STMicroelectronics ITA18B3

Overview

ITA18B3 from STMicroelectronics is a bidirectional Transil™ diode array for high-energy transient suppression on differential data lines, featuring 18 V breakdown voltage (VBR), 21 V clamping voltage at 10 A (VCL), 40 A peak pulse current (8/20 µs), 300 W peak pulse power, and 500 pF junction capacitance per I/O pair - deployed in RS-485 and RS-422 interface protection.

For engineers reviewing the ITA18B3 datasheet, ITA18B3 pinout, ITA18B3 application, or ITA18B3 equivalent, key selection criteria include its 4-point separated input/output architecture for ESD-induced di/dt spike elimination, ±9.0 V max differential voltage rating between inputs, and SO-20 package compatibility with industrial serial communication layouts.

Technical Context

The ITA18B3 integrates 610 unidirectional Transil diodes with common cathode to deliver up to nine independent bidirectional protection channels. Its 4-point structure physically separates input and output terminals to eliminate parasitic inductance-induced overshoot during fast transients like ESD (IEC 61000-4-2 Level 4).

It operates with 18 V minimum breakdown voltage (VBR), clamps to 21 V at 10 A IPP, and maintains ≤5 µA leakage current at 15 V VRM. Junction capacitance is 500 pF per I/O pair at 0 V bias (1 MHz), enabling use on moderate-speed differential buses without signal integrity degradation.

Key Specifications

Pinout & Package

ITA18B3 is housed in a standard SO-20 (Small Outline, 20-pin) package with 1.27 mm pitch, compliant with JEDEC MS-013, UL94 V0 epoxy, and ECOPACK® lead-free interconnect.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional transient protection applications.

Compared with SMA6J18A and SP1012-010, ITA18B3 uniquely delivers nine coordinated bidirectional channels in one SO-20 footprint with 4-point I/O isolation - essential for maintaining signal fidelity and surge margin in multi-line industrial serial interfaces.

Availability

ITA18B3 is available at Aetrix Electronics and suitable for RS-485 infrastructure, industrial HMI serial ports, and factory automation control panels requiring stable component supply and long-term obsolescence management.

Supply support for ITA18B3 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The ITAxxB3 series belongs to ST's Transil™ monolithic TVS array product line, engineered specifically for high-fidelity, multi-line data interface protection where ESD immunity, surge robustness, and layout-driven noise rejection are co-design requirements.

FAQ

What is the maximum allowable differential voltage between two input pins for ITA18B3?

The maximum differential voltage between any two input pins is ±9.0 V at 25 °C, as specified in Table 3 of the datasheet. This limit ensures safe operation without forward-biasing internal diode junctions during common-mode transients or miswiring conditions, preserving device longevity and clamping accuracy.

Can ITA18B3 be used to protect USB 2.0 data lines?

No - ITA18B3's 500 pF junction capacitance per I/O pair exceeds USB 2.0 specification limits (<10 pF typical), causing excessive signal rise-time degradation and eye diagram closure. It is intended for lower-speed differential buses like RS-422/RS-485 (≤20 Mbps), not high-speed protocols requiring strict impedance and capacitance control.

Does ITA18B3 require external series resistance for ESD compliance?

No external series resistance is required to meet IEC 61000-4-2 Level 4 (15 kV air / 8 kV contact). The device's low clamping factor (VCL/VBR = 1.17) and 4-point architecture provide direct, low-inductance protection. Adding series resistance would degrade response time and increase clamping voltage, counteracting its design intent.

How does the 4-point structure improve ESD protection compared to conventional TVS arrays?

The 4-point structure separates input and output terminals to break the current loop formed by PCB traces and ground planes. This eliminates L·di/dt voltage spikes induced by ESD current flowing through shared parasitic inductance - a key failure mode in conventional single-terminal TVS devices - thereby delivering cleaner clamping waveforms and higher system-level immunity.