Low Voltage RS-232 Interface Chips Get Tough With ESD

Powered from as little as 3V, the ST3243E RS-232 transceiver and ST3232E multiple RS-232 driver/receiver chips are rated at a minimum transfer rate of 250 Kb/s and are said to provide rugged ESD protection. The ST3243E includes three drivers and five receivers and the ST3232E two drivers and two receivers. Each I/O pin of both devices is protected to ±15 kV using the human body model and ±8 kV via the IEC 1000-4-2 contact discharge method. Both chips also include a dual charge-pump circuit, allowing the devices to meet EIA/TIA-232 specs while operating from a 3V to 5.5V supply voltage. Other common features include a 6V/µs slew rate and an operational temperature range from -40°C to +85°C or 0°C to 70°C. The ST3243E includes an automatic power-down function that cuts supply current consumption to as low as 1 µA. During this mode of operation, drivers and receivers are turned off in the absence of signals. The ST3232E limits supply current to 300 µA and provides a typical output voltage swing of ±5.4V with all lines loaded, a receiver input voltage range of ±25V, and a typical propagation delay input-to- output of 0.15 µs. The ST3243E RS-232 is available in TSSOP-28, SSOP-28, SO-28, and flip-chip packages and the ST3232E RS-232 in TSSOP-16, SO-16, SO-16, and DIP-16 packages. Prices range from $0.80 to $1.00 each/1,000. STMICROELECTRONICS INC., Lexington, MA. (781) 861-2650.