out Pin, Phase Modulation, Two PGOOD

Fixed Current Limit, One PGOOD

Package

QFN-32

SSOP-28

Applications

* Notebook and Palmtop Computers

* Portable Instruments

* Battery Operated Digital Devices

* Distributed DC Power Systems

* Low Operating IQ: 170μA (One Channel On)

* Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 14V

* Wide VIN Range: 4V to 24V

* RSENSE or DCR Current Sensing

* Out-of-Phase Controllers Reduce Required Input Capacitance and Power Supply Induced Noise

* OPTI-LOOP® Compensation Minimizes COUT

* Phase-Lockable Frequency (75kHz to 850kHz)

* Programmable Fixed Frequency (50kHz to 900kHz)

* Selectable Continuous, Pulse-Skipping or Burst Mode® Operation at Light Loads