Analog Devices Inc. LT1506CR-3.3SYNC#TRPBF

Overview

LT1506CR-3.3SYNC#TRPBF from Analog Devices (formerly Linear Technology) is a 4.5A, 500kHz fixed-output 3.3V monolithic synchronous step-down switching regulator in SO-8 package with SYNC pin for external clock synchronization and optimized for 4V–15V input operation. It integrates a saturated NPN power switch (0.07Ω typical R_DS(on) equivalent), current-mode control, cycle-by-cycle current limiting, and thermal shutdown - used in portable computers and battery-powered systems requiring compact, efficient DC/DC conversion.

For engineers reviewing the LT1506CR-3.3SYNC#TRPBF datasheet, LT1506CR-3.3SYNC#TRPBF pinout, LT1506CR-3.3SYNC#TRPBF application, or LT1506CR-3.3SYNC#TRPBF equivalent, key selection criteria include confirmed 3.3V fixed output accuracy (±1.5%), 500kHz nominal switching frequency with 580kHz–1MHz sync range, 4.5A peak switch current limit, 20µA shutdown current, and SO-8 thermal performance (θ_JA = 80°C/W).

Technical Context

The LT1506CR-3.3SYNC#TRPBF implements constant-frequency current-mode control using an internal 500kHz oscillator and cycle-by-cycle peak current sensing via the SENSE pin. Its bipolar NPN switch is driven by a BOOST pin voltage (≥VIN + 2.3V) to achieve saturation and low conduction loss.

Synchronization replaces the SHDN function: the SYNC pin accepts logic-level signals (10%–90% duty cycle) to lock the oscillator from 580kHz up to 1MHz, enabling EMI reduction and multi-regulator phase alignment. The SENSE pin directly monitors the 3.3V output (not FB), with 3.25V–3.35V tolerance at 25°C and ±0.02V/°C drift.

Key Specifications

Pinout & Package

LT1506CR-3.3SYNC#TRPBF is housed in an 8-lead plastic SO package (SO-8) with fused GND pin connected to internal tab for enhanced thermal dissipation. Pin 1 is VIN; Pin 2 is BOOST; Pin 3 is GND (fused, thermally tied to tab); Pin 4 is VSW; Pin 5 is SYNC; Pin 6 is VC; Pin 7 is SENSE; Pin 8 is NC (no connect).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3605EDE-3.3#TRPBF and TPS54331DR, the LT1506CR-3.3SYNC#TRPBF uniquely combines wide 4–15V input support, true fixed 3.3V SENSE interface, and logic-level SYNC capability in SO-8 - making it irreplaceable for legacy industrial and portable designs requiring robust, low-component-count 4.5A conversion.

Availability

LT1506CR-3.3SYNC#TRPBF is available at Aetrix Electronics and suitable for portable computers, battery-powered systems, and distributed power architectures requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LT1506CR-3.3SYNC#TRPBF 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 technical and manufacturing continuity for the LT® product family. Linear pioneered high-performance analog ICs with emphasis on precision power management and signal conditioning.

The LT1506 series was designed specifically for high-efficiency, wide-input-range DC/DC conversion in space- and thermal-constrained portable and industrial equipment - emphasizing monolithic integration, thermal robustness, and EMI-controllable switching.

FAQ

What is the guaranteed output voltage tolerance for LT1506CR-3.3SYNC#TRPBF over temperature and line/load conditions?

The LT1506CR-3.3SYNC#TRPBF guarantees 3.3V output within ±1.5% (3.25V to 3.35V) at 25°C under all line and load conditions. Over the full operating junction temperature range (0°C to 125°C), total variation remains within ±2.5% due to ±0.02V/°C drift. This is specified in the Electrical Characteristics table under "Sense Voltage (Fixed 3.3V)" with min/typ/max columns.

Can LT1506CR-3.3SYNC#TRPBF operate with a 4.0V input and still regulate 3.3V at full 4.5A load?

Yes - the LT1506CR-3.3SYNC#TRPBF has a guaranteed minimum input voltage of 4.0V (Note 3), and Figure 13 ("Maximum Load Current at VOUT = 3.3V") confirms ≥3.8A output at VIN = 4.0V with L = 1.8µH. Full 4.5A is achievable above VIN ≈ 4.3V. Efficiency drops to ~82% at 4.0V/3.8A due to reduced duty cycle and higher conduction losses.

What external components are mandatory for basic operation of LT1506CR-3.3SYNC#TRPBF?

Mandatory components are: (1) BOOST capacitor (10nF ceramic) and Schottky diode (e.g., MBRS330T3) between VIN and BOOST; (2) catch diode (e.g., MBRS330T3) from VSW to GND; (3) output inductor (1.8–10µH, rated ≥5A DC); (4) output capacitor (100µF solid tantalum, ESR ≤0.1Ω). No feedback resistors are needed - the SENSE pin connects directly to the 3.3V rail.

How does the SYNC pin function differ from the SHDN pin in LT1506CR-3.3SYNC#TRPBF compared to non-SYNC variants?

In LT1506CR-3.3SYNC#TRPBF, the SYNC pin replaces SHDN entirely - Pin 5 is SYNC (not SHDN), and there is no shutdown capability. The SYNC pin accepts logic-level inputs (1.5–2.2V threshold) to synchronize the internal oscillator from 580kHz to 1MHz. Non-SYNC versions (e.g., LT1506CR-3.3#TRPBF) retain SHDN on Pin 5 for micropower disable (20µA I_Q).

Is thermal derating required for LT1506CR-3.3SYNC#TRPBF when operating at 4.5A continuous current?

Yes - the SO-8 package has θ_JA = 80°C/W. At 4.5A/3.3V (14.85W output), assuming 88% efficiency (1.68W dissipation), junction rise is ~134°C above ambient. To stay within 125°C T_J(max), ambient must be ≤−9°C unless thermal relief is added. Use of the fused GND pad on a 1-in² copper area reduces θ_JA to ~30°C/W, enabling full 4.5A at 70°C ambient.