STMicroelectronics TSM1012AIST

Overview

TSM1012AIST from STMicroelectronics is a dual-loop SMPS controller IC for secondary-side voltage and current regulation in flyback adapters and battery chargers. It integrates a 1.25 V ±0.5% precision reference, two transconductance op-amps with ORed sink outputs, operates from 4.5–28 V supply, consumes only 100–180 µA, and supports -40 to +105 °C operation.

For engineers reviewing the TSM1012AIST datasheet, TSM1012AIST pinout, TSM1012AIST application, or TSM1012AIST equivalent, this device is selected for precise CV/CC feedback in isolated AC-DC power supplies where low quiescent current, high PSRR (65–100 dB), and minimal external components are critical.

Technical Context

The TSM1012AIST implements independent voltage and current control loops using two transconductance operational amplifiers whose outputs are wired-ORed to a single open-collector sink output (OUT). The internal 1.25 V reference feeds both loops: one amplifier compares CV+ and CV− to regulate output voltage; the other compares CC+ and CC− against a Vref-derived threshold to limit output current.

Its SO-8 package exposes all key nodes-VRef, both op-amp inputs (CV±, CC±), GND, VCC, and OUT-enabling full external compensation via accessible negative inputs and the output node. The device features built-in 28 V VCC clamp and achieves 70–85 dB common-mode rejection over temperature.

Key Specifications

Pinout & Package

Package: SO-8 (Small Outline, 150 mil width), RoHS-compliant ECOPACK®.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-loop SMPS feedback applications.

Compared with TL431+LM358 and UCC3803-1, the TSM1012AIST delivers integrated dual-loop control in one SO-8 package with guaranteed 0.5% reference precision, <180 µA ICC, and direct optocoupler drive-reducing design time, component count, and thermal stress in space-constrained adapters.

Availability

TSM1012AIST is available at Aetrix Electronics and suitable for smartphone fast charging adapters, laptop AC adapters, and industrial battery maintenance chargers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for TSM1012AIST 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 microcontrollers, power ICs, sensors, and analog devices for automotive, industrial, and consumer markets.

The TSM1012AIST belongs to ST's dedicated SMPS secondary-side controller product line, engineered specifically for high-accuracy, low-power CV/CC regulation in isolated flyback converters used in energy-efficient AC-DC adapters and battery chargers.

FAQ

What is the maximum sink current capability of the TSM1012AIST OUT pin?

The OUT pin provides a current-sink capability of 5–10 mA depending on temperature and input differential. At 25 °C, short-circuit current is typically 6 mA when sinking into (VCC − 0.6 V); minimum guaranteed is 5 mA across -40 to +105 °C. This directly drives standard optocoupler LEDs without external transistors.

Can the TSM1012AIST operate with a 3.3 V supply?

No. The absolute minimum VCC is 4.5 V per Table 4, and typical operation starts reliably above 5 V. Below 4.5 V, internal reference and op-amp biasing become unstable, causing loss of regulation. For 3.3 V systems, a local LDO or charge pump is required to generate ≥4.5 V for the TSM1012AIST.

How does the TSM1012AIST handle start-up under short-circuit conditions?

During start-up or output short-circuit, VCC may fall below 4.5 V due to shared auxiliary supply. The TSM1012AIST then loses regulation capability; current limiting relies entirely on the primary-side PWM controller. To ensure safe start-up, either select a primary controller with precise current foldback or add a dedicated low-dropout regulator for the TSM1012AIST's VCC.

Is external compensation mandatory for stable operation?

Yes. Both op-amp loops require external compensation: the CV loop uses a series RC network between CV− and OUT; the CC loop uses a similar network between CC− and OUT. ST recommends 2.2 nF + 22 kΩ per loop (Figure 6). Omitting compensation causes oscillation or sluggish response, especially with long optocoupler leads or high-capacitance feedback paths.