LT3508

PRODUCTION

Dual Monolithic 1.4A Step-Down Switching Regulator

Data Sheet (Rev. E) Product Selection Table
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Overview

  • Wide Input Voltage Range: 3.7V to 36V
  • Two 1.4A Output Switching Regulators with Internal Power Switches
  • Adjustable 250kHz to 2.5MHz Switching Frequency
  • Synchronizable over the Full Frequency Range
  • Anti-Phase Switching Reduces Ripple
  • Uses Small Inductors and Ceramic Capacitors
  • Accurate Programmable Undervoltage Lockout
  • Independent Tracking, Soft-Start and Power Good Circuits Ease Supply Sequencing
  • Output Adjustable Down to 800mV
  • Small 4mm × 4mm 24-Pin QFN or 16-Pin Thermally Enhanced TSSOP Surface Mount Packages
  • AEC-Q100 Qualified for Automotive Applications

The LT3508 is a dual current mode PWM step-down DC/DC converter with internal power switches capable of generating two 1.4A outputs. The wide input voltage range of 3.7V to 36V makes the LT3508 suitable for regulating power from a wide variety of sources, including automotive batteries, 24V industrial supplies and unregulated wall adapters. Both converters are synchronized to a single oscillator programmable up to 2.5MHz and run with opposite phases, reducing input ripple current. Its high operating frequency allows the use of small, low cost inductors and ceramic capacitors, resulting in low, predictable output ripple. Each regulator has independent tracking and soft-start circuits and generates a power good signal when its output is in regulation, easing power supply sequencing and interfacing with microcontrollers and DSPs.

Cycle-by-cycle current limit, frequency foldback and thermal shutdown provide protection against shorted outputs, and soft-start eliminates input current surge during startup. The low current (<2µA) shutdown mode enables easy power management in battery-powered systems.

Applications

  • Automotive
  • DSP Power Supplies
  • Wall Transformer Regulation
  • DSL and Cable Modems
  • PCI Express
LT3508
Dual Monolithic 1.4A Step-Down Switching Regulator
LT3508 Application Circuit LT3508 Pin Configuration LT3508 Pin Configuration LT3508 Performance Graph
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Technical Articles 1

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Circuit Monitors 1
LTC2960
RECOMMENDED FOR NEW DESIGNS 36V Nano-Current Two-Input Voltage Monitor
Oscillators 1
LTC6909
PRODUCTION 1 to 8 Output, Multiphase Silicon Oscillator with Spread Spectrum Modulation
Power System Management (PSM) & Sequencers 1
LTC2974
RECOMMENDED FOR NEW DESIGNS 4-Channel PMBus Power System Manager Featuring Accurate Output Current Measurement
Protection Switches & Controllers 1
LTC4365
RECOMMENDED FOR NEW DESIGNS Overvoltage, Undervoltage and Reverse Supply Protection Controller
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Tools & Simulations

LTspice 1

Models for the following parts are available in LTspice:

  • LT3508
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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
DC1060A

LT3508EFE/LT3508EUF Demo Board

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Product Details

Demonstration circuit 1060 features two LT3508 step-down DC/DC switching converters. One circuit uses the LT3508EFE and the other circuit has the LT3508EUF. The LT3508 dual output step-down switching regulator has two internal power switches, a wide input voltage range, adjustable switching frequency synchronizable over the frequency range, programmable soft-start, tracking, power-good, and channel sequencing. The anti-phase switching reduces the input capacitor. The wide VIN range of the LT3508 allows step-down configurations with up to 36V input. The high power internal switches have current limit that allows for up to 1.4A output on each output.


The demonstration circuit has two circuits. The top is optimized for high efficiency, wide input range and maximum output current; the bottom is optimized for the size. The top circuit is rated for 3.3V at 1.4A and 5V at 1.4A output from a 6V–36V input using the FE package. The frequency is set to 700kHz to allow for the high VIN to VOUT ratio and provides high efficiency throughout the range. The bottom circuit generates 1.8V at 1A and 3.3V at 1A from a 5V to 16V DC input using the QFN package and shows off the compact size with 1.6MHz switching frequency.
DC1060A
LT3508EFE/LT3508EUF Demo Board
DC1060A - Schematic

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