Power Management Switching Regulator Step-Down (Buck) Regulators Multiple Output Buck
Power Management Switching Regulator Step-Down (Buck) Regulators Internal Power Switch Buck
Power Management Switching Regulator Step-Down (Buck) Regulators High Input Voltage Buck

LT3640 - Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer

Features

  • High Voltage Buck Regulator:
    4V to 35V Operating Range
    1.3A Output Current
  • OVLO Protects Input to 55V
  • Low Voltage Synchronous Buck Regulator:
    2.5V to 5.5V Input Voltage Range
    1.1A Output Current
  • Synchronizable, Adjustable 350kHz to 2.5MHz Switching Frequency
  • Programmable Power-On Reset Timer
  • Programmable Window Mode Watchdog Timer
  • Typical Quiescent Current: 290μA
  • Short-Circuit Robust
  • Programmable Soft-Start
  • Low Shutdown Current: IQ < 1μA
  • Available in Thermally Enhanced 28-Lead
    (4mm × 5mm) QFN and 28-Lead TSSOP Packages

Typical Application

LT3640 Typical Application
LT3640 Typical Application

Description

The LT3640 is a dual channel, current mode monolithic buck switching regulator with a power-on reset and a watchdog timer. Both regulators are synchronized to a single oscillator with an adjustable frequency (350kHz to 2.5MHz). At light loads, both regulators operate in low ripple Burst Mode® to maintain high efficiency and low output ripple.

The high voltage channel is a nonsynchronous buck with an internal 2.4A top switch that operates from an input of 4V to 35V; a 36.5V OVLO protects the device to 55V. The low voltage channel operates from an input of 2.5V to 5.5V. Internal synchronous power switches provide high efficiency without the need of external Schottky diode. Both channels have cycle-by-cycle current limit, providing protection against shorted outputs.

The power-on reset and watchdog timeout periods are both adjustable using external capacitors. The window mode watchdog timer flags when the μP pulses group too close together or too far apart.

The LT3640 is available in a 28-pin 4mm × 5mm QFN package and 28-pin TSSOP package. Both packages have an exposed pad for low thermal resistance.

Packaging

For complete and up to date package information and drawings, please refer to our packaging page

QFN-28, TSSOP-28

LT3640 Package Drawing
LT3640 Package Drawing

Order Info

Package Variations and Pricing

Part Number Package Pins Temp Price (1-99) Price (1k)* RoHS Data
LT3640EFE#PBF TSSOP 28 E $5.23 $3.65 View
LT3640EFE#TRPBF TSSOP 28 E $3.71 View
LT3640EUFD#PBF QFN 28 E $5.00 $3.50 View
LT3640EUFD#TRPBF QFN 28 E $3.56 View
LT3640IFE#PBF TSSOP 28 I $5.80 $4.06 View
LT3640IFE#TRPBF TSSOP 28 I $4.12 View
LT3640IUFD#PBF QFN 28 I $5.56 $3.89 View
LT3640IUFD#TRPBF QFN 28 I $3.95 View
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* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology demo boards are offered free of charge to qualified customers. Contact your local sales office or distributor to request a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC1359A LT3640EFE Demo Board | Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer $125.00
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Applications

  • Industrial Power Supplies
  • Automotive Electronic Control Units

Simulate

LTspice IV is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. To download LTspice IV and other FREE simulation tools, please visit our Design Simulation page.

Related models available in LTspice IV
LT3640

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