Analog Devices Inc. LTC3531EDD-3.3#TRPBF

Overview

LTC3531EDD-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a synchronous 4-switch buck-boost DC/DC converter in a 3mm × 3mm DFN package, delivering up to 200mA at fixed 3.3V output from input voltages ranging 1.8V–5.5V. It features Burst Mode® operation (16μA quiescent current), integrated 0.5Ω NMOS and 0.8Ω PMOS switches, and seamless mode transition for single-cell Li-Ion or multi-cell alkaline power rails.

For engineers reviewing the LTC3531EDD-3.3#TRPBF datasheet, LTC3531EDD-3.3#TRPBF pinout, LTC3531EDD-3.3#TRPBF application, or LTC3531EDD-3.3#TRPBF equivalent, key selection criteria include input voltage range compatibility with battery discharge profiles, output disconnect capability during shutdown, thermal performance with exposed pad soldering, and minimal external component count (only three passive components required for fixed-output operation).

Technical Context

The LTC3531EDD-3.3#TRPBF implements a true 4-switch topology with independent control of NMOS (A/B) and PMOS (C/D) pairs, enabling continuous conduction across buck, boost, and 4-switch modes without discontinuity. Its VBEST and mode-detect circuitry dynamically selects optimal switching sequence based on real-time VIN–VOUT differential.

It integrates anticross-conduction logic to prevent shoot-through, uses a 1.225V internal reference for 3.3V regulation (±1.2% over temperature), and employs IPEAK/IVALLEY sensing with tOFF timing (~3μs in 4SW mode) to optimize efficiency and load transient response across 0.1–200mA loads.

Key Specifications

Pinout & Package

The LTC3531EDD-3.3#TRPBF is housed in an 8-lead 3mm × 3mm plastic DFN package with exposed thermal pad (Pin 9, connected to GND). The package requires soldering of the exposed pad to PCB ground plane for thermal compliance (θJA = 43°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck-boost converter applications.

Compared with LTC3440EDD-3.3#TRPBF and TPS63020DSJR, the LTC3531EDD-3.3#TRPBF uniquely combines ultra-low quiescent current, guaranteed output disconnect, and seamless mode transition - making it optimal for battery-powered systems requiring long shelf life and strict power domain isolation.

Availability

LTC3531EDD-3.3#TRPBF is available at Aetrix Electronics and suitable for handheld medical sensors, USB-powered IoT edge nodes, industrial handheld scanners, and wearable health trackers requiring stable component supply with consistent parametric performance across production batches.

Supply support for LTC3531EDD-3.3#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 its precision analog and power management product lines with full technical documentation and long-term support.

The LTC3531 series was designed specifically for ultra-low-power, single-inductor buck-boost conversion in portable battery-operated equipment where input voltage may fall above, below, or equal to the required output voltage.

FAQ

What is the minimum input voltage required for the LTC3531EDD-3.3#TRPBF to start up and regulate 3.3V?

The LTC3531EDD-3.3#TRPBF has a minimum startup voltage of 1.65V (typical) and guarantees operation down to 1.8V across temperature. Below 1.65V, the UVLO circuit prevents switching; once VIN exceeds this threshold, the part enters start-up mode using the D-body diode until VOUT reaches ~1.6V, then transitions to full 4-switch regulation.

Does the LTC3531EDD-3.3#TRPBF provide true output disconnect during shutdown?

Yes, the LTC3531EDD-3.3#TRPBF actively opens both PMOS rectifiers (switches A and D) when SHDN is pulled low, isolating VOUT from VIN and allowing the output to discharge to 0V. This eliminates backfeed risk and meets stringent power-domain isolation requirements in USB and battery-backed systems.

Can the LTC3531EDD-3.3#TRPBF operate efficiently at very light loads, such as 100μA?

Yes, the LTC3531EDD-3.3#TRPBF achieves >80% efficiency at 100μA load via Burst Mode® operation, drawing only 16μA quiescent current. Its adaptive pulse-skipping algorithm minimizes switching losses while maintaining tight output regulation - ideal for always-on sensor nodes.

What is the recommended inductor value and rating for use with the LTC3531EDD-3.3#TRPBF?

An inductor value of 10μH to 22μH with ≥500mA saturation current and <400mΩ DCR is recommended for the LTC3531EDD-3.3#TRPBF. Ferrite-core types (e.g., Murata LQH43CN100K03) are preferred for low core loss; shielded or toroidal variants reduce radiated EMI in noise-sensitive applications.

Is the exposed thermal pad on the LTC3531EDD-3.3#TRPBF package electrically connected, and how should it be handled in PCB layout?

Yes, the exposed pad (Pin 9) of the LTC3531EDD-3.3#TRPBF is internally connected to GND and must be soldered to a dedicated PCB ground plane using multiple thermal vias. Failure to do so degrades thermal performance (θJA increases from 43°C/W to >80°C/W) and risks thermal shutdown under sustained 200mA load.