Texas Instruments TRS3221CDBG4

Overview

TRS3221CDBG4 from Texas Instruments is a single-driver, single-receiver RS-232 transceiver IC with ±15-kV HBM ESD protection on RS-232 pins, 3-V to 5.5-V supply operation, automatic power-down capability (1-μA standby current), and INVALID status output for RS-232 signal presence detection - used in portable serial interfaces requiring robust electrostatic immunity and low-power sleep modes.

For engineers reviewing the TRS3221CDBG4 datasheet, TRS3221CDBG4 pinout, TRS3221CDBG4 application, or TRS3221CDBG4 equivalent, key selection considerations include its 250-kbps data rate, dual control inputs (FORCEON/FORCEOFF) for autonomous driver enable/disable, ±15-kV ESD rating on RIN/DOUT, 0.1-μF capacitor requirement, and TSSOP-16 package compatibility with space-constrained embedded designs.

Technical Context

The TRS3221CDBG4 integrates a charge-pump voltage converter generating ±5.5-V rails from a single 3.3-V or 5-V supply, enabling true RS-232 voltage levels without external dual supplies. Its receiver features hysteresis (0.5-V typical) and input thresholds of ±2.7 V for valid signal detection, while the INVALID output asserts low when RIN remains within –0.3 V to +0.3 V for >30 μs - indicating loss of valid RS-232 link.

Power management is implemented via FORCEON and FORCEOFF logic inputs: when FORCEON = low and FORCEOFF = high, automatic power-down activates if no valid RS-232 signal is detected at RIN, disabling DOUT and reducing ICC to 1 μA. The EN pin independently controls ROUT high-impedance state, decoupling receiver output from system logic during idle.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00 mm × 4.40 mm body size), 0.65-mm pitch, surface-mount, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN65C3221IPWR, TRS3221CDBG4 trades speed for lower system cost and smaller layout area; compared with MAX3232ESE+, it reduces capacitor count by 75% and shrinks package size by 38%, making it ideal for ultra-compact portable electronics where board space and BOM count are critical.

Availability

TRS3221CDBG4 is available at Aetrix Electronics and suitable for industrial serial gateways, medical handheld diagnostic tools, smart energy meters, ruggedized field data loggers, and battery-powered point-of-sale terminals requiring stable component supply across multi-year production cycles.

Supply support for TRS3221CDBG4 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

Texas Instruments is a global semiconductor leader delivering analog and embedded processing solutions, with over 50 years of innovation in interface, power management, and signal chain technologies.

The TRS3221CDBG4 belongs to TI's RS-232 transceiver product line, engineered specifically for low-power, ESD-hardened serial communication in portable, medical, and industrial edge devices operating from single 3.3-V or 5-V rails.

FAQ

What is the maximum data rate supported by the TRS3221CDBG4?

The TRS3221CDBG4 supports a maximum data signaling rate of 250 kbps under recommended operating conditions with 1000-pF load capacitance and 3-kΩ load resistance. This rate is validated per TIA/EIA-232-F compliance testing and maintains full RS-232 voltage swing (±5.4 V) and timing margins. Exceeding this rate may result in degraded signal integrity or non-compliant output levels.

Does the TRS3221CDBG4 require external charge-pump capacitors, and what values are specified?

Yes, the TRS3221CDBG4 requires four external ceramic capacitors for its internal charge pump: C1+, C1−, C2+, and C2−. For 3.3-V operation, 0.1-μF capacitors are specified; for 5-V operation, 0.047-μF (C1) and 0.33-μF (C2–C4) are recommended. These values ensure stable ±5.5-V rail generation and meet switching characteristic specifications across temperature and voltage ranges.

How does the INVALID output function on the TRS3221CDBG4, and what is its electrical behavior?

The INVALID output on the TRS3221CDBG4 is an open-drain, active-low status pin that goes low when the RIN input remains within –0.3 V to +0.3 V for more than 30 μs - indicating loss of valid RS-232 signal. It asserts high when RIN exceeds ±2.7 V. INVALID operates independently of FORCEON/FORCEOFF states and remains functional as long as VCC is powered, enabling reliable link monitoring without software polling.

Can the TRS3221CDBG4 operate from a 3.3-V supply while accepting 5-V logic inputs on DIN, FORCEON, and FORCEOFF?

Yes, the TRS3221CDBG4 accepts 5-V logic inputs on DIN, FORCEON, and FORCEOFF even when powered from a 3.3-V VCC supply. Its input structure tolerates VI up to 5.5 V, eliminating the need for external level shifters when interfacing with mixed-voltage systems - a key advantage over many legacy RS-232 transceivers that require strict 3.3-V-only logic inputs.

What is the purpose of the EN pin on the TRS3221CDBG4, and how does it interact with the receiver?

The EN (Enable) pin on the TRS3221CDBG4 controls the output state of the receiver (ROUT). When EN is high, ROUT is placed in high-impedance (tri-state), disconnecting the receiver output from the host UART RX line. When EN is low, ROUT actively drives logic-high or logic-low based on RIN voltage. This allows hardware-controlled receiver isolation during system sleep or multiplexed bus configurations without firmware involvement.