LT3507A

PRODUCTION

Triple Monolithic Step-Down Regulator with LDO

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Overview

  • Wide Input Range: 4V to 36V
  • One 2.7A and Two 1.8A Output Switching Regulators with Internal Power Switches
  • Low Dropout Linear Regulator with External Transistor
  • Antiphase Switching Reduces Ripple
  • Independent Run, Tracking/Soft-Start, and Power Good Indicators Ease Supply Sequencing
  • Uses Small Inductors and Ceramic Capacitors
  • Adjustable, 250kHz to 2.5MHz Switching Frequency, Synchronizable Over the Full Range
  • User Programmable Overvoltage and Undervoltage Lockouts
  • Thermally Enhanced, 38-Lead TSSOP and 5mm × 7mm QFN Packages

The LT3507A is a triple, current mode, DC/DC converter with internal power switches and a low dropout regulator. The switching converters are step-down converters capable of generating one 2.7A output and two 1.8A outputs. All three converters are synchronized to a single oscillator. The 2.7A output runs with opposite phase to the other two converters, reducing input ripple current. Each regulator has independent shutdown 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.

The switching frequency is set with a single resistor yielding a range of 250kHz to 2.5MHz. The high switching frequency allows the use of small inductors and capacitors resulting in a very small triple output supply. The constant switching frequency, combined with low impedance ceramic capacitors, results in low, predictable output ripple. Frequency foldback and thermal shutdown provide protection against fault conditions. The LT3507A provides higher output current than available with the LT3507.

Output Current Package
LT3507 2.5A, 1.5A, 1.5A 5x7 QFN-38
LT3507A 2.7A, 1.8A, 1.8A 5x7 QFN-38, TSSOP-38E

Applications

  • Automotive
  • Industrial Supplies
  • Distributed Power Regulation
  • DSP Power

LT3507A
Triple Monolithic Step-Down Regulator with LDO
5V, 3.3V, 2.5V and 1.8V Step-Down Regulator Start-Up Waveforms—Coincident Tracking Product Package 1 Product Package 2
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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
Circuit Monitors 1
LTC2960 RECOMMENDED FOR NEW DESIGNS 36V Nano-Current Two-Input Voltage Monitor
Oscillators 1
LTC6908 Resistor Set SOT-23 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
LT4363 RECOMMENDED FOR NEW DESIGNS High Voltage Surge Stopper with Current Limit
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Tools & Simulations

LTspice 1


Models for the following parts are available in LTspice:

  • LT3507
  • LT3507A
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
DC1781A

LT3507AEFE Demo Board | 7V to 36VIN, VOUT1 = 1.8V @ 2.7A, VOUT2 = 3.3V @ 1.5A, VOUT3 = 5.0V @ 1.8A, VOUT4 = 2.5V @ 0.3A

Product Details

Demo circuit 1781A is a Triple Monolithic Step-Down Regulator with LDO featuring the LT3507A. The demo circuit is designed for 1.8V, 3.3V, 5.0V and 2.5V outputs from a 7V to 36V input. The current capability of each channel is 2.7A, 1.5A, 1.8A and 0.3A respectively. Independent input voltage, feedback, soft-start and power good pins for each channel simplify complex power supply tracking/sequencing requirements.


All three converters are either synchronized to a common external clock input or single-resistor programmable from 250kHz to 2.5MHz using internal oscillator. At all frequencies, a 180° phase shift between VOUT1 and the other two outputs is maintained, reducing input voltage ripple and component size. Programmable frequency allows for optimization between efficiency and external component size.

DC1781A
LT3507AEFE Demo Board | 7V to 36VIN, VOUT1 = 1.8V @ 2.7A, VOUT2 = 3.3V @ 1.5A, VOUT3 = 5.0V @ 1.8A, VOUT4 = 2.5V @ 0.3A
DC1781A - Schematic

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