LTC3857-1 Series

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

Catalog

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

Part	Output Phases	Control Features	Number of Outputs	Topology	Operating Temperature [Min]	Operating Temperature [Max]	Mounting Type	Supplier Device Package	Package / Case	Voltage - Supply (Vcc/Vdd) [Max]	Voltage - Supply (Vcc/Vdd) [Min]	Output Configuration	Function	Duty Cycle (Max) [Max]	Output Type	Frequency - Switching [Max]	Frequency - Switching [Min]
Analog Devices LTC3857EGN-1#TRPBF	2	Enable Frequency Control Power Good Soft Start Tracking	2	Buck	-40 °C	125 ¯C	Surface Mount	28-SSOP	28-SSOP	38 V	4 V	Positive	Step-Down	99.4 %	Transistor Driver	535 kHz 835 kHz	105 kHz 350 kHz
Analog Devices LTC3857IUH#TRPBF	2	Current Limit Enable Frequency Control Phase Control Power Good Soft Start Tracking	2	Buck	-40 °C	125 ¯C	Surface Mount	32-QFN (5x5)		38 V	4 V	Positive	Step-Down	99.4 %	Transistor Driver	535 kHz 835 kHz	105 kHz 350 kHz
Analog Devices LTC3857EGN-1#PBF	2	Enable Frequency Control Power Good Soft Start Tracking	2	Buck	-40 °C	125 ¯C	Surface Mount	28-SSOP	28-SSOP	38 V	4 V	Positive	Step-Down	99.4 %	Transistor Driver	535 kHz 835 kHz	105 kHz 350 kHz

Catalog

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

Key Features

• Low Operating IQ: 50μA (One Channel On)

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

• Wide VINRange: 4V to 38V (40V Abs Max)

• RSENSEor 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 VINor EXTVCC

• No Current Foldback During Start-up

• 5mm × 5mm QFN Package

Description

The LTC3857-1 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 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 life in battery-powered systems. The LTC3857-1 features a precision 0.8V reference and a power good output indicator. 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 operation, pulse-skipping mode, or continuous inductor current mode at light loads.For a leadless 32-pin QFN package with the additional features of adjustable current limit, clock out, phase modulation and two PGOOD outputs, see the LTC3857 data sheet.LTC3857LTC3857-1FeaturesAdjustable Current Limit, Clock Output, Phase Modulation, 2 PGOOD OutputsFixed Current Limit, One PGOOD OutputPackageQFN-32SSOP-28ApplicationsAutomotive Always-On SystemsBattery Operated Digital DevicesDistributed DC Power Systems