STMicroelectronics ITA18B1

Overview

ITA18B1 from STMicroelectronics is a bidirectional Transil™ diode array for differential data line protection, featuring 18 V standoff voltage (VRM), 28 V clamping voltage at 40 A (VCL @ IPP), 350 pF junction capacitance, and ±9.0 V maximum differential voltage between I/O pins. It delivers 300 W peak pulse power (8/20 µs) and meets IEC 61000-4-2 Level 4 ESD immunity (15 kV air, 8 kV contact) in SO-8 package for RS-422/RS-485 interface protection.

For engineers reviewing the ITA18B1 datasheet, ITA18B1 pinout, ITA18B1 application, or ITA18B1 equivalent, key selection criteria include clamping performance under 40 A surge, low-leakage operation (<10 µA at 18 V), differential voltage tolerance (±9.0 V), and SO-8 footprint compatibility with industrial serial transceivers.

Technical Context

The ITA18B1 integrates six unidirectional Transil diodes with a common cathode, configured to provide up to five independent bidirectional protection channels between I/O pins and GND. Its clamping action responds within nanoseconds to transient overvoltages, limiting voltage excursions to ≤28 V during 40 A 8/20 µs pulses while maintaining <10 µA leakage at rated standoff.

Designed for differential signaling lines, it enforces a maximum ±9.0 V differential voltage between any two I/O pins per Table 3, ensuring safe operation with RS-422/RS-485 drivers operating at ±7 V nominal common-mode range. Junction capacitance of 350 pF at VRM supports signal integrity up to ~10 Mbps on balanced lines.

Key Specifications

Pinout & Package

ITA18B1 is housed in a standard SO-8 surface-mount package compliant with JEDEC MS-012, UL94 V0 epoxy, and ECOPACK® lead-free interconnect standards. Dimensions: 4.90 mm × 6.00 mm × 1.75 mm (L × W × H), 1.27 mm lead pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional data-line protection applications.

Compared with SMA6J18A and SP1003-010, ITA18B1 uniquely combines quad bidirectional protection, ±9.0 V differential tolerance, and 300 W surge capacity in one SO-8 device-making it optimal for robust RS-485/RS-422 node hardening where space and common-mode resilience are critical.

Availability

ITA18B1 is available at Aetrix Electronics and suitable for RS-485 industrial bus protection, RS-422 differential link protection, and RS-232 port surge suppression requiring stable component supply and long-term lifecycle support.

Supply support for ITA18B1 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 ITAxxB1 series belongs to ST's Transil™ transient voltage suppression portfolio, engineered specifically for high-reliability differential data line protection in harsh electromagnetic environments.

FAQ

What is the maximum allowable differential voltage between I/O pins on ITA18B1?

The ITA18B1 specifies a maximum differential voltage of ±9.0 V between any two I/O pins at 25 °C, as defined in Table 3 of the datasheet. Exceeding this value risks internal diode breakdown due to the monolithic common-cathode architecture. This limit is critical for proper operation on RS-485 buses where common-mode swings can reach ±7 V.

Does ITA18B1 require external current-limiting resistors in RS-485 applications?

No external current-limiting resistors are required for transient suppression, as the ITA18B1 clamps directly between I/O and GND. However, series resistors (e.g., 10–33 Ω) are still recommended between the transceiver and bus to damp ringing and limit steady-state fault current-consistent with TIA-485-A guidelines and independent of the Transil's operation.

How does ITA18B1's 350 pF capacitance affect RS-485 signal integrity?

With 350 pF measured between each I/O pin and GND at 1 MHz, the ITA18B1 adds minimal loading to standard RS-485 stubs. At 10 Mbps, this capacitance contributes <1 ns of additional rise-time degradation when combined with typical 50 Ω termination, remaining within TIA-485-A timing budgets for distances up to 1200 m.

Is ITA18B1 compatible with lead-free reflow soldering processes?

Yes, ITA18B1 is supplied in an ECOPACK®-compliant SO-8 package with lead-free second-level interconnects, qualified for standard Pb-free reflow profiles (JEDEC J-STD-020). The maximum lead temperature is rated at 260 °C for 10 seconds at 5 mm from the case, matching IPC/JEDEC specifications for SnAgCu soldering.