MAX3320BCAP+

Overview

The MAX3320BCAP+ is a true RS-232 transceiver with an integrated power-on reset circuit, manufactured by Analog Devices Inc./Maxim Integrated. It operates on a single +3V to +5.5V supply and supports data rates up to 250kbps. The device features AutoShutdown Plus technology, achieving a low shutdown supply current of 4µA. It includes two receivers and two transmitters in a 20-pin SSOP package. The 'B' suffix indicates a reset threshold voltage of 2.85V. Operating temperature range is 0°C to +70°C.

Feature Summary

• Integrates a microprocessor supervisory circuit that asserts a reset signal when the VCC supply voltage declines below a preset threshold.
• Features proprietary low-dropout transmitter output stage enabling true RS-232 performance from a dual charge pump powered by a single supply.
• Includes AutoShutdown Plus functionality that reduces supply current to 4µA when receiver and transmitter inputs remain inactive for 30 seconds.
• Provides an active-low RESET output guaranteed to be in the correct state down to VCC = 1V.

Applications

• Palmtop Computers
• Portable/Battery-Powered Equipment
• Hand-Held Equipment

Procurement Notes

Verify the specific ordering suffix against the datasheet table to confirm the reset threshold voltage matches the design requirement. Ensure the component is sourced from authorized distributors to guarantee authenticity and compliance with RoHS standards. Check the operating temperature range specifications to ensure suitability for the intended environmental conditions.

Selection Notes

Select this component when a combined RS-232 interface and power-supply monitoring solution is required for space-constrained designs. The 'B' variant provides a 2.85V reset threshold, suitable for 3.3V logic systems. Consider the 250kbps maximum data rate and the need for external charge-pump capacitors during system architecture planning.

Part Context

This part belongs to the MAX3320A/B/L/T family of RS-232 transceivers. The family shares identical electrical characteristics and pinouts but differs in the reset threshold voltage determined by the ordering suffix. All variants utilize the same 20-pin SSOP package and support the same data rates and power management features.

Replacement Considerations

Direct replacements within the same series include MAX3320ACAP+, MAX3320LCAP+, and MAX3320TCAP+. These parts share identical functionality but offer different reset threshold voltages (4.25V, 4.63V, and 3.08V respectively). Verify that the alternative reset threshold aligns with the target system's power supply levels.

FAQ

What is the function of the INVALID output?

The INVALID output asserts high when no valid RS-232 levels are present on any of the receiver inputs for at least 90µs. It can be used to indicate DTR or Ring Indicator signals.

How does AutoShutdown Plus operate?

AutoShutdown Plus monitors receiver and transmitter inputs. If all inputs remain inactive for more than 30 seconds, the internal power supply and drivers shut off, reducing the supply current to 4µA. The device wakes up upon detecting a valid transition on any input.

What is the reset threshold voltage for the MAX3320BCAP+?

The 'B' suffix indicates a reset threshold voltage of 2.85V. The RESET output remains low while VCC is below this threshold and stays asserted for at least 100ms after VCC rises above it.