LTC3857-1

PRODUCTION

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

Part Models: 4
1ku List Price: Starting From $4.63

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Part Details

Low Operating I_Q: 50μA (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 Low Ripple 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
Output Overvoltage Protection
Low Shutdown I_Q: <8μA
Internal LDO Powers Gate Drive from V_IN or EXTV_CC
No Current Foldback During Start-Up
Narrow SSOP Package

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.


	LTC3857	LTC3857-1
Features	Adjustable Current Limit, Clock Output, Phase Modulation, 2 PGOOD Outputs	Fixed Current Limit, One PGOOD Output
Package	QFN-32	SSOP-28

Applications

Automotive Always-On Systems
Battery Operated Digital Devices
Distributed DC Power Systems

Part Models: 4
1ku List Price: Starting From $4.63

Documentation

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LTC3857EGN-1#PBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3857EGN-1#TRPBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3857IGN-1#PBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3857IGN-1#TRPBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Oct 3, 2024 - 24_0235 (QSOP/SSOP PKG) Migrating Bottom Trace Code Marking to Top Side Laser Marking
		PCN24_0235_Form Material_Report Other Delta Qualification Matrix
LTC3857EGN-1#PBF	PRODUCTION
LTC3857EGN-1#TRPBF	PRODUCTION
LTC3857IGN-1#PBF	PRODUCTION
LTC3857IGN-1#TRPBF	PRODUCTION
Aug 10, 2022 - 22_0177 Laser Top Mark Conversion for QSOP20_24_28 Assembled in ADPG [PNG] and UTL
		PCN22_0177_Form Material_Report Delta Qualification Matrix
LTC3857EGN-1#PBF	PRODUCTION
LTC3857EGN-1#TRPBF	PRODUCTION
LTC3857IGN-1#PBF	PRODUCTION
LTC3857IGN-1#TRPBF	PRODUCTION
Jul 31, 2020 - 20_0245 Notification of Wafer Fab Location Change for 0.6µm BICMOS Process Devices from ADI Milpitas (Hillview) to Vanguard Int. (Taiwan)
		PCN20_0245_Form Material_Report Delta Qualification Matrix Other Qualification Results Summary
LTC3857EGN-1#PBF	PRODUCTION
LTC3857EGN-1#TRPBF	PRODUCTION
LTC3857IGN-1#PBF	PRODUCTION
LTC3857IGN-1#TRPBF	PRODUCTION

This is the most up-to-date revision of the Data Sheet.

Hardware Ecosystem

Parts	Product Life Cycle	Description
Dual-Supply Monitors 1
LTC2960	RECOMMENDED FOR NEW DESIGNS	36V Nano-Current Two-Input Voltage Monitor
High Voltage Hot Swap Controllers 1
LTC4364	RECOMMENDED FOR NEW DESIGNS	Surge Stopper with Ideal Diode
Multiple Output Buck Regulators 1
LTC3880	RECOMMENDED FOR NEW DESIGNS	Dual Output PolyPhase Step-Down DC/DC Controller with Digital Power System Management
Pushbutton Controllers 1
LTC2955	RECOMMENDED FOR NEW DESIGNS	Pushbutton On/Off Controller with Automatic Turn-On

Tools & Simulations

LTspice 1

LTC3857-1 - Step-Down (Buck) Regulators

Models for the following parts are available in LTspice:

LTC3857
LTC3857-1

LTpowerCAD 1

LTC3857-1 Project - Low Iq, Dual 2-Phase Synchronous Step-Down Supply (10-36V to 3.3 @ 5A & 8.5 @ 3A)

LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

LTpowerCAD^® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.

Evaluation Kits

LTC3857EGN-1 Demo Board | Dual Output, 2-Phase, Low Iq, 4.5V ≤ VIN ≤ 36V, VOUT1 = 3.3V @ 5A, VOUT2 = 8.5V @ 3A

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Product Details

Demonstration circuit 1352A is a low quiescent current, dual output 2-phase, synchronous buck converter demo board featuring the LTC3857EGN-1 or LTC3858EGN-1. It features a 4.5V to 36V input voltage range and provides 3.3V / 5A and 8.5V / 3A outputs. Two versions of the board are available. The DC-1352A-A is for the LTC3857EGN-1, which offers lower quiescent current and smaller burst mode ripple, while the DC1352A-B is for the LTC3858EGN-1 which offers latch-off protection and increased burst mode efficiency.

Resources

DC1352A - Schematic
89.00K

DC1352A - Demo Board
1.00M

DC1352A - Design Files
3.00M

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