Analog Devices Inc. LT1576CS8

Overview

LT1576CS8 from Analog Devices (formerly Linear Technology) is a 200kHz monolithic step-down switching regulator with integrated 1.5A NPN power switch, 1.21V reference, and fused-lead SO-8 package. It delivers up to 1.25A at fixed 5V output or adjustable down to 1.2V, supports synchronization via SYNC pin, and targets battery-powered systems requiring high efficiency and low EMI.

For engineers reviewing the LT1576CS8 datasheet, LT1576CS8 pinout, LT1576CS8 application, or LT1576CS8 equivalent, key selection criteria include its 200kHz constant-frequency current-mode control, 0.2Ω typical switch on-resistance, fused ground lead for thermal performance, shutdown/synchronization dual-function pin option, and compatibility with standard surface-mount inductors and capacitors.

Technical Context

The LT1576CS8 implements current-mode control with cycle-by-cycle peak current limiting and internal slope compensation to prevent subharmonic oscillation. Its oscillator operates at a fixed 200kHz (±20kHz over temperature), with line regulation of 0.15%/V and frequency foldback triggered below 0.7V on FB/SENSE.

It uses a bipolar NPN switch driven by an external BOOST capacitor to achieve saturation, reducing conduction loss versus conventional bipolar designs. The fused SO-8 ground lead lowers θ_JA to 80°C/W when connected to a ground plane, enabling operation up to 125°C junction temperature.

Key Specifications

Pinout & Package

LT1576CS8 is housed in an 8-lead plastic SOIC (SO-8) package with fused ground lead for enhanced thermal performance. Pin 4 (GND) must be connected directly to a low-impedance ground plane to minimize noise coupling and ensure stable regulation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3605EDE and LM2678SD-5.0, the LT1576CS8 uniquely balances 200kHz switching, fused-lead thermal performance, and analog-friendly current-mode control-making it optimal for portable, battery-fed systems needing robust fault handling and predictable EMI behavior without sacrificing efficiency.

Availability

LT1576CS8 is available at Aetrix Electronics and suitable for portable computers, battery-powered instrumentation, and distributed power nodes requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LT1576CS8 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 its portfolio of high-performance analog and power management ICs.

The LT1576 product line was designed specifically for noise-sensitive, battery-operated DC/DC conversion-emphasizing low EMI, thermal robustness in compact packages, and intelligent fault protection like frequency and current foldback.

FAQ

What is the difference between LT1576CS8 and LT1576CS8-SYNC?

The LT1576CS8-SYNC variant replaces the SHDN (shutdown) function on Pin 8 with SYNC (synchronization) capability, allowing the internal 200kHz oscillator to lock to an external clock signal between 250–400kHz. The standard LT1576CS8 retains SHDN functionality on Pin 8 for micropower disable. Both share identical electrical specs, package, and thermal performance-only the Pin 8 function differs.

Can LT1576CS8 operate with input voltage below 6V?

No. The LT1576CS8 has a minimum specified input voltage of 6V per Absolute Maximum Ratings and Electrical Characteristics tables. Operation below 6V is not guaranteed-the internal bias regulator fails to maintain reference stability and oscillator frequency, causing unregulated output or startup failure. For sub-6V inputs, consider the LT1576-5 variant with BIAS pin tied to ≥3.3V output, but even then, minimum running voltage remains 5.0V (guaranteed).

How does the fused ground lead on LT1576CS8 improve thermal performance?

The fused ground lead on the LT1576CS8 reduces thermal resistance from junction to ambient (θ_JA) to 80°C/W when soldered to a large PCB ground plane-approximately 30% lower than standard SO-8 packages. This allows the LT1576CS8 to sustain 125°C junction temperature at higher output currents or ambient temperatures without external heatsinking, critical for sealed portable enclosures.

What happens when the SENSE pin voltage drops below 0.7V on LT1576CS8?

When the SENSE pin voltage on LT1576CS8 falls below 0.7V, the device initiates dual-foldback protection: switching frequency reduces up to 5:1 (e.g., 200kHz → ~40kHz) and peak switch current limit decreases from 1.5A to <0.77A. This limits power dissipation in the IC, external diode, and inductor during short-circuit or severe overload conditions-preventing thermal runaway while maintaining regulation integrity.

Is LT1576CS8 compatible with ceramic output capacitors?

Yes, LT1576CS8 supports ceramic output capacitors, but requires careful attention to ESR and capacitance value. The datasheet specifies 10µF–50µF tantalum (C3) for stability; ceramic equivalents must provide ≥10mΩ effective series resistance (ESR) to dampen control loop peaking. Use X7R or X5R dielectrics ≥1210 case size, and add a 1–2Ω damping resistor in series if instability occurs-verified via load-step transient testing.