MAX3238E

The MAX3238E/MAX3248E transceivers use Maxim's revolutionary AutoShutdown Plus™ feature to achieve 10nA supply current. These devices shut down the onboard power supply and drivers when they do not sense a valid signal transition on either the receiver or transmit- ter inputs. This occurs if the RS-232 cable is disconnected or if the transmitters of the connected peripheral are turned off. The devices turn on again when a valid transition is applied to any RS 232 receiver or transmitter input.

AutoShutdown Plus automatically achieves this power savings through its on-board circuitry, as no changes are required to the existing BIOS or operating system. All RS-232 inputs and outputs, as well as the logic I/O pins, have enhanced ESD protection to ±15kV. The additional ESD protection on the logic I/O pins makes the MAX3238E/MAX3248E ideal for cell phone data cable applications because it eliminates the need for costly external TransZorb™or protection schemes.

The MAX3238E/MAX3248E contain five drivers and three receivers and are 3V-powered EIA/TIA-232 and V.28/V.24 communication interfaces intended for cell phones, datacables, and modem applications. A proprietary, high-efficiency, dual charge-pump power supply and a low-dropout transmitter combine to deliver true RS-232 performance from a single +3.0V to +5.5V supply. A guaranteed data rate of 250kbps provides compatibility with popular software for communicating with personal computers. The MAX3238E and the MAX3248E differ only in their input logic thresholds. The MAX3238E has standard logic thresholds, while the MAX3248E has low-level logic thresholds of 0.6V to 1.2V, which are ideal for 1.8V systems.

The transmitter inputs, FORCEON, and FORCEOFF have a 400kΩ active positive feedback resistor. Once driven to a valid logic level, they will retain this level if the driving signal is removed or goes high impedance. Unused transmitter and logic inputs may be left unconnected. The MAX3238E/MAX3248E can operate with supply voltages ranging from +3.0V to +5.5V.