The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated EIA/TIA-232 and V.28/V.24 communications interface with high data-rate capabilities. The MAX3250 is a dual die part that operates with up to ±50V difference between the RS-232 side and the logic side (ISOCOM to GND). This makes the device ideal for operation in noisy conditions with high common-mode voltages. This feature prevents damage to the device if RS-232 lines are inadvertently short-circuited to a +24V or ±48V power bus. The MAX3250 is powered by a single 3V to 5.5V supply on the logic side. Power is transferred from the logic side to the isolated side by ±100V external capacitors. The MAX3250 has two receivers (Rx) and two drivers (Tx) and is guaranteed to run at data rates of 250kbps while maintaining RS-232 output levels. The trans- ceivers have a proprietary low-dropout transmitter out- put stage, delivering true RS-232 performance from a 3V to 5.5V supply with a dual charge pump. The device features a FAULT open-drain output to signal an exces- sive isolated-side voltage condition on any of the RS- 232 inputs. This output can drive an alarm LED or can be monitored by the processor to prevent operation under these conditions. The receiver outputs are high impedance in shutdown, allowing multiple interfaces (IrDA, RS-232, RS-485) to be connected to the same UART. The MAX3250 is available in a space-saving 28-pin SSOP package. Applications Industrial Control Programmable Logic Controller Point-to-Point Communication Data Acquisition
The MAX3250 is a +50 V isolated EIA/TIA‑232 and V.28/V.24 communications interface that operates from a 3.0 V to 5.5 V supply. It provides two transmitters and two receivers, guarantees 250 kbps data rates, and includes a FAULT open‑drain output for over‑voltage protection. The device is supplied in a space‑saving 28‑pin SSOP package and is intended for noisy industrial environments, point‑of‑sale equipment, telecom gear and other applications requiring high common‑mode voltage isolation.
Key features include indeterminate‑/transformer‑less isolation, low‑power shutdown (≈20 µA), high‑impedance outputs in shutdown, and a dual charge‑pump voltage converter that generates ±5.5 V on the isolated side. The datasheet provides detailed electrical characteristics, timing specifications, recommended capacitor values, layout guidelines, and ordering information.
| Isolation Voltage | +50 V |
|---|---|
| Supply Voltage (logic side) | 3.0 V to 5.5 V |
| Data Rate | 250 kbps (guaranteed) |
| Drivers / Receivers | 2 Tx, 2 Rx |
| Shutdown Supply Current | ≈20 µA |
| Operating Temperature Range | -40 °C to +85 °C (MAX3250EAI) |
| Package | 28‑pin SSOP |
| Isolation Resistance | 60 kΩ |
| Fault Output | Open‑drain, active low |
The device provides up to +50 V isolation between the RS‑232 side and the logic side.
In shutdown the MAX3250 draws about 20 µA of supply current.
The MAX3250 is offered in a 28‑pin SSOP package.
The transceiver is guaranteed to operate at 250 kbps.