LTC3541

PRODUCTION

High Efficiency Buck + VLDO Regulator

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Overview

  • High Efficiency, 500mA Buck Plus 300mA VLDO™ Regulator
  • Auto Start-Up Powers Buck Output Prior to VLDO/Linear Regulator Output
  • Independent High Efficiency, 500mA Buck (VIN: 2.7V to 5.5V)
  • 300mA VLDO Regulator with 30mA Standalone Mode
  • No External Schottky Diodes Required
  • Buck Output Voltage Range: 0.8V to 5V
  • VLDO Input Voltage Range (LVIN): 0.9V to 5.5V
  • VLDO Output Voltage Range VLDO: 0.4V to 4.1V
  • Selectable Fixed Frequency, Pulse-Skip Operation or Burst Mode® Operation
  • Short-Circuit Protected
  • Current Mode Operation for Excellent Line and Load
  • Transient Response
  • Constant Frequency Operation: 2.25MHz
  • Low Dropout Buck Operation: 100% Duty Cycle
  • Small, Thermally Enhanced, 10-Lead (3mm × 3mm) DFN Package

The LTC3541 combines a synchronous buck DC/DC converter with a very low dropout linear regulator (VLDO) to provide up to two output voltages from a single input voltage with minimal external components. When configured for dual output operation, the LTC3541’s auto start-up feature will bring the Buck output into regulation in a controlled manner prior to enabling the VLDO regulator output without the need for external pin control. VLDO/linear regulator output prior to Buck output sequencing may also be obtained via external pin control. The input voltage range is ideally suited for Li-Ion battery-powered applications, as well as powering sub-3.3V logic from 5V or 3.3V rails.

The synchronous buck converter provides a high efficiency output, typically 90%, capable of providing up to 500mA of continuous output current while switching at 2.25MHz, allowing the use of small surface mount inductors and capacitors. A mode-select pin allows Burst Mode operation to be enabled for higher efficiency at light load currents, or disabled for lower noise, constant frequency operation.

The VLDO regulator provides a low noise, low voltage output capable of providing up to 300mA of continuous output current using only a 2.2μF ceramic capacitor. The input supply voltage of the VLDO regulator (LVIN) may come from the buck regulator or a separate supply.

Options Vout Switcher (V) Vout VLDO Auto Start Up Sequencing
LTC3541 Adj. down to 0.8V Adj. down to 0.4V Switcher, then VLDO
LTC3541-1 Adj. down to 0.8V Adj down to 0.4V VLDO, then switcher
LTC3541-2 1.875V fixed 1.5V fixed Switcher, then VLDO
LTC3541-3 1.8V fixed 1.575 fixed VLDO, then switcher

Applications

  • PDAs/Palmtop PCs
  • Digital Cameras
  • Cellular Phones
  • PC Cards
  • Wireless and DSL Modems
  • Other Portable Power Systems
LTC3541
High Efficiency Buck + VLDO Regulator
LTC3541 Typical Application Buck (Burst) Efficiency and Power Loss vs Load Current Product Package 1
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Data Sheet

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

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Power System Management (PSM) & Sequencers 1
LTC2974
RECOMMENDED FOR NEW DESIGNS 4-Channel PMBus Power System Manager Featuring Accurate Output Current Measurement
Switching Regulators & Controllers 1
LTC3880
RECOMMENDED FOR NEW DESIGNS Dual Output PolyPhase Step-Down DC/DC Controller with Digital Power System Management
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Tools & Simulations

LTspice 1

Models for the following parts are available in LTspice:

  • LTC3541
  • LTC3541-1
  • LTC3541-2
  • LTC3541-3
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.

Evaluation Kits

eval board
schematic 1
DC970A-A

LTC3541 Demo Board | 3V ≤ VIN ≤ 5.5V, VOUT1 (Buck) = 1.8V or 2.5V @ 500mA, VOUT2 (VLDO) = 0.8V/1.2V/1.5V/1.8V @ 300mA

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Product Details

Demonstration circuit DC970A-A and DC970A-B feature the LTC3541 and LTC3541-1 respectfully, and provide a high efficiency, synchronous buck plus VLDO linear regulator. For the LTC3541, the buck regulator powers up before the linear regular, and for the LTC3541-1, the linear regulator powers up first.


The DC970A has an input voltage range of 3.0V to 5.5V. The jumper selectable (2.5V or 1.8V) buck regulator output is capable of delivering up to 500mA of output current; the jumper selectable (0.8V, 1.2V, 1.5V or 1.8V) linear regulator output is capable of delivering up to 300mA of current.
DC970A-A
LTC3541 Demo Board | 3V ≤ VIN ≤ 5.5V, VOUT1 (Buck) = 1.8V or 2.5V @ 500mA, VOUT2 (VLDO) = 0.8V/1.2V/1.5V/1.8V @ 300mA
DC970A-A - Schematic

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