LTC3857: Low IQ, Dual, 2-Phase Synchronous Step-Down Controller Data Sheet1/12/2012441K
Features and Benefits
- 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
The LTC3857 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 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 operation, 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||Adjustable Current Limit, Clock Output, Phase Modulation, 2 PGOOD Outputs||Fixed Current Limit, One PGOOD Output|
- Automotive Always-On Systems
- Battery Operated Digital Devices
- Distributed DC Power Systems
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit 1381A is a Low Quiescent Current, Dual Output Synchronous Buck Converter featuring the LTC3857EUH/LTC3858EUH. The DC1381A provides 3.3V/5A and 8.5V/3A from a wide input voltage range of 4.5V to 36V, making it suitable for automotive or other battery fed application where low quiescent current is important.
Two versions of the board are available. DC-1381A-A is for the LTC3857EUH, while the DC1381A-B is for the LTC3858EUH. The LTC3857EUH offers lower quiescent current and smaller burst mode ripple, while the LTC3858EUH offers latch-off protection and increased burst mode efficiency.
Documentation & Resources
R526 Reliability Data3/26/2018365 K
DC1381A - Demo Manual10/22/20091M
Tools & Simulations
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Models for the following parts are available in LTspice:
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.
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LTpowerCAD Project Files
Design tools for the following parts are available in LTpowerCAD:
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 Number||Material Declaration||Reliability Data||Pin/Package Drawing||CAD Symbols, Footprints & 3D Models|
|LTC3857EUH#PBF||Material Declaration||Reliability Data||32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)|
|LTC3857EUH#TRPBF||Material Declaration||Reliability Data||32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)|
|LTC3857IUH#PBF||Material Declaration||Reliability Data||32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)|
|LTC3857IUH#TRPBF||Material Declaration||Reliability Data||32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)|
|Wafer Fabrication Data||R526 Reliability Data|
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