Diodes Incorporated PT8A3285PEX

Overview

PT8A3285PEX from Pericom Semiconductor is a mixed-signal CMOS heating controller IC designed for 120V/240V AC-powered thermal appliances. It implements proportional temperature control using an external NTC sensor, features dual-voltage auto-detection, NTC open-circuit protection, and delivers 5–15mA TRIAC trigger pulses. Used in hair straighteners and curling irons, it integrates a 5-bit ADC, internal Zener (5.0V), and programmable heating timer (~1.2h at 50Hz).

For engineers reviewing the PT8A3285PEX datasheet, PT8A3285PEX pinout, PT8A3285PEX application, or PT8A3285PEX equivalent, key selection considerations include its TRIAC-compatible GATE output, dual-voltage line frequency sensing (50/60Hz), NTC1/NTC2 open-detection interface, 8-pin DIP-8 package, and LED1/LED2 dual-indicator drive capability.

Technical Context

The PT8A3285PEX operates as a closed-loop thermal controller that samples NTC voltage via NTC1, detects open-circuit faults via NTC2, and synchronizes to AC line frequency through CLK. Its internal 5-bit ADC digitizes NTC voltage for proportional control calculation, while the state machine manages heating-on/off transitions and timer expiration (216,000 clock cycles).

It generates precise 160–240µs TRIAC trigger pulses on GATE with 5mA sink capability, supports dual LED indication (LED1/LED2) with flash modes (1/32 and 1/8 CLK frequency), and includes internal POR (1.5–2.5V) and Zener regulation (4.5–5.5V at 500µA–10mA).

Key Specifications

Pinout & Package

PT8A3285PEX is supplied in a lead-free 8-pin DIP (JEDEC MS-001D/BA compliant) with 2.54mm pitch, 9.0–9.4mm body width, and 6.2–6.6mm body length. Thermal design accommodates continuous operation in compact enclosures.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PT8A3284PEX and PT8A3286PEX, PT8A3285PEX uniquely provides constant-on LED1 with functional LED2-enabling two independent status indicators without external logic, critical for dual-mode appliance UIs.

Availability

PT8A3285PEX is available at Aetrix Electronics and suitable for hair straighteners, curling irons, and electric blanket controllers requiring stable component supply, RoHS-compliant packaging, and long-term industrial availability.

Supply support for PT8A3285PEX 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 (now part of Diodes Incorporated) specialized in high-performance interface, timing, and power management ICs for consumer and industrial applications.

The PT8A328x series was developed specifically for cost-sensitive, safety-critical thermal appliances-integrating analog sensing, digital control, and power interface in a single 8-pin package.

FAQ

What is the function of the NTC2 pin on PT8A3285PEX?

NTC2 is an open-drain output that pulls low during NTC open-circuit detection. It works in conjunction with NTC1 to verify NTC continuity: when NTC1 shows no valid voltage and NTC2 asserts low, the IC enters safe shutdown. This dual-pin method avoids false triggers from noise or transient disconnection.

Can PT8A3285PEX drive a TRIAC directly without an optocoupler?

No-PT8A3285PEX's GATE pin provides 5mA sink current at 0.5V, sufficient to drive the LED side of a standard opto-TRIAC (e.g., MOC3021), but not a bare TRIAC gate. Direct TRIAC drive would violate isolation requirements and exceed safe operating area limits for consumer appliance safety certifications.

How does PT8A3285PEX distinguish between 120V and 240V line operation?

It uses the CLK input frequency: 60Hz indicates 120V operation and 50Hz indicates 240V. The internal control algorithm adjusts proportional output duty cycle accordingly-higher voltage lines receive shorter effective firing angles to maintain consistent thermal output and prevent overheating.

Is the internal Zener diode intended for external use?

Yes-the 5.0V Zener (4.5–5.5V range at 500µA–10mA) can supply bias current for external LEDs or optocouplers. However, total current drawn must stay within 500mW package power limit; typical use is 1–2mA per LED with series resistor, verified under worst-case VDD and ambient temperature.