Analog Devices Inc. LT1767EMS8-3.3#PBF

Overview

LT1767EMS8-3.3#PBF from Analog Devices (formerly Linear Technology) is a monolithic 1.25MHz, 1.5A synchronous step-down switching regulator in an 8-pin MSOP package with exposed pad option, featuring fixed 3.3V output, 0.22Ω internal NPN switch, 2% output tolerance, and operation from 3V to 25V input. It delivers up to 1.2A at 3.3V in typical DSL modem and portable computer power rails.

For engineers reviewing the LT1767EMS8-3.3#PBF datasheet, LT1767EMS8-3.3#PBF pinout, LT1767EMS8-3.3#PBF application, or LT1767EMS8-3.3#PBF equivalent, key selection criteria include verified 3.3V fixed-output accuracy, thermal performance of the MS8E package (θ_JA = 40°C/W), current-mode control for transient response, and synchronization capability up to 2MHz.

Technical Context

The LT1767EMS8-3.3#PBF implements constant-frequency current-mode control with cycle-by-cycle peak current limiting and internal 1.25MHz oscillator. Its bipolar NPN power switch is driven via BOOST pin to achieve low 330mV typical on-voltage drop at –1.5A.

Feedback uses a precision 1.2V reference internally scaled for fixed 3.3V output (3.234V–3.366V over temperature), and shutdown is controlled by a 1.33V threshold SHDN pin with 7µA hysteresis current, enabling accurate undervoltage lockout implementation.

Key Specifications

Pinout & Package

LT1767EMS8-3.3#PBF is packaged in an 8-lead plastic MSOP (MS8) with exposed thermal pad (MS8E variant also available). The MS8E package features GND-connected exposed pad soldered to large copper area for optimal thermal dissipation (θ_JA = 40°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck regulator applications.

Compared with LT1767EMS8-3.3#PBF, LTC3605EMS8E-3.3#PBF offers higher frequency and integration but lower current rating, while TPS54331DR provides adjustable output and higher current but lacks thermal performance and fixed-voltage simplicity.

Availability

LT1767EMS8-3.3#PBF is available at Aetrix Electronics and suitable for DSL modems, portable computers, and wall adapters requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for LT1767EMS8-3.3#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LT1767 family.

The LT1767 product line was designed specifically for high-efficiency, high-frequency DC/DC conversion in space- and thermally-constrained applications such as networking infrastructure, portable computing, and industrial power supplies.

FAQ

What is the maximum continuous output current of the LT1767EMS8-3.3#PBF?

The LT1767EMS8-3.3#PBF delivers up to 1.2A continuously under typical conditions (12V input → 3.3V output) with proper PCB thermal design. Its 1.5A minimum switch current limit and thermal derating curve allow this output level when using the MS8E exposed-pad package with ≥2 cm² copper area. At elevated ambient temperatures or with MS8 (non-exposed) packaging, output current must be reduced per the thermal derating graph in the datasheet.

Does the LT1767EMS8-3.3#PBF require external feedback resistors?

No, the LT1767EMS8-3.3#PBF does not require external feedback resistors. As a fixed-output variant, it integrates the resistor divider internally and connects the FB pin directly to the 3.3V output. This eliminates component count, layout sensitivity, and tolerance errors associated with external dividers - a key advantage over adjustable regulators like the LT1767 (adj) version.

Can the LT1767EMS8-3.3#PBF be synchronized to an external clock?

Yes, the LT1767EMS8-3.3#PBF supports external synchronization via its SYNC pin, accepting logic-level signals from 1.5MHz to 2MHz. When synchronized, the internal oscillator locks to the external frequency, enabling EMI reduction through frequency alignment or dithering. If unused, the SYNC pin must be grounded to prevent noise coupling.

What is the purpose of the BOOST pin on the LT1767EMS8-3.3#PBF?

The BOOST pin on the LT1767EMS8-3.3#PBF supplies a voltage higher than VIN to the base drive of the internal NPN switch, ensuring saturation and minimizing on-state voltage drop to ~330mV. It requires an external 0.1µF capacitor and Schottky diode (e.g., CMDSH-3), typically tied to the output. Without BOOST, switch losses increase significantly, degrading efficiency and thermal performance.

How does the LT1767EMS8-3.3#PBF handle thermal overload?

The LT1767EMS8-3.3#PBF incorporates thermal shutdown that disables the regulator when junction temperature exceeds 125°C. Recovery occurs automatically once temperature falls below the hysteresis threshold (~115°C). Combined with full-cycle current limiting and the low θ_JA of the MS8E package, this protects the device during sustained overload or poor PCB heat sinking - a critical safeguard in unattended embedded systems.