STMicroelectronics TSM1051CLT

Overview

TSM1051CLT from STMicroelectronics is a constant voltage (CV) and constant current (CC) controller IC for secondary-side feedback in flyback battery chargers and AC/DC adaptors. It integrates dual transconductance op-amps with ORed outputs, a 1.210 V ±0.5% bandgap voltage reference, and a –200 mV current-sense threshold. Designed for space-constrained applications, it operates from 2.5 V to 12 V supply and delivers up to 50 mA sink output current.

For engineers reviewing the TSM1051CLT datasheet, TSM1051CLT pinout, TSM1051CLT application, or TSM1051CLT equivalent, this device supports precise CV/CC regulation in isolated SMPS using optocoupler-based feedback - critical for USB-C PD adapters, Li-ion charger designs, and low-power universal input adaptors requiring tight output tolerance and robust short-circuit behavior.

Technical Context

The TSM1051CLT implements two independent control loops: a voltage loop using an internal 1.210 V reference and a transconductance amplifier (Gmv = 3.5 mA/mV), and a current loop referenced to –200 mV at Vsense with Gmi = 7 mA/mV. Both amplifiers share a common current-sink output stage (OUT pin), enabling automatic ORing between CV and CC modes.

Its SOT23-6 package provides direct access to all control inputs (Vctrl, Ictrl, Vsense), ground, supply (VCC), and output - supporting full external compensation via accessible negative inputs and output nodes. The device requires only three external components for basic operation: a resistor divider for voltage setting, a sense resistor for current limiting, and optional RC networks for loop stability.

Key Specifications

Pinout & Package

Housed in a compact SOT23-6 package (2.8 × 1.5 mm, 0.95 mm pitch), the TSM1051CLT uses surface-mount construction compatible with high-density PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC28704DR, the TSM1051CLT offers faster time-to-market and simpler certification due to proven optocoupler-based architecture; compared with TL431-based solutions, it delivers tighter regulation, lower component count, and guaranteed CV/CC coordination without external logic.

Availability

TSM1051CLT is available at Aetrix Electronics and suitable for USB-C adaptors, smartphone battery chargers, and universal-input AC/DC power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for TSM1051CLT 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, specializing in power management, analog, and microcontroller technologies for industrial, automotive, and consumer markets.

The TSM1051 belongs to ST's dedicated SMPS secondary-side controller product line, engineered specifically for high-accuracy, low-component-count CV/CC regulation in isolated flyback converters used in energy-efficient charging and adaptor applications.

FAQ

What is the minimum VCC voltage required for TSM1051CLT to enter regulation?

The TSM1051CLT begins functional operation at 2.5 V VCC and achieves full CV/CC regulation capability above 3.0 V. Below 2.5 V, internal biasing fails and the output stage disables. For reliable start-up in flyback designs, the auxiliary winding must deliver ≥3.3 V within 5 ms of initial conduction to ensure stable feedback loop engagement before primary-side overcurrent protection activates.

How does the ORed output stage prevent conflict between voltage and current loops?

The two transconductance amplifiers share a common collector output node (OUT pin), creating a wired-OR configuration. When either loop demands increased sink current - e.g., Vctrl error rises or Ictrl error falls - the resulting currents sum at the OUT pin. This ensures the more restrictive condition (lower voltage or higher current) dominates optocoupler drive, guaranteeing immediate transition to current limit without software or external logic.

Can TSM1051CLT be used with synchronous rectification controllers?

Yes - the TSM1051CLT is fully compatible with secondary-side synchronous rectifier drivers such as STSR3 or MP6908. Its OUT pin sinks current only and does not source, so it interfaces directly with the SR controller's feedback input without level-shifting. The CV/CC regulation remains independent of rectifier timing, preserving efficiency gains while maintaining output accuracy.

What is the recommended Rsense power rating for a 2 A current limit?

For a 2 A current limit, Rsense = 200 mV / 2 A = 100 mΩ. Power dissipation is P = Vsense × Ilim = 0.2 V × 2 A = 400 mW. A 0.5 W (½ W) metal-film or thick-film resistor with 1% tolerance and low TCR is recommended to maintain accuracy across temperature and avoid thermal drift-induced current error.