Analog Devices Inc. LTC1504CS8-3.3#PBF

Overview

LTC1504CS8-3.3#PBF from Analog Devices (formerly Linear Technology) is a fixed-output 3.3V, 500mA synchronous step-down DC/DC regulator in an SO-8 package. It integrates dual on-chip 1.5Ω MOSFETs, operates from 4V–10V input, delivers up to 92% peak efficiency, and features internal current limiting via IMAX pin - designed for compact, low-part-count power supplies in portable digital systems.

For engineers reviewing the LTC1504CS8-3.3#PBF datasheet, LTC1504CS8-3.3#PBF pinout, LTC1504CS8-3.3#PBF application, or LTC1504CS8-3.3#PBF equivalent, key selection considerations include its fixed 3.3V output with ±3% regulation window, SENSE-pin direct feedback architecture, 200kHz nominal switching frequency (synchronizable to 500kHz), thermal-limited 500mA continuous output, and SO-8 thermal design constraints.

Technical Context

The LTC1504CS8-3.3#PBF implements a synchronous buck topology with integrated P-channel high-side and N-channel low-side MOSFETs. Its feedback loop uses direct SENSE-pin monitoring referenced to a trimmed 3.30V threshold (±3% over temperature), bypassing external resistor dividers. Transient response is enhanced by dedicated MIN/MAX comparators that force full or zero duty cycle when output deviates beyond ±3% of nominal.

Current limiting is implemented via an ILIM amplifier comparing SW-node voltage during Q1 conduction against IMAX-set reference voltage. Soft-start and current-limit functions share the SS pin, where external capacitor value governs both startup slew rate and overload recovery timing. The internal 200kHz sawtooth oscillator supports synchronization up to 500kHz via external clock injection at the COMP pin.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO-8 (S8), exposed pad not present; θJA = 90°C/W, TJMAX = 115°C. Requires minimum 1-inch² copper pour on GND layer under package for thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS62231DRYR and MP2108DQ-LF-Z, the LTC1504CS8-3.3#PBF uniquely supports 10V input and delivers proven 500mA in standard SO-8 without thermal pad, while its MIN/MAX comparators provide faster transient recovery than either alternative - critical for active termination and burst-mode digital loads.

Availability

LTC1504CS8-3.3#PBF is available at Aetrix Electronics and suitable for portable digital systems, active termination circuits, auxiliary voltage supplies, and minimum-part-count switcher designs requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.

Supply support for LTC1504CS8-3.3#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) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving industrial, automotive, communications, and medical markets with robust, precision components.

The LTC1504CS8-3.3#PBF belongs to Linear's legacy µPower synchronous regulator family, engineered for space-constrained, battery-sensitive applications where efficiency, simplicity, and transient robustness outweigh ultra-high-frequency or ultra-low-I_Q requirements.

FAQ

What is the maximum input voltage rating for the LTC1504CS8-3.3#PBF?

The LTC1504CS8-3.3#PBF has an absolute maximum supply voltage (VCC to GND) of 10V, with guaranteed operation specified from 4V to 10V. Operation below 4V is not characterized; factory consultation is required for 2.7V support, and the device is not rated for sustained use at voltages exceeding 10V.

How does the SENSE pin function differ between the LTC1504CS8-3.3#PBF and adjustable versions?

The LTC1504CS8-3.3#PBF uses Pin 5 as SENSE, directly connected to an internal 3.30V reference - it must be tied to the output node for regulation. In contrast, the adjustable LTC1504CS8 uses Pin 5 as FB, requiring an external resistor divider to set output voltage. Mixing these configurations causes regulation failure.

Can the LTC1504CS8-3.3#PBF be synchronized to an external clock?

Yes, the LTC1504CS8-3.3#PBF supports external synchronization up to 500kHz via the COMP pin. An external square-wave clock injected into COMP overrides the internal 200kHz oscillator, enabling EMI reduction and multi-rail phase alignment - confirmed in the Applications Information section and Figure 4b.

What thermal design guidance applies to the LTC1504CS8-3.3#PBF in SO-8 package?

The LTC1504CS8-3.3#PBF has θJA = 90°C/W in standard SO-8. To sustain 500mA at 5V→3.3V, ≥1-inch² copper area connected to Pin 4 (GND) is mandatory. Layout must minimize trace length from GND pin to bulk capacitance and avoid thermal isolation - insufficient copper causes junction temperature to exceed TJMAX = 115°C within seconds under full load.

Does the LTC1504CS8-3.3#PBF require an external Schottky diode for normal operation?

No, the LTC1504CS8-3.3#PBF does not require an external Schottky diode. Its synchronous N-channel rectifier eliminates body-diode conduction losses. A Schottky (e.g., MBRS0530L) may improve efficiency by 1–2% near 500mA but adds cost, board area, and EMI risk - recommended only for marginal thermal designs or extreme reliability validation.