MAX3218CPP

Overview

The MAX3218CPP+ is a dual-driver, dual-receiver RS-232 transceiver designed for battery-powered EIA/TIA-232E and V.28/V.24 interfaces. It operates from a single +1.8V to +4.25V supply without external voltage regulators. The device features an AutoShutdown™ function that reduces supply current to 1µA when no valid signal is detected. It guarantees a data rate of 120kbps and maintains true RS-232 and EIA/TIA-562 voltage levels. The component is housed in a 20-pin Plastic DIP package and supports an operating temperature range of 0°C to +70°C.

Feature Summary

• AutoShutdown technology minimizes power consumption by disabling the onboard DC-DC converter and drivers when invalid receiver input levels are sensed.
• Integrated switch-mode power supply generates required ±6.5V rails using minimal external components including one inductor, one diode, and three capacitors.
• Three-state receiver outputs allow multiple receivers with different interface standards to be wire-ORed on the same bus.
• Flow-through pinout facilitates printed circuit board layout.

Applications

• Battery-powered equipment
• Subnotebook computers
• Personal Digital Assistants (PDAs)
• Hand-held equipment
• Peripherals

Procurement Notes

Verify the specific ordering suffix to confirm the package type and temperature rating. The 'CPP' designation indicates a 20-pin Plastic DIP package with a commercial temperature range of 0°C to +70°C. Ensure the '+'' suffix is present to confirm lead-free and RoHS compliance status as defined in the manufacturer's ordering information.

Selection Notes

Select this component for applications requiring low-power RS-232 communication directly from two alkaline, NiCd, or NiMH cells. It is suitable where system software cannot be modified to manage power states, as the AutoShutdown feature operates automatically based on receiver input signals. Verify that the load capacitance requirements align with the guaranteed 120kbps data rate specifications.

Part Context

The MAX3218 belongs to Maxim Integrated's family of low-voltage RS-232 transceivers. It shares functional similarities with the MAX218 but offers extended supply voltage compatibility down to 1.8V. The device utilizes proprietary CMOS technology to achieve significantly lower quiescent currents compared to traditional bipolar RS-232 drivers.

Replacement Considerations

MAX218: Similar functionality with AutoShutdown but limited to higher minimum supply voltages.

FAQ

How does the AutoShutdown feature determine when to enter low-power mode?

The device enters shutdown mode when it senses no valid RS-232 signal level on either receiver input for typically 30µs. This occurs if the cable is disconnected or peripheral transmitters are off.

Can the receivers remain active while the transmitters are shut down?

Yes, during AutoShutdown, both receivers can remain active to monitor external devices, or they can be disabled under logic control via the FORCEON and FORCEOFF pins.

What external components are required for the onboard DC-DC converter?

The circuit requires one 15µH inductor, one fast recovery diode (e.g., 1N6050), and three capacitors (C1=0.47µF, C2=1µF, C3=1µF) plus a bypass capacitor at VCC.