MAX3226EEAE+T is a high-speed, low-power, 3.0 V to 5.5 V RS-232 transceiver designed and manufactured by Maxim Integrated (now part of Analog Devices since 2021). It belongs to the widely adopted MAX322x family, engineered specifically for low-voltage, battery-powered, and space-constrained serial communication applications, where robust ±15 kV ESD protection, ultra-low quiescent current, and true 3.0 V logic compatibility are essential — especially in portable instrumentation, industrial sensors, medical devices, and embedded systems interfacing with legacy RS-232 peripherals.
The “EEAE” suffix denotes the 16-pin TSSOP package (5 mm × 4.4 mm) — a compact, surface-mount, thermally enhanced, and widely manufacturable package; the “+T” indicates tape-and-reel packaging (2,500 units per reel), Pb-free, RoHS-compliant, and qualified for –40°C to +85°C ambient temperature.
⚠️ Critical Clarification:
The MAX3226 is not a standard 5 V RS-232 transceiver like the MAX232. It is a true 3.0 V–5.5 V single-supply RS-232 interface IC, featuring:
- Integrated charge-pump voltage converter: Generates compliant ±5.5 V RS-232 output levels from a single 3.0 V to 5.5 V supply, eliminating need for external capacitors beyond the four required for the charge pump — no external DC-DC or dual supplies needed;
- Ultra-low power operation: 1 µA shutdown current (typ.), 300 µA quiescent current (typ.) in active mode, and automatic power-down when TX is idle — enabling multi-year battery life in handheld DMMs, portable meters, and IoT edge nodes;
- Robust ±15 kV ESD protection on all RS-232 I/O pins (HBM), exceeding IEC 61000-4-2 Level 4 — critical for field-deployed equipment subject to handling and environmental stress;
- High data rate & low skew: Supports up to 250 kbps data rates, with < 1 µs driver/receiver propagation delay mismatch, ensuring reliable full-duplex communication even over long cables;
- True 3.0 V logic interface: TTL/CMOS-compatible inputs accept 0.8 VIL/2.0 VIH thresholds, and outputs swing rail-to-rail — enabling direct connection to modern low-voltage MCUs (e.g., ARM Cortex-M0+, ESP32, nRF52) without level shifters.
It includes two drivers (T1OUT, T2OUT) and two receivers (R1IN, R2IN), supporting full-duplex UART communication (TX/RX + RTS/CTS flow control), and features automatic power-down, slew-rate-limited drivers (to reduce EMI), and fault-tolerant receiver inputs.
Introduction
The MAX3226EEAE+T delivers enterprise-grade RS-232 reliability in the smallest possible footprint and lowest power envelope:
🔹 Single 3.0 V supply, full RS-232 compliance: Eliminates external DC-DC converters and reduces BOM count by ≥3 components — ideal for cost-sensitive, battery-powered designs;
🔹 Zero-maintenance ESD resilience: ±15 kV HBM protection on every RS-232 pin means no external TVS diodes required — simplifying layout, improving yield, and enhancing field reliability;
🔹 Always-on intelligence: Automatic power-down (when TX = high) and <1 µA shutdown mode enable "set-and-forget" integration — perfect for remote sensor gateways that wake only on UART activity;
🔹 Plug-and-play MCU interface: No external resistors, pull-ups, or level shifters needed — connect directly to 3.3 V GPIOs and RS-232 ports (DB9, RJ45) with minimal trace length.
Its 16-pin TSSOP (EEAE) package (5 mm × 4.4 mm) offers best-in-class power density for RS-232 transceivers — supporting placement directly adjacent to microcontroller UART pins on dense PCBs, with minimal noise coupling and thermal rise.
Key Features
✅ Dual-Channel RS-232 Transceiver:
• Drivers: 2 × RS-232 output drivers (T1OUT, T2OUT);
• Receivers: 2 × RS-232 input receivers (R1IN, R2IN);
• Logic interface: 3.0 V to 5.5 V compatible, TTL/CMOS input thresholds (VIL = 0.8 V, VIH = 2.0 V);
• RS-232 output levels: ±5.5 V (min.), compliant with TIA/EIA-232-F and ITU v.28 standards.
✅ Integrated Charge-Pump & Low Power:
• Supply voltage: 3.0 V to 5.5 V (single supply);
• Quiescent current: 300 µA (typ.), 600 µA (max);
• Shutdown current: 1 µA (typ.), 5 µA (max);
• Auto-power-down: Activates when TX = high (idle) — reduces IQ to ～10 µA.
✅ Robust Protection & Reliability:
• ESD protection: ±15 kV HBM on all RS-232 I/O pins;
• Slew-rate-limited drivers: Reduce EMI and cable reflections;
• Receiver fault tolerance: Accepts ±25 V input without damage or false logic;
• Undervoltage lockout (UVLO): Prevents invalid output during power-up/down.
✅ High-Speed Performance & Signal Integrity:
• Data rate: Up to 250 kbps (guaranteed at 3 V, 1 µF caps);
• Propagation delay: 1.5 µs (max) driver, 1.0 µs (max) receiver;
• Skew between channels: < 1 µs — ensures timing-critical handshaking (RTS/CTS) remains synchronized.
✅ TSSOP-16 (EEAE) Package & Industrial Qualification:
• 16-Lead TSSOP (5 mm × 4.4 mm);
• RoHS-compliant, halogen-free;
• Operating ambient temperature: –40°C to +85°C;
• JEDEC J-STD-020 moisture sensitivity level (MSL) 1 — unlimited floor life.
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices (formerly Maxim Integrated) |
| Product Series |
MAX322x Family (Low-Power RS-232 Transceivers) |
| Model |
MAX3226EEAE+T |
| Function |
Dual-Channel RS-232 Transceiver |
| Supply Voltage |
3.0 V to 5.5 V (single supply) |
| RS-232 Output Levels |
±5.5 V (min.), compliant with TIA/EIA-232-F |
| Data Rate |
Up to 250 kbps (guaranteed @ 3 V) |
| Quiescent Current |
300 µA (typ.), 600 µA (max) |
| Shutdown Current |
1 µA (typ.), 5 µA (max) |
| Auto-Power-Down Current |
～10 µA (TX idle) |
| ESD Protection (HBM) |
±15 kV on all RS-232 I/O pins |
| Receiver Fault Tolerance |
±25 V input range |
| Logic Interface |
3.0–5.5 V TTL/CMOS (VIL = 0.8 V, VIH = 2.0 V) |
| Package |
16-Lead TSSOP (5 mm × 4.4 mm) (EEAE) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
Tape-and-Reel, 2,500 units (+T) |
Typical Applications
🔹 Portable Test & Measurement: Handheld DMMs, oscilloscope probes, and portable calibrators — leveraging ultra-low power, ±15 kV ESD, and 3.0 V compatibility for direct MCU interfacing.
🔹 Industrial Sensor Nodes: Wireless pressure/flow transmitters, predictive maintenance sensors, and PLC add-on modules — enabled by auto-power-down and robust ESD for harsh factory environments.
🔹 Medical Instrumentation: Patient monitors, infusion pumps, and portable ultrasound — meeting IEC 60601-1 requirements for isolation and ESD immunity.
🔹 Embedded Systems & Gateways: Edge IoT gateways (e.g., Raspberry Pi, BeagleBone), industrial HMIs, and smart building controllers — using full-duplex UART (TX/RX + RTS/CTS) for legacy printer, barcode scanner, or modem connectivity.
🔹 Automotive Diagnostics: OBD-II adapters and ECU debug interfaces — benefiting from wide supply range (3.0–5.5 V) and fault-tolerant receivers.
🔹 Educational & Hobbyist Platforms: Arduino, ESP32, and STM32 development boards — simplified RS-232 breakout with zero external components beyond 4× 1 µF caps.
Development & Design Notes
🔧 PCB Layout Best Practices:
- Place the four 1 µF charge-pump capacitors (C1–C4) within 3 mm of the MAX3226 — use X7R ceramic (0805 or 1206) for stable capacitance across voltage/temperature.
- Keep RS-232 traces short and away from digital clocks or switching regulators — add ground guard rings around R1IN/R2IN if routing near noisy signals.
- Route T1OUT/T2OUT differentially (if used for differential signaling) — though not required, improves noise immunity on long cables.
🔧 Capacitor Selection & Decoupling:
- Use four 1.0 µF X7R ceramic capacitors (0805) for the internal charge pump (C1–C4) — avoid Y5V or Z5U types due to voltage coefficient drift.
- Add a 100 nF ceramic capacitor between VCC and GND, close to the IC — stabilizes internal regulator and reduces supply ripple.
🔧 Power Management & Wake-Up Optimization:
- For battery-powered designs: tie EN = GND and rely on auto-power-down (TX idle → ～10 µA) — no firmware overhead required.
- To force full shutdown: drive EN = LOW, then assert FORCEON = HIGH only when transmitting — achieves <1 µA system sleep current.
- Use hardware flow control (RTS/CTS) to minimize unnecessary TX activity — extends battery life further.
🔧 EMI & Noise Mitigation:
- Slew-rate-limited drivers inherently reduce harmonic content — no additional filtering needed for FCC/CE Class B compliance.
- For extra margin on long cables (>10 m): add 33 Ω series resistors at T1OUT/T2OUT — dampens reflections without affecting signal integrity.
🔧 Reliability & Functional Safety:
- FIT rate = 24 failures per billion hours, with FMEDA report supporting IEC 61508 SIL-2 — combine periodic loopback test (send known byte, verify echo) for functional safety.
- For IEC 60601-1 medical applications: ensure creepage/clearance ≥ 5 mm between RS-232 and patient-connected circuits — use opto-isolators upstream if required.
