LTC3857EUH
DESCRIPTION
The LTC®3857 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 fre-quency of up to 850kHz. Power loss and noise due to the ESR of the input capacitor ESR are minimized by operating the two controller output stages out of phase.
The 50μA no-load quiescent current extends operating run time in battery-powered systems. The LTC3857 features a precision 0.8V reference and power good output indicators. A wide 4V to 38V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries.
Independent TRACK/SS pins for each controller ramp the output voltages during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The PLLIN/MODE pin selects among Burst Mode opera-tion, pulse-skipping mode, or continuous inductor current mode at light loads.
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 LTC3857-1 data sheet.
FEATURES
Low Operating IQ: 50μA One Channel On
Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
Wide VIN Range: 4V to 38V 40V Abs Max
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 Low Ripple Burst Mode®
Operation at Light Loads
Selectable Current Limit
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Power Good Output Voltage Monitors
Output Overvoltage Protection
Low Shutdown IQ : <8μA
Internal LDO Powers Gate Drive from VIN or EXTVCC
No Current Foldback During Start-up
5mm × 5mm QFN Package
APPLICATIONS
Automotive Always-On Systems
Battery Operated Digital Devices
Distributed DC Power Systems
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