Analog Devices Inc. LT1776IS8#PBF

Overview

LT1776IS8#PBF from Analog Devices (formerly Linear Technology) is a wide-input, current-mode synchronous step-down DC/DC switching regulator IC. It accepts 7.4V–40V input, delivers up to 700mA peak switch current, operates at fixed 200kHz (synchronizable to 400kHz), and features adaptive switch drive for high-efficiency operation across light-to-heavy loads in automotive and industrial power supplies.

For engineers reviewing the LT1776IS8#PBF datasheet, LT1776IS8#PBF pinout, LT1776IS8#PBF application, or LT1776IS8#PBF equivalent, key selection criteria include its 60V transient tolerance, true current-mode control architecture, VCC-biased internal circuitry for reduced VIN quiescent draw, shutdown current of 30µA, and SO-8 package compatibility with standard PCB layouts.

Technical Context

The LT1776IS8#PBF implements true current-mode control using an internal transconductance feedback amplifier (gm = 400–1000 µmho) and a dedicated current comparator referenced to the VC pin. Its adaptive switch drive dynamically adjusts dV/dt-high slew rate under medium/heavy loads for efficiency, reduced slew under light loads to avoid pulse skipping.

It integrates oscillator, bias regulation (dual VIN/VCC inputs), protection logic, and a 700mA peak-rated NPN output switch. The internal oscillator synchronizes externally via SYNC pin (1.5–2.2V threshold, 250–400kHz range) and automatically slows to ~30kHz during short-circuit conditions when FB voltage drops below ~0.83V, preserving cycle-by-cycle current limiting.

Key Specifications

Pinout & Package

LT1776IS8#PBF is housed in an 8-lead plastic SOIC (SO-8) package with standard JEDEC MS-012AC footprint (5.0mm × 4.0mm, 1.27mm pitch). Thermal resistance θ_JA = 110°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with LT1776IS8#PBF, LTC3631EMSE#PBF offers higher current and efficiency but sacrifices synchronization and transient robustness, while TPS54202DRCT provides greater integration and lower IQ but cannot withstand 40V+ inputs or deliver current-mode fault protection.

Availability

LT1776IS8#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial sensor nodes, and IEEE 1394 power supplies requiring stable component supply, extended temperature support (–40°C to 125°C), and 60V transient tolerance.

Supply support for LT1776IS8#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.

The LT1776IS8#PBF belongs to ADI's legacy Linear Technology power management portfolio, designed specifically for rugged, wide-input-voltage DC/DC conversion in automotive, industrial, and communications infrastructure where reliability under voltage transients is critical.

FAQ

What is the absolute maximum input voltage rating for the LT1776IS8#PBF?

The LT1776IS8#PBF has an absolute maximum input voltage rating of 60V on both VIN and VSW pins, verified per Absolute Maximum Ratings table. However, continuous operation above 40V is thermally limited and depends on output current, switching frequency, and PCB copper area. For sustained 40V operation at full load, ensure θ_JA ≤ 110°C/W and ambient ≤ 85°C.

Does the LT1776IS8#PBF support synchronization to an external clock source?

Yes, the LT1776IS8#PBF supports external synchronization via the SYNC pin (Pin 6). It accepts logic-level signals (10–90% duty cycle) and locks to frequencies from 250kHz to 400kHz. The internal oscillator automatically disables sync functionality when FB voltage drops below ~0.83V, ensuring reliable short-circuit protection remains active.

What is the purpose of the VCC pin on the LT1776IS8#PBF, and how should it be connected?

The VCC pin (Pin 2) powers the LT1776IS8#PBF's internal control circuitry from the regulated output rail instead of VIN, reducing quiescent current drawn from the high-voltage input. It must be connected directly to the output capacitor's positive terminal. If routing exceeds 1 inch, add a 0.1µF ceramic capacitor from VCC to GND at the IC pin to ensure stable bias under dynamic load.

How does the LT1776IS8#PBF handle short-circuit conditions on its output?

The LT1776IS8#PBF responds to output short circuits by monitoring the FB pin voltage. When FB falls below ~0.83V, the internal oscillator slows linearly from 200kHz down to ~30kHz. This increases minimum on-time margin, preserving current-mode control and preventing uncontrolled current ramp-up while maintaining cycle-by-cycle limiting via the VC clamp at 2.0V.

Can the LT1776IS8#PBF operate with an input voltage below 7.4V?

No - the LT1776IS8#PBF has a guaranteed minimum operating input voltage of 7.4V (typ. 7.0V, min. 6.7V). Below this, internal bias circuitry cannot sustain regulation, and the part may fail to start or drop out of regulation. For sub-7V applications, consider alternatives such as the LT3971 or LTC3642, which support lower VIN thresholds.