Texas Instruments MAX3221CDBR

Overview

MAX3221CDBR from Texas Instruments is a 3-V to 5.5-V single-driver, single-receiver RS-232 transceiver with ±15-kV HBM ESD protection on bus pins, 250-kbps data rate capability, automatic power-down (1 µA standby current), and integrated charge-pump circuitry requiring only four 0.1-µF capacitors. It interfaces UART logic to legacy RS-232 ports in battery-powered industrial handhelds and embedded computing systems.

For engineers reviewing the MAX3221CDBR datasheet, MAX3221CDBR pinout, MAX3221CDBR application, or MAX3221CDBR equivalent, key selection considerations include its SSOP-16 package, dual control inputs (FORCEON/FORCEOFF) for autonomous power management, INVALID status flag for receiver signal validity detection, and compatibility with 3.3-V logic while accepting 5-V inputs.

Technical Context

The MAX3221CDBR implements a dual-stage charge-pump architecture generating ±5.5-V rails from a single 3.3-V or 5-V supply, enabling full RS-232 voltage compliance without external high-voltage sources. Its driver delivers ±5.4-V output swing into 3-kΩ loads, while the receiver features 3–7-kΩ input resistance and hysteresis (0.5 V) for noise immunity.

Functional modes are governed by FORCEON (active-high enable) and FORCEOFF (active-high disable) pins: when FORCEON = low and FORCEOFF = high, automatic power-down activates if no valid RS-232 signal (>±2.7 V or <±0.3 V for <30 µs) is detected at RIN, disabling DOUT and reducing ICC to 1 µA; INVALID asserts low after 30 µs of indeterminate input.

Key Specifications

Pinout & Package

MAX3221CDBR is housed in a 16-pin SSOP (DB) package measuring 6.20 mm × 5.30 mm, optimized for compact industrial and portable PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3232CDBR and SN65C3221IPWR, the MAX3221CDBR delivers optimal cost, power, and size efficiency for single-channel RS-232 links where 250-kbps throughput suffices and automatic power-down is critical for battery longevity.

Availability

MAX3221CDBR is available at Aetrix Electronics and suitable for industrial handheld terminals, embedded industrial PCs, and portable medical devices requiring stable component supply, long-term lifecycle support, and traceable sourcing for regulated markets.

Supply support for MAX3221CDBR 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, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The MAX3221CDBR belongs to TI's RS-232 interface product line, engineered specifically for low-power, ESD-hardened serial communication in space- and energy-constrained embedded systems.

FAQ

What is the maximum data rate supported by the MAX3221CDBR?

The MAX3221CDBR supports a maximum data signaling rate of 250 kbps under recommended operating conditions with CL = 1000 pF and RL = 3 kΩ. This is validated across the full 0°C to 70°C temperature range and 3.0–5.5-V supply, making it suitable for standard UART communication in industrial and portable applications. Higher rates risk signal integrity degradation due to slew-rate limiting.

How does the automatic power-down feature function in the MAX3221CDBR?

The MAX3221CDBR enters automatic power-down when FORCEON is low and FORCEOFF is high. In this mode, if no valid RS-232 signal (|RIN| > ±2.7 V or within ±0.3 V for <30 µs) is detected, the driver output DOUT is disabled and supply current drops to 1 µA typical. The INVALID pin goes low after 30 µs of indeterminate input, signaling the host controller that the link is inactive.

Which external capacitors are required for MAX3221CDBR operation?

The MAX3221CDBR requires four 0.1-µF ceramic capacitors connected to C1+, C1−, C2+, and C2− pins for charge-pump operation at 3.3-V supply. At 5-V supply, TI recommends C1 = 0.047 µF and C2–C4 = 0.33 µF. A 0.1-µF bypass capacitor on VCC is also mandatory. All capacitors must be nonpolarized ceramics placed close to the IC per layout guidelines.

What is the purpose of the INVALID output pin on the MAX3221CDBR?

The INVALID pin on the MAX3221CDBR is an open-drain status indicator that asserts low when the RIN input remains within ±0.3 V for more than 30 µs-signaling loss of valid RS-232 signal. It goes high when |RIN| exceeds ±2.7 V or transitions through the invalid window rapidly. This enables firmware to detect cable disconnects or bus faults without polling RIN voltage, improving system responsiveness.

Is the MAX3221CDBR compatible with 5-V logic inputs while operating from a 3.3-V supply?

Yes, the MAX3221CDBR accepts 5-V-tolerant logic inputs on DIN, FORCEON, FORCEOFF, and EN pins when powered from a 3.3-V VCC supply. Input voltage ratings extend to 5.5 V, allowing direct connection to 5-V microcontrollers or level-shifter outputs without external resistors-simplifying mixed-voltage system design and reducing component count.