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
• Power Good Output Voltage Monitor
• Output Overvoltage Protection
• Output Latch-Off Protection During Short Circuit
• Low Shutdown I_Q: 8μA
• Internal LDO Powers Gate Drive from V_IN or EXTV_CC
• No Current Foldback During Start-Up
• Small 5mm × 5mm QFN Package

Typical Application

Description

The LTC3858 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 features a precision 0.8V reference and a power good output indicator. 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. The output latch-off feature 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 LTC3858-1 data sheet.