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

The LTC3858-2 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 LTC3858-2 differs from the LTC3858 by having the overvoltage protection crowbar and short-circuit latchoff disabled. A wide 4V to 38V 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.

LTC3858

LTC3858-1

LTC3858-2

Features

Adjustable Current Limit, Clock Output, Phase Modulation, 2 PGOOD Outputs

Fixed Current Limit, One PGOOD Output

Overvoltage protection crowbar and short-circuit latchoff disabled

Package

QFN-32

SSOP-28

QFN-32

Applications

* Automotive Systems

* Battery Operated Digital Devices

* Distributed DC Power Systems

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

* Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V

* Wide VIN Range: 4V to 38V

* 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-850kHz)

* Programmable Fixed Frequency (50kHz-900kHz)

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

* Very Low Dropout Operation: 99% Duty Cycle

* Adjustable Output Voltage Soft-Start or Tracking

* Power Good Output Voltage Monitor

* Low Shutdown IQ: 8μA

* Internal LDO Powers Gate Drive from VIN or EXTVCC

* No Current Foldback During Start-Up

* 5mm × 5mm QFN Package