STMicroelectronics SEA05TR

Overview

SEA05TR from STMicroelectronics is a dual-loop SMPS controller IC implementing constant voltage (CV) and constant current (CC) regulation via integrated transconductance op-amps, 2.5 V bandgap reference, and low-side current sensing. It operates from 3.5–36 V_VCC, draws only 200 µA quiescent current, features ±0.5% voltage loop accuracy and 50 mV current sense threshold, and targets compact AC-DC adapters and battery chargers.

For engineers reviewing the SEA05TR datasheet, SEA05TR pinout, SEA05TR application, or SEA05TR equivalent, key selection criteria include its SOT23-6L package size, open-drain OR-ed output stage for optocoupler interfacing, dual-loop compensation flexibility, and robustness against negative voltage transients on Ictrl during output short-circuit events.

Technical Context

The SEA05TR integrates two independent transconductance op-amps: one forms the voltage control loop with Vctrl as inverting input and internal 2.5 V reference, the other forms the current control loop with Isense (inverting) and Ictrl (non-inverting) inputs and fixed 50 mV threshold. Both outputs are OR-ed into a single open-drain OUT pin capable of sinking up to 20 mA.

Its architecture enables square-shaped V/I limiting behavior - voltage regulation dominates until current limit is reached, then current regulation clamps output. Compensation networks connect directly to OUT and Vctrl/Ictrl pins, allowing full loop stability tuning without external op-amp buffers.

Key Specifications

Pinout & Package

SEA05TR is housed in a JEDEC-standard SOT23-6L micro package (3.05 mm × 1.75 mm × 1.45 mm), optimized for space-constrained AC-DC adapters and USB-C chargers. Its pin layout supports direct PCB routing to current-sense resistors and optocouplers with minimal parasitic coupling.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar constant voltage and constant current controller applications.

Compared with UC3842BD1R2G and TL431ACDBVR, SEA05TR delivers true monolithic dual-loop control in SOT23-6L, eliminating 6–10 external components while achieving ±0.5% CV and ±8% CC accuracy - critical for safety-certified chargers and energy-efficient adapters.

Availability

SEA05TR is available at Aetrix Electronics and suitable for USB-C PD adapters, lithium-ion battery chargers, and industrial AC-DC power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SEA05TR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The SEA05TR belongs to ST's dedicated SMPS controller product line, engineered specifically for compact, isolated flyback and forward converters requiring integrated CV/CC regulation without secondary-side complexity.

FAQ

What is the maximum recommended sense resistor power rating for SEA05TR in a 2 A charger application?

For I_max = 2 A and V_csth = 50 mV, Rsense = 25 mΩ and power dissipation P_lim = V_csth × I_max = 100 mW. ST recommends using a 0.125 W (1/8 W) or higher rated resistor with adequate thermal relief on PCB to ensure reliability under continuous full-load operation.

Can SEA05TR operate with V_CC derived solely from the auxiliary winding without bulk capacitor?

Yes - SEA05TR's 3.5 V minimum V_CC and 200 µA quiescent current allow startup and operation directly from an auxiliary winding, even with minimal or no bulk capacitance, provided the winding delivers ≥3.5 V under all load and line conditions and includes a series diode and RC snubber.

How does the OR-ed output stage affect loop interaction during simultaneous CV and CC conditions?

The OR-ed output ensures the more demanding loop (lower output voltage) dominates - if both loops request correction, the stronger sink current wins. This prevents conflicting signals and guarantees monotonic V/I limiting behavior, producing the square characteristic shown in Figure 5 without external logic.

Is external compensation mandatory for stable operation?

No - SEA05TR is internally compensated for basic applications, but external R-C networks on Vctrl and OUT pins are required to optimize phase margin across full line/load range, especially in high-frequency or high-power designs. ST provides design equations and stability guidelines in Section 7 of the datasheet.