MAX232NS - 2/2 RS-232 Transceiver, 120 kbps | Texas Instruments
MPN: MAX232NS ✓ ActiveMAX232NS Overview
An RS-232 transceiver is an interface IC within the broader transceiver and interface IC hierarchy. It bridges the voltage-domain difference between a modern digital system and a legacy RS-232 port. The MAX232NS includes an on-chip capacitive voltage generator, so the external circuit requires the specified charge-pump capacitors rather than a separate negative supply. This integration makes it suitable for equipment with a single positive supply rail.
Key features include two transmit channels, two receive channels, a 120 kbps maximum data rate, and receiver hysteresis of 500 mV. According to the Texas Instruments datasheet SLLS047N, the receivers have a typical threshold of 1.3 V and can accept input voltages of ±30 V. The device operates from 4.5 V to 5.5 V and is offered here in the commercial-temperature 0 °C to 70 °C range.
Technically, the transmitters convert TTL/CMOS inputs into RS-232 levels, while the receivers perform the inverse conversion. The integrated voltage generator produces the bipolar voltage required for RS-232 signaling from the 5 V supply. Receiver hysteresis helps reject noise around the input switching threshold, improving reliability on connections that may pick up interference. The dual-channel arrangement supports two independent RS-232 directions on one board.
Typical uses include serial adapters, industrial control links, service equipment, data-acquisition systems, and legacy computer or peripheral connections. A transmit-and-receive pair can support one full-duplex RS-232 port, while the second channel can serve another port or provide an additional direction. The 16-pin SOIC package supports conventional surface-mount PCB assembly and standard automated production lines.
The principal design consideration is charge-pump capacitor selection and placement. Use the capacitor values specified by the manufacturer and keep the associated traces short, because long or poorly routed paths can degrade startup behavior and increase supply transients. The supply must also remain within 4.5 V to 5.5 V, and exposed RS-232 inputs require protection appropriate to the installation environment.
This page consolidates the verified manufacturer specifications, RS-232 application guidance, source links, and same-package replacement information. It is designed to help engineers identify the correct electrical limits, package, procurement data, and design considerations without relying on assumptions about unverified parameters.
Drop-in alternatives for MAX232NS — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with MAX232NS (same form factor and footprint) — differing in Package, Data Rate, Function, Operating Temperature, Supply Voltage (Vcc).
MAX232DR
✅ Drop-InContact for price
View Datasheet →MAX232ESE
✅ Drop-In📋 Reference alternative (not in catalog)
MAX232AESE
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MAX232CSE+T
✅ Drop-In ⚠️ Specs UnverifiedContact for price
View Datasheet →ST232BDR
✅ Drop-In📋 Reference alternative (not in catalog)
MAX232NS Specifications
| Product Type | RS-232 dual transceiver |
| Number of Drivers | 2 |
| Number of Receivers | 2 |
| Maximum Data Rate | 120 kbps |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Typical Receiver Threshold | 1.3 V |
| Receiver Hysteresis | 500 mV |
| Maximum Receiver Input Voltage | ±30 V |
| Operating Temperature | 0 °C to 70 °C (TA) |
| Package | 16-pin SOIC, 0.209-inch body width |
| Mounting Type | Surface mount |
| Integrated Voltage Generator | Yes, capacitive charge-pump voltage generator |
| Supported Supply Configuration | Single 5 V supply |
| Logic Interface | TTL/CMOS |
| Signal Standard | TIA/EIA-232-F |
MAX232NS Pin Configuration
| Pin 1 | R1OUT — Receiver 1 output |
| Pin 2 | R1IN — Receiver 1 input |
| Pin 3 | R2IN — Receiver 2 input |
| Pin 4 | R2OUT — Receiver 2 output |
| Pin 5 | T2IN — Transmitter 2 logic input |
| Pin 6 | T1IN — Transmitter 1 logic input |
| Pin 7 | GND — Ground |
| Pin 8 | VCC — Positive supply |
| Pin 9 | T1OUT — Transmitter 1 RS-232 output |
| Pin 10 | T2OUT — Transmitter 2 RS-232 output |
| Pin 11 | VEE — Negative voltage generated output |
| Pin 12 | C2+ — Charge-pump capacitor 2 positive terminal |
| Pin 13 | C2- — Charge-pump capacitor 2 negative terminal |
| Pin 14 | C1+ — Charge-pump capacitor 1 positive terminal |
| Pin 15 | C1- — Charge-pump capacitor 1 negative terminal |
| Pin 16 | VCC — Positive supply |
Typical Applications
MAX232NS is suitable for 6 applications: Legacy Computer Serial Port Interface, Industrial Control and Service Console, Data-Acquisition Equipment Interface, Serial Adapter and Dongle, Embedded Controller Communication, Networking and Communication Equipment.
Legacy Computer Serial Port Interface
The MAX232NS fits legacy computer and peripheral ports because it converts two logic-level channels into RS-232 levels and converts two received RS-232 channels back to TTL/CMOS. Its 120 kbps maximum data rate covers many COM-port baud rates, while the 16-pin SOIC package simplifies assembly on a modern mixed-signal PCB. The integrated charge-pump generator eliminates a separate negative supply, and the 500 mV receiver hysteresis helps reject noise near the logic switching threshold.
Recommended
Industrial Control and Service Console
MAX232NS is useful in industrial control panels and service consoles where a controller communicates with older RS-232 equipment. The 2/2 driver and receiver arrangement allows one channel pair to form a full-duplex link while leaving another channel available for a second peripheral or diagnostic connection. The device supports 120 kbps and operates from one 4.5 V to 5.5 V rail, but its specified 0 °C to 70 °C range must be checked against the enclosure environment.
Recommended
Data-Acquisition Equipment Interface
The MAX232NS can connect laboratory instruments, analyzers, and data-logging equipment that retain an RS-232 command interface. Its receivers tolerate inputs up to ±30 V, which is useful when the connected line experiences transient overshoot, while the typical 1.3 V threshold and 500 mV hysteresis improve noise immunity. At rates up to 120 kbps, engineers can use the two channels for separate control and measurement paths while keeping external power requirements simple.
Recommended
Serial Adapter and Dongle
A compact serial adapter can use the MAX232NS to bridge a low-voltage UART controller to a legacy RS-232 connector. The 16-pin SOIC package preserves board area compared with larger through-hole arrangements, and the integrated voltage generator avoids a separate negative rail that would complicate portable or embedded systems. Designers should provide the manufacturer-specified charge-pump capacitors, a suitable connector protection scheme, and grounding appropriate to the cable environment.
Recommended
Embedded Controller Communication
The MAX232NS suits embedded systems that expose a service, configuration, or diagnostics port using RS-232. It requires only a single positive 5 V supply and can pair with a microcontroller UART at logic levels, eliminating the need for a separate negative regulator. Its 120 kbps capability is suitable for configuration commands and moderate diagnostic traffic, although the application should not expose the transceiver pins directly to user-controlled cables without ESD and surge protection.
Recommended
Networking and Communication Equipment
MAX232NS is applicable to communication equipment that retains a short RS-232 management or point-to-point link. The dual transmitters and dual receivers provide flexible channel allocation, and the single-supply charge-pump implementation simplifies system power architecture. Its commercial 0 °C to 70 °C rating supports controlled indoor environments, while the receiver's ±30 V tolerance and 500 mV hysteresis add margin on older installations. Longer cables or electrically noisy locations still require careful grounding and connector protection.
Recommended
Recommended Products Summary
Engineering reference data for MAX232NS — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX232DR | MAX232ESE | MAX232AESE | MAX232CSE | ST232BDR |
|---|---|---|---|---|---|---|
| Package | 16-pin SOIC | 16-pin SOIC - same | 16-pin SOIC - same | 16-pin SOIC - same | 16-pin SOIC - same | 16-pin SOIC - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | STMicroelectronics |
Key Differentiators
- Preferred internal-link replacement source (vs MAX232DR)
- Single-supply RS-232 conversion (vs ST232BDR)
- Receiver noise margin (vs ST232BDR)
- Documented commercial-temperature configuration (vs MAX232AESE)
Design Notes
Place the four charge-pump capacitors directly beside their associated MAX232NS pins and keep their connection traces short. Use the capacitor values and tolerances specified by Texas Instruments datasheet SLLS047N. A compact placement minimizes switching-loop area and limits supply disturbance during RS-232 line transitions. Route the pins sequentially around the package where practical, and avoid interposing long traces or test pads that increase capacitive loading.
Do not assume that every MAX232-family ordering code is an automatic drop-in replacement. MAX232NS is specified for 4.5 V to 5.5 V, 0 °C to 70 °C, 120 kbps, and a 16-pin SOIC. Before using MAX232DR, MAX232ESE, MAX232AESE, MAX232CSE, or ST232BDR, compare the exact pin assignment, external capacitor values, supply current, driver slew rate, receiver timing, ESD rating, and temperature grade.
Keep the transceiver's logic-side traces away from the RS-232 connector and cable entry point, and provide a direct ground-return path from the board ground to the connector shell or chassis ground. The receiver's 500 mV hysteresis improves noise rejection, but it does not replace good signal-integrity layout. Use appropriate series resistance or protection at externally accessible connector pins when the installation permits electrostatic discharge or surge events.
Decouple the 5 V supply close to pins 8 and 16 using the capacitance and placement required by the manufacturer. The charge-pump generator produces current pulses when the transmitter changes state, so the local supply network must maintain low impedance during those transitions. Verify the design across maximum line load, temperature, and cable conditions rather than relying only on the nominal quiescent supply current.
Compliance Information
The supplied verified excerpts identify the manufacturer, electrical characteristics, package, operating temperature, and active status but do not explicitly state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status. These fields remain unknown rather than inferred.
