STMicroelectronics ST232BD

Overview

ST232BD from STMicroelectronics is a 5 V-powered dual-channel RS-232 transceiver IC with 2 drivers and 2 receivers, compliant with EIA/TIA-232 and V.28 standards. It delivers ±7.8 V transmitter output swing, supports 220 kbps data rate, draws 5 mA supply current at no load, and operates across –40 °C to 85 °C - ideal for battery-powered RS-232 interfaces in portable computers and low-power modems.

For engineers reviewing the ST232BD datasheet, ST232BD pinout, ST232BD application, or ST232BD equivalent, key selection criteria include its single-supply operation, controlled slew rate, ±30 V receiver input tolerance, and compatibility with MAX232/MAX202 footprint and function in embedded serial interface design.

Technical Context

The ST232BD integrates on-chip charge-pump voltage converters to generate ±VCC-derived RS-232 voltage levels from a single 5 V supply, requiring only four 0.1 µF external capacitors. Its dual transmitter/receiver architecture supports full-duplex asynchronous serial communication with TTL/CMOS logic-level interfacing.

It features controlled output slew rate (7–30 V/µs) to reduce EMI, TTL-compatible input thresholds (0.8 V low / 2.0 V high), and robust ±30 V receiver input voltage range with 3–7 kΩ input resistance - enabling reliable operation in electrically noisy industrial and portable environments.

Key Specifications

Pinout & Package

ST232BD is housed in a 16-pin SOIC (SO-16) package with 1.27 mm pitch, RoHS-compliant and ECOPACK® certified. Dimensions: 9.8–10.0 mm × 5.8–6.2 mm × 1.75 mm height.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel RS-232 transceiver applications.

Compared with MAX232ACPE+, ST232BD offers wider temperature range and lower supply current; versus SP3222EBCY-L, it provides higher RS-232 voltage margin and simpler capacitor requirements - making it optimal for industrial 5 V-only designs demanding robustness and ease of use.

Availability

ST232BD is available at Aetrix Electronics and suitable for portable computing, low-power modem design, and battery-powered diagnostic equipment requiring stable component supply and guaranteed long-term sourcing.

Supply support for ST232BD 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 ST232B series belongs to ST's legacy RS-232 interface product line, engineered specifically for cost-sensitive, space-constrained embedded systems needing robust single-supply serial communication without external voltage rails.

FAQ

What is the minimum and maximum supply voltage for reliable operation of ST232BD?

The ST232BD operates reliably from 4.5 V to 5.5 V. Below 4.5 V, transmitter output swing degrades below RS-232 specification (±5 V min), and above 5.5 V risks exceeding absolute maximum ratings. Operation at 5.0 V ±5% ensures full compliance with data rate, slew rate, and output voltage specifications across –40 °C to +85 °C.

Can ST232BD replace MAX232 in an existing design without changes?

Yes - ST232BD is pin-compatible and functionally equivalent to MAX232, including identical SO-16 pinout, same capacitor configuration (0.1 µF), and matching logic thresholds and output drive strength. No PCB or firmware changes are needed, though verify that the –40 °C to +85 °C rating meets system thermal requirements.

Why does ST232BD require four external capacitors, and what happens if their value deviates from 0.1 µF?

The four 0.1 µF capacitors form two charge-pump stages (voltage doubler and inverter). Using values significantly smaller (e.g., 0.01 µF) causes insufficient charge transfer, leading to reduced output voltage swing and data errors at high rates. Larger values (e.g., 1 µF) are acceptable but increase start-up time and board area - ST confirms 0.1 µF as optimal for 220 kbps operation.

Does ST232BD support automatic power-down or shutdown mode?

No - ST232BD has no enable/shutdown pin and remains active whenever VCC is applied. Quiescent current is fixed at 5 mA (typ.) with no load. For ultra-low-power applications requiring sleep mode, consider alternatives like SP3222E or MAX3222, which integrate auto-power-down triggered by TX input inactivity.