STMicroelectronics ALTAIR04-900TR

Overview

ALTAIR04-900 from STMicroelectronics is a high-voltage off-line all-primary-sensing switching regulator IC integrating a 900 V avalanche-rugged power MOSFET and a current-mode PWM controller in a single SO16N package. It enables optocoupler-free constant voltage (CV) and adjustable constant current (CC) regulation for quasi-resonant flyback converters, with 166 kHz top-limited switching frequency, 0.75 V current-sense threshold, and 2.5 V internal error amplifier reference - deployed in energy metering SMPS and industrial auxiliary supplies.

For engineers reviewing the ALTAIR04-900 datasheet, ALTAIR04-900 pinout, ALTAIR04-900 application, or ALTAIR04-900 equivalent, this device delivers primary-side CV/CC regulation without secondary feedback components, supports mains-independent overload protection, features integrated HV start-up (5.5 mA typical charge current), and implements valley-skipping and burst-mode operation to meet stringent standby power requirements.

Technical Context

The ALTAIR04-900 implements a current-mode quasi-resonant flyback controller with transformer demagnetization sensing via the ZCD/FB pin, enabling valley-switching turn-on synchronized to negative-going edges below 70 mV. Its dual-function ZCD/FB input performs both zero-current detection and output voltage sampling-and-hold for CV regulation using an internal 2.5 V reference and transconductance error amplifier (gm = 2.2 mS typ.).

It integrates a 900 V, 16 Ω (25 °C) avalanche-rated power section with leading-edge blanking (250 ns typ.), hiccup-mode OCP triggered at 1 V sensed across Rsense, and a self-powered HV start-up generator delivering 5.5 mA to Vcc until 13 V is reached. The IREF pin establishes CC regulation via adaptive voltage reference (0.4 V typ.) and automatic peak current adjustment.

Key Specifications

Pinout & Package

ALTAIR04-900 is housed in a thermally enhanced SO16N package with exposed drain pads (pins 13–16) connected to the internal metal frame for efficient heat dissipation. The copper area beneath drain pins must be maximized per layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICE3BR1765J and LNK364PG, the ALTAIR04-900 uniquely combines 900 V avalanche ruggedness, integrated HV start-up, and true primary-side CV/CC regulation - enabling smaller, more reliable, and certification-ready designs for energy metering and industrial auxiliary supplies.

Availability

ALTAIR04-900 is available at Aetrix Electronics and suitable for energy metering SMPS, industrial auxiliary supplies for 3-phase systems, and AC-DC adapters requiring stable component supply, long-lifecycle support, and compliance with IEC 62053 and EN 50160.

Supply support for ALTAIR04-900 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 high-reliability off-line AC-DC conversion, specifically engineered for primary-side regulated flyback topologies in utility metering and industrial power supplies where optocoupler elimination and surge resilience are critical.

FAQ

What is the purpose of the ZCD/FB pin's dual functionality?

The ZCD/FB pin serves two verified roles: first, it detects the negative-going edge of the auxiliary winding voltage to synchronize MOSFET turn-on at the transformer demagnetization valley (quasi-resonant operation); second, it samples and holds the peak voltage at the end of demagnetization to derive output voltage information for constant voltage regulation - eliminating need for optocoupler feedback while maintaining ±1% accuracy.

How does the ALTAIR04-900 achieve mains-independent constant current regulation?

Mains independence is achieved through voltage feed-forward implemented via the ZCD/FB pin: the current sourced by this pin during MOSFET on-time is monitored and used to compensate for line voltage variation in the current-sense path. This results in a fixed average output current regardless of input voltage changes, with RFF = 45 Ω defining the feed-forward gain - confirmed in Section 5.6 of the datasheet.

Can the ALTAIR04-900 operate without an auxiliary winding?

No - an auxiliary winding is mandatory. It provides the ZCD signal for valley detection and CV regulation, supplies the IC during normal operation (via Vcc rectification), and enables accurate current sensing during CC mode. The HV start-up generator only supplements Vcc during startup or fault conditions; sustained operation requires auxiliary winding energy transfer.

What thermal design considerations apply to the SO16N package?

The SO16N package uses pins 13–16 as exposed drain terminals bonded to the internal metal frame; these pins must be soldered to a large copper pour acting as a heatsink. Thermal resistance junction-to-pin is 10 °C/W, so a minimum 400 mm² copper area (2 oz Cu) is recommended to maintain Tj ≤ 125 °C at 0.9 W dissipation - validated in Table 3 and Figure 2 layout notes.