LTC3521

RECOMMENDED FOR NEW DESIGNS

1A Buck-Boost DC/DC and Dual 600mA Buck DC/DC Converters

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Overview

  • Three High Efficiency DC/DC Converters:
    • Buck-Boost (VOUT: 1.8V to 5.25V, IOUT: 1A)
    • Dual Buck (VOUT: 0.6V to VIN, IOUT: 600mA)
  • 1.8V to 5.5V Input Voltage Range
  • Pin-Selectable Burst Mode® Operation
  • 30μA Total Quiescent Current in Burst Mode Operation
  • Independent Power Good Indicator Outputs
  • Integrated Soft-Start
  • Thermal and Overcurrent Protection
  • <2μA Current in Shutdown
  • Small 4mm × 4mm QFN and Thermally Enhanced TSSOP Packages

The LTC3521 combines a 1A buck-boost DC/DC converter and dual 600mA synchronous buck DC/DC converters. The 1.1MHz switching frequency minimizes the solution footprint while maintaining high efficiency. All three converters feature soft-start and internal compensation to minimize the solution footprint and simplify the design process.

The buck converters are current mode controlled and utilize an internal synchronous rectifier to improve efficiency. The buck converters support 100% duty cycle operation to extend battery life. If the PWM pin is held low, the buck converters automatically transition from Burst Mode operation to PWM mode at high loads. With the PWM pin held high, the buck converters remain in low noise, 1.1MHz PWM mode.

The buck-boost converter features continuous conduction operation to maximize efficiency and minimize noise. At light loads, the buck-boost converter can be operated in Burst Mode operation to improve efficiency and reduce no-load standby current.

The LTC3521 provides a <2μA shutdown mode, overtemperature shutdown and current limit protection on all converters. The LTC3521 is available in a 24-pin 0.75mm × 4mm × 4mm QFN package, and a 20-pin thermally enhanced TSSOP package.

Applications

  • Bar Code Readers
  • Medical Instruments
  • Handy Terminals
  • PDAs, Handheld PCs
  • GPS Receivers
LTC3521
1A Buck-Boost DC/DC and Dual 600mA Buck DC/DC Converters
Efficiency vs VIN Product Package 1 Product Package 2
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Data Sheet

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Tools & Simulations

LTspice 1

Models for the following parts are available in LTspice:

  • LTC3521
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
schematic 2
schematic 3
schematic 4
DC1389A

LTC3521EUF Demo Board | Buck-Boost Plus Dual Buck, 2.4V ≤ VIN ≤ 5V, VOUT1 = 3.3V @ 0.8A, VOUT2 = 1.2V @ 0.6A, VOUT3 = 1.8V @ 0.6A

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Product Details

Demonstration circuit 1389A is high efficiency triple output DC/DC power supply featuring the LTC3521. The IC includes a 4-switch synchronous Buck-Boost DC/DC converter with a 1A switch rating and two synchronous 600mA Buck converters. The demo board accepts an input voltage between 2.4V and 5V, and provides fixed output voltages of 3.3V @800mA for the Buck-Boost converter and 1.2V & 1.8V @600mA for the Buck converters.
DC1389A
LTC3521EUF Demo Board | Buck-Boost Plus Dual Buck, 2.4V ≤ VIN ≤ 5V, VOUT1 = 3.3V @ 0.8A, VOUT2 = 1.2V @ 0.6A, VOUT3 = 1.8V @ 0.6A
DC1389A Evaluation Board DC1389A Evaluation Board - Top View DC1389A Evaluation Board - Bottom View DC1389A - Schematic

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