Analog Devices Inc. LT1506CR-SYNC#PBF

Overview

LT1506CR-SYNC#PBF from Analog Devices (formerly Linear Technology) is a 4.5A, 500kHz monolithic synchronous step-down switching regulator with integrated NPN power switch, optimized for 4V–15V input and fixed 3.3V output. It features cycle-by-cycle current limiting, thermal shutdown, and synchronization capability via the SYNC pin. Used in portable computers and battery-powered systems requiring compact, efficient DC/DC conversion.

For engineers reviewing the LT1506CR-SYNC#PBF datasheet, LT1506CR-SYNC#PBF pinout, LT1506CR-SYNC#PBF application, or LT1506CR-SYNC#PBF equivalent, key selection considerations include its 500kHz constant-frequency current-mode architecture, 0.07Ω switch on-resistance, 20µA shutdown current, SYNC-enabled frequency locking up to 1MHz, and SO-8 fused-lead package compatibility with surface-mount designs.

Technical Context

The LT1506CR-SYNC#PBF implements a current-mode buck topology with internal 500kHz oscillator, error amplifier (2000 µMho transconductance), and slope compensation to prevent subharmonic oscillation. Its BOOST pin enables saturation of the on-die NPN switch, reducing conduction loss to that of a 0.07Ω FET while maintaining small die area.

Synchronization is achieved via logic-level compatible SYNC pin (1.5–2.2V threshold), allowing external clock alignment from 580kHz to 1MHz. The device replaces SHDN functionality with SYNC in this variant, and uses SENSE pin (not FB) for fixed 3.3V regulation with ±1.5% output tolerance over temperature and line.

Key Specifications

Pinout & Package

The LT1506CR-SYNC#PBF is housed in an 8-lead plastic SO package with fused ground pin (GND connected directly to internal tab). Thermal resistance θ_JA = 80°C/W with standard PCB layout; improved to ~30°C/W with large copper area under tab.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3866EMSE#PBF and TPS54332DR, the LT1506CR-SYNC#PBF offers unique integration of a saturated NPN switch with SYNC capability in a compact SO-8 package - ideal for space-constrained 4.5A applications needing deterministic EMI control without external drivers or complex compensation.

Availability

LT1506CR-SYNC#PBF is available at Aetrix Electronics and suitable for portable computers, battery-powered systems, and distributed power architectures requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production lots.

Supply support for LT1506CR-SYNC#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 the LT® series.

The LT1506 belongs to Linear's monolithic buck regulator family designed specifically for high-efficiency, low-input-voltage DC/DC conversion in portable and battery-operated equipment - emphasizing integration, thermal robustness, and EMI controllability.

FAQ

What is the function of the SYNC pin on the LT1506CR-SYNC#PBF?

The SYNC pin on the LT1506CR-SYNC#PBF replaces the SHDN pin found on non-SYNC variants and accepts an external logic-level clock signal (10–90% duty cycle) to synchronize the internal 500kHz oscillator. It operates within a 580kHz–1MHz range and must be grounded when unused. This feature prevents beat frequencies in multi-rail systems and enables precise EMI timing control - a key differentiator of the LT1506CR-SYNC#PBF versus standard adjustable versions.

Does the LT1506CR-SYNC#PBF require an external feedback resistor network?

No. The LT1506CR-SYNC#PBF is the fixed 3.3V output variant and uses the SENSE pin instead of FB. Internal precision resistors set the output to 3.3V ±1.5%, eliminating the need for external dividers. This simplifies layout, improves accuracy over temperature, and removes sensitivity to FB pin bias current - a verified design characteristic confirmed in the Electrical Characteristics table and Pin Functions section of the official datasheet.

What is the maximum continuous output current achievable with the LT1506CR-SYNC#PBF?

The LT1506CR-SYNC#PBF delivers up to 4.5A peak switch current at ≤50% duty cycle, but maximum continuous output current depends on input voltage, inductor value, and thermal conditions. For example, at VIN = 5V and VOUT = 3.3V (66% duty cycle), peak switch current drops to ~4.3A, and continuous output is ~3.7A with a 3.3µH inductor. Derating applies above 85°C ambient; full 4.5A is sustainable only with adequate copper area and airflow per the thermal data in the Package/Order Information section.

How does the BOOST pin improve efficiency in the LT1506CR-SYNC#PBF?

The BOOST pin on the LT1506CR-SYNC#PBF supplies a voltage higher than VIN to the base drive of the internal NPN switch, enabling deep saturation and reducing effective on-resistance to 0.07Ω. This cuts conduction loss significantly versus conventional bipolar designs - improving efficiency from ~75% to >89% at 4.5A. The BOOST capacitor and external diode form a charge pump; proper placement (short traces, low-ESR ceramic) is critical to maintain this benefit, as specified in the Applications Information section.

Is thermal shutdown active in the LT1506CR-SYNC#PBF, and how is it implemented?

Yes, thermal shutdown is fully implemented in the LT1506CR-SYNC#PBF and activates at junction temperature ≥125°C. It is independent of other protections and forces complete shutdown until TJ falls below ~115°C hysteresis. The fused GND pin in the SO-8 package provides direct thermal path to PCB copper; datasheet-specified θ_JA = 80°C/W assumes minimal copper, while θ_JA ≈ 30°C/W is achievable with 0.5 in² ground plane - both values validated in the Absolute Maximum Ratings and Package/Order Information sections.