Features

• Low Operating I_Q: 170μA (One Channel On)
• Wide Output Voltage Range: 0.8V ≤ V_OUT ≤ 24V
• Wide V_IN Range: 4V to 38V
• R_SENSE or DCR Current Sensing
• Out-of-Phase Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
• OPTI-LOOP® Compensation Minimizes C_OUT
• 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 I_Q: 8μA
• Internal LDO Powers Gate Drive from V_IN or EXTV_CC
• No Current Foldback During Start-Up
• 5mm × 5mm QFN Package

Typical Application

Description

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.