TRS3221EIRGTR - 3-5.5V RS-232 Transceiver, 250kbps, ±15kV ESD | Texas Instruments
MPN: TRS3221EIRGTR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.45 | $2.45 |
| 10 | $2.18 | $21.80 |
| 100 | $1.92 | $192.00 |
| 500 | $1.65 | $825.00 |
| 1,000 | $1.38 | $1,380.00 |
| 3,000 | $1.05 | $3,150.00 |
TRS3221EIRGTR Overview
An RS-232 transceiver is a charge-pump-based interface IC that translates between TTL/CMOS logic levels (0-3.3 V or 0-5 V) and the ±5 V to ±15 V swing required by the legacy TIA/EIA-232-F serial communication standard. RS-232 transceivers belong to the broader interface IC family, which sits hierarchically between discrete level-shifters and protocol controllers (UARTs) in wired communication systems. RS-232 remains widely deployed in industrial equipment, point-of-sale terminals, medical instruments, and embedded debug ports where simplicity, point-to-point connectivity, and proven robustness outweigh the bandwidth advantages of USB or Ethernet.
Key features include ±15 kV Human-Body Model (HBM) ESD protection on RS-232 pins, ±8 kV IEC 61000-4-2 contact discharge, ±15 kV IEC 61000-4-2 air-gap discharge, and an automatic powerdown feature that disables drivers when no valid RS-232 cable is detected. The on-chip dual charge pump requires only four external 0.1 µF capacitors, enabling true 5 V operation from a single 3.3 V supply without a separate ±12 V rail. The 250 kbps data rate is adequate for all standard RS-232 baud rates up to and beyond 115200 with margin to spare.
The architecture combines a regulated switched-capacitor voltage doubler/inverter with a proprietary low-dropout RS-232 driver stage and a precision hysteresis receiver. ESD protection is implemented at the cable-side pins using TI's integrated silicon-controlled-rectifier (SCR) clamps. The 16-pin VQFN package's exposed pad provides a low thermal resistance path, which is useful when the part operates near the upper end of its 1 mA quiescent current budget in warm enclosures.
Typical applications include industrial PLC programming ports, point-of-sale (POS) terminals, medical device serial consoles, battery-powered handhelds, and embedded debug UARTs that need robust ESD performance in the field. The TRS3221EIRGTR's small 3x3 mm footprint suits space-constrained designs such as USB-to-serial dongles, IoT gateways, and barcode scanners.
When designing with this part, place the four charge-pump capacitors as close as possible to the C1+ / C1- / C2+ / C2- pins and keep the RS-232 trace lengths short to maximize ESD margin. Note that the TRSF3221E is the higher-speed (1 Mbit/s) pin-compatible alternative if 250 kbps is insufficient. This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for TRS3221EIRGTR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
TRS3221EIRGTR
✅ Drop-In✓ In Stock
$1.05 / Unit
View Datasheet →SN75C3221EIRGTR
✅ Drop-In📋 Reference alternative (not in catalog)
TRSF3221EIRGTR
✅ Drop-In📋 Reference alternative (not in catalog)
MAX3221EIRGTR
✅ Drop-In📋 Reference alternative (not in catalog)
TRS3221EIRGTR Specifications
| Function | RS-232 line driver/receiver (transceiver) |
| Number of Drivers | 1 |
| Number of Receivers | 1 |
| Data Rate | 250 kbps |
| Supply Voltage (VCC) | 3.0 V to 5.5 V |
| Logic Supply Voltage | Same as VCC (no separate VL pin) |
| RS-232 Driver Output Swing | ±5.4 V minimum into 5 kΩ load |
| Receiver Input Voltage Range | ±25 V |
| Receiver Hysteresis | 0.5 V typical |
| ESD Protection (HBM, RS-232 pins) | ±15 kV |
| ESD Protection (IEC 61000-4-2 contact) | ±8 kV |
| ESD Protection (IEC 61000-4-2 air-gap) | ±15 kV |
| Quiescent Current (powered, no load) | 1 mA typical |
| Auto Powerdown Feature | Yes (drivers disable when no valid RS-232 signal detected) |
| External Capacitors Required | 4 × 0.1 µF ceramic |
| Operating Temperature | -40 °C to +85 °C |
| Package | VQFN-16 (RGT) 3 × 3 mm with exposed pad |
| Mounting Type | Surface Mount |
| MSL Level | 2 (1 year floor life at ≤30 °C / 60 % RH) |
| RoHS Status | Compliant |
| Lead Finish | NiPdAu lead-free |
| Standards Compliance | TIA/EIA-232-F, ITU v.28 |
TRS3221EIRGTR Pin Configuration
| Pin 1 | DOUT — Driver input (TTL/CMOS, from UART TX) |
| Pin 2 | DIN — Receiver output (TTL/CMOS, to UART RX) |
| Pin 3 | GND — Ground |
| Pin 4 | C1+ — Charge-pump flying capacitor positive terminal |
| Pin 5 | V+ — Charge-pump +5.4 V generated rail |
| Pin 6 | C1- — Charge-pump flying capacitor negative terminal |
| Pin 7 | C2+ — Charge-pump flying capacitor positive terminal |
| Pin 8 | C2- — Charge-pump flying capacitor negative terminal |
| Pin 9 | V- — Charge-pump -5.4 V generated rail |
| Pin 10 | GND — Ground |
| Pin 11 | VCC — Supply voltage, 3.0 V to 5.5 V |
| Pin 12 | RIN — Receiver input (RS-232, ±25 V tolerant) |
| Pin 13 | ROUT — Receiver output (TTL/CMOS, to UART RX) |
| Pin 14 | NC — Not connected (per datasheet) |
| Pin 15 | NC — Not connected (per datasheet) |
| Pin 16 | EPAD — Exposed thermal pad - tie to GND for thermal dissipation |
Typical Applications
TRS3221EIRGTR is suitable for 6 applications: Industrial PLC Programming Port, Point-of-Sale (POS) Terminal Serial Console, Medical Device Service/Diagnostic Port, USB-to-Serial Dongle, Battery-Powered Handheld Scanner, Embedded Firmware Debug UART.
Industrial PLC Programming Port
The TRS3221EIRGTR is well suited to industrial PLC programming ports because its ±15 kV HBM and ±15 kV IEC 61000-4-2 air-gap ESD ratings protect the cable-side pins from charged-cable discharge when technicians hot-plug a programming terminal. The 250 kbps data rate covers all common PLC vendor baud rates (9600, 19200, 38400, 57600, 115200) with margin, while the 3.0-5.5 V VCC range lets the same part interface with both legacy 5 V PLC logic and newer 3.3 V microcontrollers. Place four 0.1 µF X7R capacitors near the charge-pump pins to ensure stable ±5.4 V rail generation even on long factory cables. The exposed thermal pad helps dissipate heat in sealed IP65 enclosures without airflow.
Recommended
Point-of-Sale (POS) Terminal Serial Console
POS terminals require a robust debug and service console port that survives accidental cable mis-wiring and static discharge from cashiers. The TRS3221EIRGTR's ±25 V receiver input range tolerates the ±12-15 V transients seen on poorly shielded RJ45-to-DB9 cables in retail environments, and the auto-powerdown feature disables drivers when no cable is attached, cutting idle current for energy-star compliance. The 16-pin VQFN (RGT) 3×3 mm package fits inside the tight enclosures of modern POS card readers, and the 1 mA quiescent current keeps total standby power below 5 mW at 5 V. The exposed pad provides a low thermal resistance path when the part sits adjacent to a warm printer stepper driver.
Recommended
Medical Device Service/Diagnostic Port
Medical equipment such as infusion pumps and patient monitors require IEC 60601-1-compliant RS-232 service ports for biomed technicians to download event logs and run calibration routines. The TRS3221EIRGTR meets the ±15 kV IEC 61000-4-2 air-gap ESD requirement that simplifies the overall IEC 60601-1-2 EMC certification, reducing retest cycles when the connector is touched by a charged operator. The 3.0-5.5 V supply integrates cleanly with the 3.3 V rails used by modern ARM Cortex-M host MCUs such as the STM32L4 family. Reliable 250 kbps data rate ensures that 1 MB log dumps complete in under one minute, minimizing downtime in clinical settings.
Recommended
USB-to-Serial Dongle
Compact USB-to-serial bridge dongles benefit from the TRS3221EIRGTR's 3×3 mm VQFN footprint, which fits inside the DB-9 hood alongside a USB-C connector and a CP2102N bridge IC. The 250 kbps data rate supports legacy equipment at any standard baud rate, while the ±15 kV ESD on the DB-9 pins protects the dongle from charged cable discharge when users hot-plug into industrial equipment. The integrated charge pump eliminates the need for a bulky ±12 V switching regulator, allowing the entire dongle to draw less than 10 mA from the USB 5 V rail. Operating temperature range of -40 to +85 °C accommodates outdoor field-engineering laptops.
Recommended
Battery-Powered Handheld Scanner
Battery-powered barcode scanners and rugged handhelds use the TRS3221EIRGTR as a charging-crate communication port, where its 1 mA quiescent current preserves battery life between docking events. The auto-powerdown feature automatically disables the RS-232 drivers when no cable is connected, dropping standby consumption below 1 µA when the device is in its cradle. The 3.0-5.5 V supply lets the part share a single Li-ion battery rail directly without a boost converter. The VQFN-16 3×3 mm package occupies minimal PCB area in compact handheld enclosures, freeing space for the lithium battery and barcode imager.
Recommended
Embedded Firmware Debug UART
Embedded development boards expose a TTL-level UART header for firmware debugging, but many legacy firmware tools and lab bench equipment still expect a full RS-232 port with ±5 V swing. The TRS3221EIRGTR bridges this gap on a 16-pin VQFN footprint with the ±5.4 V swing required to drive RS-232 inputs on test equipment such as spectrum analyzers and protocol analyzers. The wide 3.0-5.5 V VCC range means the same board can use a 3.3 V STM32 or a 5 V Arduino without modification. ±15 kV ESD protects the lab environment from charged fixture discharge during repeated connection cycles.
Recommended
Recommended Products Summary
Engineering reference data for TRS3221EIRGTR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SN75C3221EIRGTR | TRSF3221EIRGTR | MAX3221EIRGTR |
|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices (Maxim) |
| Package | VQFN-16 (RGT) 3×3 mm | VQFN-16 (RGT) - same | VQFN-16 (RGT) - same | VQFN-16 (RGT) - same |
| Supply Voltage | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V |
| Data Rate | 250 kbps | 250 kbps | 1000 kbps (1 Mbit/s) | 250 kbps |
| ESD (HBM, RS-232 pins) | ±15 kV | ±15 kV | ±15 kV | ±15 kV |
| ESD (IEC 61000-4-2 air-gap) | ±15 kV | ±15 kV | ±15 kV | ±15 kV |
| Number of Drivers / Receivers | 1 / 1 | 1 / 1 | 1 / 1 | 1 / 1 |
| External Capacitors Required | 4 × 0.1 µF | 4 × 0.1 µF | 4 × 0.1 µF | 4 × 0.1 µF |
| Auto-Powerdown | Yes | Yes | Yes | Yes |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
Key Differentiators
- Single-channel VQFN-16 RGT footprint with on-chip auto-powerdown (vs MAX3232 (multi-channel SOIC-16 wide))
- 250 kbps data rate with same pinout as 1 Mbit/s variant (vs TRSF3221EIRGTR)
- Cross-vendor second source with identical electrical behavior (vs MAX3221EIRGTR (Analog Devices / Maxim))
Design Notes
Place the four 0.1 µF charge-pump capacitors (C1+, C1-, C2+, C2-) as close as physically possible to their respective pins on the TRS3221EIRGTR. Keep trace lengths below 5 mm and use 0.1 µF X7R or X5R ceramic capacitors rated for at least 16 V. Wide ground and VCC traces under the exposed thermal pad improve charge-pump stability and reduce radiated emissions from the switched-capacitor converter.
The RS-232 receiver input pins (RIN) tolerate up to ±25 V of input voltage, but the receiver output (ROUT/DIN) is TTL/CMOS logic referenced to VCC. If the host MCU runs at 1.8 V and the TRS3221EIRGTR runs at 3.3 V or 5 V, add a series resistor (10-100 kΩ) on ROUT/DIN to limit current during logic-level mismatch; the receiver outputs are push-pull CMOS and can source/sink several mA.
Do not substitute the four 0.1 µF charge-pump capacitors with electrolytic or tantalum types; the charge-pump switching frequency requires low-ESR ceramic capacitors to maintain regulation. Ensure the exposed thermal pad (EPAD, pin 16) is soldered to a properly grounded copper pour of at least 25 mm² for thermal dissipation and electrical reference; an unsoldered EPAD can cause the internal charge pump to misbehave and increase EMI.
Keep the RS-232 output traces (TDOUT) routed away from sensitive analog or high-speed digital signals. The TRS3221EIRGTR's charge pump operates at approximately 250 kHz, and its harmonics can couple into nearby analog circuitry. A ground guard trace between the RS-232 cable-side pins and the TTL/CMOS side pins, stitched with ground vias every 5 mm, suppresses common-mode coupling.
Estimated: at 5 V VCC with no RS-232 cable connected and auto-powerdown active, the part draws approximately 1 µA. With a 5 kΩ RS-232 load on TDOUT, the part draws approximately 20-30 mA peak from VCC due to the charge-pump efficiency loss and driver output current. Decouple VCC with a 0.1 µF ceramic capacitor in parallel with a 1 µF bulk ceramic placed within 10 mm of the VCC pin.
Compliance Information
RoHS and REACH compliant per TI product page. Not AEC-Q100 qualified — choose TRS3221EI-Q1 suffix variant for automotive applications. Halogen-free status not explicitly stated in the provided data — verify with TI's full material declaration if required for your end-market.
