This document introduces the MAX221E, a +5V powered single transmit/receive RS-232 and V.28 communications interface with automatic shutdown/wake-up features and high data rate capabilities. The MAX221E features enhanced electrostatic discharge (ESD) protection. Both the transmitter output and receiver input are protected to ±15kV using the IEC 1000-4-2 Air-Gap Discharge Method, to ±8kV using the IEC 1000-4-2 Contact Discharge Method, and to ±15kV using the Human Body Model. The MAX221E achieves a low 1µA supply current with Maxim’s revolutionary AutoShutdown™ feature. AutoShutdown saves power without changes to the existing BIOS or operating system by entering low-power shutdown mode when the RS-232 cable is dis- connected or when the transmitter of the connected peripheral is off. The MAX221E wakes up and drives the INVALID pin high when an active RS-232 cable is con- nected, signaling the host that a peripheral is connected to the communications port. The MAX221E is available in a 16-pin SSOP package as well as a 16-pin TSSOP that uses 50% less board space than a 16-pin SO.
The MAX221E is a +5 V powered, single‑channel RS‑232 and V.28 transceiver with an AutoShutdown function that reduces supply current to 1 µA when no valid RS‑232 signal is present. It offers robust ESD protection of up to ±15 kV (Human Body Model) and includes a dual charge‑pump voltage converter for generating both positive and negative supplies from a single 5 V input.
The datasheet provides absolute maximum ratings, electrical and timing characteristics, pin descriptions, package options (16‑pin TSSOP/SSOP), and application notes such as capacitor selection, power‑supply decoupling, and software‑controlled shutdown. Test circuits and loop‑back results illustrate performance up to 250 kbps data rates.
| Supply Voltage (VCC) | +5 V ±10% |
|---|---|
| Supply Current (AutoShutdown) | 1 µA |
| ESD Protection (HBM) | ±15 kV |
| Maximum Data Rate | 250 kbps |
| Operating Temperature Range | -40 °C to +85 °C |
The device draws only 1 µA supply current when AutoShutdown is active.
It provides ±15 kV protection under the Human Body Model, ±8 kV under IEC 1000‑4‑2 Contact Discharge, and ±15 kV under IEC 1000‑4‑2 Air‑Gap methods.
The transceiver supports up to 250 kbps data rate.