LT3688

PRODUCTION

Dual 800mA Step-Down Switching Regulator with Power-On Reset and Watchdog Timer

Part Models: 10
1ku List Price: Starting From $4.31

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Overview

Wide Input Range:
- Operation from 3.8V to 36V
Low Ripple (<25mV_P-P ) Burst Mode Operation:
- I_Q = 115μA at 12V_IN to 3.3V and 5V
Programmable, Defeatable Window Watchdog Timer
Two Independently Programmable Power-On-Reset Timers
Synchronizable, Adjustable 350kHz-2.2MHz Switching Frequency
Two 800mA Output Switching Regulators with Internal Power Switches
Programmable Input Undervoltage Lockout with Hysteresis
Thermally Enhanced 24-Pin TSSOP and 4mm × 4mm QFN Packages

The LT3688 is an adjustable frequency (350kHz to 2.2MHz) dual monolithic step-down switching regulator with two power-on reset timers and a watchdog timer. The regulator operates off inputs up to 36V. Low ripple Burst Mode^® operation maintains high efficiency at low output current while keeping output ripple below 25mV in a typical application, with input quiescent current of just 115μA. Shutdown circuitry reduces input supply current to less than 1μA while EN/UVLO is pulled low.

The reset and watchdog timeout periods are both adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation without false triggering. The open collector RST pins will pull down if the monitored output voltage drops 10% below the programmed value. The LT3688 watchdog timer monitors for watchdog falling edges grouped too close together or too far apart.

The LT3688 is available in 24-Pin TSSOP and 4mm × 4mm QFN packages, each with an exposed pad for low thermal resistance.

Applications

Automotive Electronic Control Units
Industrial Power Supplies
High-Reliability μProcessor Systems

Part Models: 10
1ku List Price: Starting From $4.31

Documentation

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LT3688EFE#PBF	24-Lead TSSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688EFE#TRPBF	24-Lead TSSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688EUF#PBF	24-Lead QFN (4mm x 4mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688EUF#TRPBF	24-Lead QFN (4mm x 4mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688HFE#PBF	24-Lead TSSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688HFE#TRPBF	24-Lead TSSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688IFE#PBF	24-Lead TSSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688IFE#TRPBF	24-Lead TSSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688IUF#PBF	24-Lead QFN (4mm x 4mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3688IUF#TRPBF	24-Lead QFN (4mm x 4mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Apr 6, 2022 - 22_0068 Laser Top Mark for ETSSOP and TSSOP Packages Assembled in ADPG [PNG] and UTL
		PCN22_0068_Form Material_Report Delta Qualification Matrix
LT3688EFE#PBF	PRODUCTION
LT3688EFE#TRPBF	PRODUCTION
LT3688HFE#PBF	PRODUCTION
LT3688HFE#TRPBF	PRODUCTION
LT3688IFE#PBF	PRODUCTION
LT3688IFE#TRPBF	PRODUCTION
Feb 20, 2022 - 21_0269 Addition of Alternate Assembly Site ASE Taiwan for Select LFCSP Products
		PCN21_0269_Form Material_Report Detailed Change Description Qualification Results Summary
LT3688EUF#PBF	PRODUCTION
LT3688EUF#TRPBF	PRODUCTION
LT3688IUF#PBF	PRODUCTION
LT3688IUF#TRPBF	PRODUCTION

This is the most up-to-date revision of the Data Sheet.

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
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 2
LTC4364	RECOMMENDED FOR NEW DESIGNS	Surge Stopper with Ideal Diode
LTC4365	RECOMMENDED FOR NEW DESIGNS	Overvoltage, Undervoltage and Reverse Supply Protection Controller

Tools & Simulations

LTspice 1

LT3688 Demo Circuit - Dual 800mA Step-Down Switching Regulator with POR and WDT (12V to 5V @ 800mA)

Models for the following parts are available in LTspice:

LT3688

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

LT3688EFE Demo Board | 7V ≤ VIN ≤ 36V, 60V Transients, VOUT1 = 5V @ 0.8A, VOUT2 = 3.3V @ 0.8A

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Product Details

Demonstration circuit 1439A is an adjustable dual monolithic step-down switching regulator with two adjustable power-on reset timers and an adjustable watchdog timer. The regulator operates off inputs up to 36V and withstands transients up to 60V. The two buck outputs are capable of generating up to 800mA each and both of them have independent RUN/SS function.

Resources

DC1439A - Schematic
4/4/2011

DC1439A - Demo Manual
3/25/2011

DC1439A - Design Files
4/4/2011

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