LTC3446

PRODUCTION

Monolithic Buck Regulator with Dual VLDO Regulators

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Overview

  • High Efficiency Triple Step-Down Outputs from a Single Input Supply
  • 1A Synchronous Buck Regulator Provides Main Step-Down Output and Powers Two 300mA VLDO™ Linear Regulators
  • Output Voltages as Low as 400mV (VLDO Outputs)
  • Power Good Output
  • Input Voltage Range: 2.7V to 5.5V
  • Independent Internal Soft-Start for Each Supply
  • Independent Enable Pin for Each Supply
  • Low (140µA Typ) No-Load Quiescent Current with All Outputs Enabled
  • Constant Frequency Current Mode Operation
  • 2.25MHz Switching Frequency Uses Small Inductors
  • Defeatable Automatic Burst Mode® Operation for High Efficiency at Light Loads
  • ±1.5% Reference Accuracy
  • Overtemperature Protection
  • Thermally Enhanced 4mm × 3mm 14-Pin DFN Package

The LTC3446 combines a synchronous buck DC/DC converter with two very low dropout (VLDO) linear regulators to provide up to three stepped-down output voltages from a single input voltage. The input voltage range is ideally suited for Li-Ion battery-powered applications, as well as powering low voltage logic from 5V or 3.3V rails. The output voltage range extends down to 0.4V for the VLDO regulators and 0.8V for the buck.

The 1A synchronous buck converter provides the main output with high efficiency, typically 85%. The two 300mA VLDO regulators can run off the main output to provide two additional lower voltage outputs. A built-in supply monitor provides a power good indication.

The buck converter switches at 2.25MHz, allowing the use of small surface mount inductors and capacitors. Constant frequency current mode operation produces controlled output spectrum and fast transient response. A mode-select pin allows automatic Burst Mode operation to be enabled for higher efficiency at light load, or disabled for lower noise operation down to very light loads. The two VLDO regulators are stable with ceramic output capacitors as small as 1µF.

Applications

  • Low Power Handheld Devices
  • Low Voltage and Multivoltage Power for Digital Logic, I/O, FPGAs, CPLDs, ASICs and CPUs
LTC3446
Monolithic Buck Regulator with Dual VLDO Regulators
Buck Efficiency vs Buck Load Current Product Package 1
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Design Note 2

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

Models for the following parts are available in LTspice:

  • LTC3446
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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
DC893A

LTC3446EDE Demo Board | 2.9V ≤ VIN ≤ 5.5V, VOUT1 = 1.8V @ 400mA, VOUT2/VOUT3 = 1.2V/1.5V @ 300mA

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Product Details

Demonstration circuit 893A is a triple output converter using the LTC3446 1A monolithic synchronous buck regulator with dual 300mA very low drop-out linear regulators (VLDOs). The DC893A has an input voltage range of 2.9V to 5.5V, and is capable of delivering up to 400mA of load current on the buck output and up to 300mA on each VLDO output. The buck regulator output voltage of the DC893A can be set as low as 0.8V, and the dual VLDOs can be set as low as 0.4V.
DC893A
LTC3446EDE Demo Board | 2.9V ≤ VIN ≤ 5.5V, VOUT1 = 1.8V @ 400mA, VOUT2/VOUT3 = 1.2V/1.5V @ 300mA
DC893A - Schematic

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