Diodes Incorporated PT8A3281PEX

Overview

PT8A3281PEX from Pericom Semiconductor is a mixed-signal CMOS heating controller IC designed for dual-voltage (120V/240V) AC-powered thermal appliances. It implements proportional temperature control using an external NTC sensor, provides NTC open-circuit protection, delivers 15mA SCR gate trigger pulses (160–240μs width), and integrates internal Zener regulation (4.5–5.5V). It is used in hair curlers and straighteners requiring automatic power adaptation and timed heating cycles.

For engineers reviewing the PT8A3281PEX datasheet, PT8A3281PEX pinout, PT8A3281PEX application, or PT8A3281PEX equivalent, key selection considerations include its 8-pin DIP package, 50/60Hz line-synchronized CLK input, GATE output drive capability, NTC1/NTC2 sensing interface, and 1.2-hour auto-off timer at 50Hz - all critical for safe, compliant thermal appliance design.

Technical Context

The PT8A3281PEX uses a 5-bit ADC to digitize NTC voltage for closed-loop proportional temperature regulation. Its internal state machine transitions between Reset, Heating-On, and Heating-Off modes, with automatic voltage detection (via CLK amplitude) selecting appropriate control curves for 120V or 240V operation.

It features dual LED drivers (LED1/LED2) with configurable flash patterns (1/32 or 1/8 CLK frequency), a dedicated GATE output for SCR triggering, and hardware-level NTC open detection via NTC1/NTC2 pins - enabling fail-safe shutdown without firmware intervention.

Key Specifications

Pinout & Package

PT8A3281PEX is supplied in an 8-pin lead-free DIP package (JEDEC MS-001D/BA), with 0.3-inch body width and 2.54mm pitch. Pin 1 is marked by notch or dot; leads are tin-plated and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar heating controller applications.

Compared with PT8A3285WE, PT8A3281PEX offers SCR compatibility and DIP packaging for through-hole assembly, while PT8A3280PEX differs only in LED1 behavior - making it a drop-in replacement where flash indication is acceptable and no PCB redesign is needed.

Availability

PT8A3281PEX is available at Aetrix Electronics and suitable for hair styling tools, electric blankets, and beauty device thermal modules requiring stable component supply, long-lifecycle support, and RoHS-compliant manufacturing.

Supply support for PT8A3281PEX 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

Pericom Semiconductor was a fabless analog/mixed-signal IC designer specializing in timing, interface, and power management solutions before its acquisition by Diodes Incorporated in 2016.

The PT8A328x series belongs to Pericom's thermal control product line, engineered specifically for cost-sensitive, safety-critical AC-heating applications in consumer personal care devices - emphasizing integration, reliability, and regulatory compliance over programmability.

FAQ

What is the function of the NTC2 pin on PT8A3281PEX?

The NTC2 pin is an open-drain output that goes low when the NTC sensor is detected as open-circuited. It is not a measurement pin but a fault signaling terminal tied to the internal NTC open-detection circuit. This pin can drive an external LED or connect to a microcontroller interrupt to initiate system-level safety shutdown, ensuring compliance with IEC 60335-1 Clause 22.12.

Can PT8A3281PEX operate directly from rectified AC without a linear regulator?

Yes - PT8A3281PEX includes an internal Zener diode (4.5–5.5V) that regulates VDD from an unregulated DC supply derived from rectified AC. When paired with a current-limiting resistor (e.g., 43kΩ/2W as shown in the application circuit), it accepts 12–24V DC input and maintains stable operation without external LDOs or capacitors beyond the recommended 0.1μF bypass.

How does PT8A3281PEX distinguish between 120V and 240V line voltages?

It analyzes the amplitude of the CLK input signal, which is derived from the AC line via a resistive divider. High-amplitude CLK corresponds to 240V operation and selects a steeper proportional control curve; low-amplitude CLK selects the 120V curve. This hardware-based detection occurs at power-up and requires no configuration or calibration - enabling true dual-voltage interoperability.

Is the GATE output compatible with standard SCRs like the MCR106-6?

Yes - the GATE output delivers 15mA peak current with 160–240μs pulse width, exceeding the 10mA/10μs minimum gate trigger requirement of the MCR106-6 and similar sensitive-gate SCRs. The output is rated for 5mA sink current at 0.5V, ensuring reliable turn-on even under elevated junction temperatures up to +85°C.