STMicroelectronics ALTAIR05T-800TR

Overview

ALTAIR05T-800 from STMicroelectronics is an off-line all-primary sensing quasi-resonant flyback switching regulator IC integrating an 800 V avalanche-rugged power MOSFET and a low-voltage PWM controller in a single SO16N package. It delivers constant voltage (CV) and constant current (CC) regulation without optocoupler, achieves ≤±5% load transient CV/CC accuracy, supports 85–265 VAC input, and enables <30 mW standby power in AC-DC mobile phone chargers.

For engineers reviewing the ALTAIR05T-800 datasheet, ALTAIR05T-800 pinout, ALTAIR05T-800 application, or ALTAIR05T-800 equivalent, this page provides verified pin functions, primary-sensing CV/CC regulation behavior, SO16N thermal derating data, cable drop compensation implementation, and validated alternatives for compact, no-opto SMPS designs.

Technical Context

The ALTAIR05T-800 implements quasi-resonant (QR) operation via ZCD/FB pin demagnetization detection with programmable arming (100–120 mV) and triggering (50–70 mV) thresholds, enabling valley-switching across line/load conditions up to 166 kHz max. Its internal transconductance error amplifier (gm = 1.3–3.2 mS, GBW = 500 kHz) drives COMP pin for loop stability with 2.5 V reference (±2% over temperature).

Primary-side CC regulation uses IREF pin with adaptive capacitor-based current reference (VIREFx = 1.5–1.7 V), while mains-independent CC is achieved via ZCD/FB feedforward (RFF = 45 Ω equivalent). Cable drop compensation (CDC) adjusts CV setpoint via external resistor between CDC and ZCD/FB pins, sinking up to 200 µA at 2.5 V reference.

Key Specifications

Pinout & Package

ALTAIR05T-800 is housed in a SO16N package with exposed drain pads (pins 13–16) for enhanced thermal dissipation (Rth j-pin = 10 °C/W). The copper pour under drain pins must be designed per ST's layout recommendations to maintain Tj ≤ 150 °C at 0.9 W Ptot.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar off-line quasi-resonant flyback controller applications.

Compared with ICE5QSAG and LNK364PG, ALTAIR05T-800 uniquely combines 800 V ruggedness, no-opto CV/CC, and analog CDC - enabling tighter output regulation across variable cable lengths and universal AC input without secondary sensing.

Availability

ALTAIR05T-800 is available at Aetrix Electronics and suitable for AC-DC mobile chargers, USB-C power adapters, IoT smart plug power supplies, and Bluetooth headset charging cases requiring stable component supply, full-production qualification, and long-term lifecycle support.

Supply support for ALTAIR05T-800 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 industrial, automotive, and consumer markets.

The ALTAIR series targets highly integrated, no-opto AC-DC conversion for compact chargers and adapters, emphasizing primary-side regulation accuracy, low standby power, and robust avalanche-rated power stages.

FAQ

What is the purpose of the IREF pin and how is it used in constant current regulation?

The IREF pin hosts an external capacitor that develops a dynamically adjusted voltage reference (1.5–1.7 V) used to set the MOSFET peak drain current during constant current (CC) mode. As output load changes, the internal circuit modulates this voltage to maintain constant average output current without secondary sensing. A typical 100 nF ceramic capacitor is placed between IREF and GND to stabilize the reference and ensure fast CC response to load steps.

Can ALTAIR05T-800 operate without an auxiliary winding, and what are the trade-offs?

Yes - the internal HV start-up generator allows initial power-up and sustained operation directly from the rectified mains, especially critical during CC regulation when auxiliary winding voltage may fall below UVLO. However, for ultra-low no-load consumption (<15 mW), powering via the auxiliary winding is mandatory, as the HV generator draws ~5.5 mA continuously during burst mode, increasing idle loss.

How does the ZCD/FB pin perform both demagnetization detection and output voltage sensing?

During transformer demagnetization, a negative-going edge on ZCD/FB triggers MOSFET turn-on. At the exact end of demagnetization, the pin voltage is sampled and held - this value is proportional to the reflected output voltage and fed to the error amplifier's inverting input. Simultaneously, ZCD/FB current magnitude (up to ±2 mA) encodes input voltage for feedforward CC regulation, enabling mains-independent current accuracy.

What thermal design considerations apply to the SO16N package given its 0.9 W power dissipation?

With Rth j-amb = 110 °C/W, 0.9 W dissipation causes ~99 °C junction rise above ambient - exceeding the 150 °C max if ambient exceeds 51 °C. Therefore, copper pour under pins 13–16 (drain) is essential; ST recommends ≥250 mm² of 2-oz copper connected to internal ground plane. Thermal vias under drain pads and minimized trace length between DRAIN and bulk capacitor further reduce Rth j-amb to ≤70 °C/W in optimized layouts.