LTC3728L-1

PRODUCTION

Dual, 550kHz, 2-Phase Synchronous Regulator

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Overview

  • Dual, 180° Phased Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
  • OPTI-LOOP® Compensation Minimizes COUT
  • ±1.5% Output Voltage Accuracy
  • Power Good Output Voltage Indicator
  • Phase-Lockable Fixed Frequency 250kHz to 550kHz
  • Over Current Latch-off Disabled
  • Wide VIN Range: 4.5V to 28V (35V for LTC3728LI-1) Operation
  • Very Low Dropout Operation: 99% Duty Cycle
  • Adjustable Soft-Start Current Ramping
  • Foldback Output Current Limiting
  • Output Overvoltage Protection
  • Low Shutdown IQ: 20μA
  • 5V and 3.3V Standby Regulators
  • 3 Selectable Operating Modes: Constant Frequency, Burst Mode® Operation and PWM
  • 5mm × 5mm QFN and 28-Lead Narrow SSOP Packages

The LTC3728L-1 is a dual high performance step-down switching regulator controller that drives all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows phase-lockable frequency of up to 550kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase. The LTC3728L-1 is identical to the LTC3728L except that the LTC3728L-1 lacks the over current latch-off feature.

OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The precision 0.8V reference and power good output indicator are compatible with future microprocessor generations, and a wide 4.5V to 28V (30V maximum/35V for LTC3728LI-1) input supply range encompasses all battery chemistries.

A RUN/SS pin for each controller provides soft-start. Current foldback limits MOSFET dissipation during shortcircuit conditions. The FCB mode pin can select among Burst Mode operation, constant frequency mode and continuous inductor current mode or regulate a secondary winding. The LTC3728L-1 includes a power good output pin that indicates when both outputs are within 7.5% of their designed set point.

VIN Range VREF Accy Current Limit Latch Off 3.3V LDO Available
LTC3728 3.5V to 36V ±1% Yes
LTC3728L 4.5V to 28V ±1% Yes Yes
LTC3728LX 4.5V to 28V ±1.5% Yes Yes
LTC3728L-1 4.5V to 28V ±1.5% Foldback only Yes

Applications

  • Notebook and Palmtop Computers
  • Telecom Systems
  • Portable Instruments
  • Battery-Operated Digital Devices
  • DC Power Distribution Systems
LTC3728L-1
Dual, 550kHz, 2-Phase Synchronous Regulator
Figure 1. High Efficiency Dual 5V/3.3V Step-Down Converter Product Package 1 Product Package 2
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Documentation

Data Sheet 1

Reliability Data 1

Design Note 1

Data Sheet

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Software Resources

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Hardware Ecosystem

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Tools & Simulations

LTspice

Models for the following parts are available in LTspice:

  • LTC3728
  • LTC3728L
LTspice

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.

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