STMicroelectronics ST3222BTR

Overview

ST3222BTR from STMicroelectronics is a 3 V to 3.6 V, low-power RS-232 transceiver IC with two drivers and two receivers, 300 µA supply current, 250 kbps guaranteed data rate, and ±5.4 V true RS-232 output swing. It integrates an internal charge pump requiring only four 0.1 µF capacitors and supports active receiver monitoring during 1 mA shutdown mode. Used in battery-powered portable computers and peripherals.

For engineers reviewing the ST3222BTR datasheet, ST3222BTR pinout, ST3222BTR application, or ST3222BTR equivalent, key selection criteria include guaranteed 250 kbps operation at 3 V, TSSOP20 package compatibility, shutdown current ≤10 µA, receiver input range of ±25 V, and EIA/TIA-232 compliance down to 3 V supply.

Technical Context

The ST3222BTR implements dual-channel RS-232 driver/receiver functionality using a proprietary low-dropout transmitter stage and charge-pump voltage converter generating ±5.5 V rails from 3–3.6 V VCC. Its logic-compatible inputs accept TTL/CMOS levels, while receivers tolerate ±25 V input and deliver CMOS/TTL outputs with V_OH ≥ V_CC−0.6 V and V_OL ≤ 0.4 V.

Timing is characterized with 240–400 kbps data rate (RL = 3 kΩ, CL = 1000 pF), 0.2 µs receiver propagation delay, and 6 V/µs minimum slew rate. The device supports independent receiver enable (EN) and global shutdown (SHDN) control, enabling selective power management without disabling receiver monitoring capability.

Key Specifications

Pinout & Package

ST3222BTR is housed in a 20-pin TSSOP (Thin Shrink Small Outline Package) with 0.65 mm pitch, JEDEC MO-153 compliant, and ECOPACK®-compliant for RoHS and halogen-free requirements.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3222CSE+ and SP3222ECA-L, ST3222BTR offers identical functional performance with tighter 300 µA active current spec and integrated charge pump architecture requiring only four capacitors-reducing layout complexity and cost in space-constrained portable designs.

Availability

ST3222BTR is available at Aetrix Electronics and suitable for industrial serial gateways, medical handheld diagnostics, point-of-sale peripheral interfaces, ruggedized field data loggers, and battery-powered computing equipment requiring stable component supply across extended temperature ranges.

Supply support for ST3222BTR 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 microcontrollers, analog ICs, power management devices, and sensors for industrial, automotive, and consumer markets.

The ST3222BTR belongs to ST's RS-232 interface product line, engineered specifically for low-voltage, low-power serial communication in portable and battery-operated systems where EIA/TIA-232 compliance must be maintained without external high-voltage supplies.

FAQ

What is the minimum supply voltage required for ST3222BTR to meet EIA/TIA-232 specifications?

The ST3222BTR guarantees full EIA/TIA-232 compliance-including ±5 V output swing and ±25 V receiver tolerance-down to 3.0 V supply. Operation below 3.0 V is not characterized; output swing degrades below specification, and receiver thresholds shift outside guaranteed margins per Table 7.

Can ST3222BTR operate with only one transmitter or receiver enabled?

Yes. The EN pin controls both receivers independently, allowing R1OUT and R2OUT to enter high-impedance state while transmitters remain active. Transmitters have no individual enable; they are controlled globally via SHDN. This enables asymmetric use cases such as modem status monitoring with transmit-only operation.

What capacitor values are required for ST3222BTR's charge pump, and why are they critical?

Four 0.1 µF ceramic capacitors (C1+, C1−, C2+, C2−) are mandatory per the datasheet. These stabilize the internal charge pump generating ±5.5 V rails. Using larger values increases startup time and may cause overshoot; smaller values reduce voltage regulation margin and risk output swing collapse under load, directly violating RS-232 voltage compliance.

Does ST3222BTR support automatic power-down when no data is transmitted?

No. ST3222BTR lacks auto-power-down circuitry. Power state is controlled solely by the SHDN pin (active-low) and EN pin (active-low). To minimize power during idle periods, the host system must assert SHDN or disable receivers via EN-both require explicit GPIO control from the connected microcontroller or UART controller.