Analog Devices Inc./Maxim Integrated MAX8881EUT50

MAX8881EUT50 Fixed 5V Linear Regulator Product Summary

The MAX8881EUT50, designed by Analog Devices Inc./Maxim Integrated, is a positive fixed output linear voltage regulator optimized for battery-powered and low power applications. Housed in a compact SOT23-6 package, the MAX8881EUT50 delivers a regulated 5V output at up to 200mA of load current with exceptional power efficiency thanks to its ultra-low quiescent current operation. This device is particularly well-suited for handheld instruments, portable systems, and applications where reverse battery protection and long battery runtime are key priorities.

Main Features of the MAX8881EUT50

The MAX8881EUT50 incorporates an array of features tailored to maximize battery life and ensure reliable operation in power-sensitive designs:

Ultra-low quiescent current of 3.5μA at 12V input, extending battery operating time, especially during standby.

Wide input range from 2.5V to 12V, allowing compatibility with a variety of power sources, including single or multiple cell batteries.

Fixed 5V regulated output voltage with ±1.5% accuracy, reducing tolerance stack-ups in precision systems.

Capable of supplying up to 200mA output current—sufficient for a variety of small loads and core system support circuits.

Integrated power-OK (POK) open-drain output for monitoring output regulation status.

Reverse battery protection, output short-circuit protection, and thermal-overload shutdown integrated, essential for robustness in uncontrolled field environments.

Packaged in a space-saving SOT23-6 (as well as thin TDFN packages in the series), suitable for dense PCB layouts or space-constrained hardware.

MAX8881EUT50 Operation and Functional Principle

At the heart of the MAX8881EUT50 is a 2Ω P-channel MOSFET pass transistor, controlled by a precision error amplifier driven from a 1.25V internal reference. The regulator’s design eliminates the excess base-drive currents characteristic of legacy PNP-based LDOs, yielding greater efficiency at both low and high load currents and maintaining low quiescent current at all times.

The regulator continuously compares a fraction of its output voltage (via a precision internal resistor divider) to the reference. When deviations are detected, the error amplifier adjusts the gate of the MOSFET to maintain the output at a steady 5.0V within tight tolerance limits. The inclusion of an open-drain POK output allows for easy interfacing to system reset or fault monitoring circuits, flagging when the output falls more than 10% below its nominal value.

Protection Mechanisms and Reliability of the MAX8881EUT50

Engineers specifying the MAX8881EUT50 will find several integrated protection features crucial for increasing system robustness:

Reverse Battery Protection: The LDO disconnects internal circuitry when VIN polarity is reversed (VIN < 0V), restricting reverse current to less than 1mA. This safeguards both the regulator and downstream circuitry from inadvertent miswiring or battery reversal.

Output Short-Circuit Protection: The regulator’s PMOS pass device is current-limited under fault conditions, allowing the output to be shorted to ground indefinitely without damage—a valuable safeguard for in-field reliability.

Thermal Overload Protection: Should the internal junction temperature exceed 160°C, the regulator self-protects by shutting down until safe temperatures resume. This cycling prevents permanent damage under thermal stress, adding another layer to the device’s defensive architecture.

Electrical Specifications and Performance Data for the MAX8881EUT50

Operating over -40°C to +85°C, the MAX8881EUT50 boasts:

Output Voltage: Factory-preset to 5V; accuracy ±1.5%.

Maximum Output Current: 200mA continuous.

Dropout Voltage: Defined primarily by RDS(ON) of 2Ω; for example, at 200mA, the typical dropout is 400mV, ensuring operation from low headroom battery voltages.

Power Supply Rejection: 66dB at low frequency, with roll-off above 100Hz; performance can be maximized by careful output capacitor selection.

Stability: Designed to be stable with ceramic capacitors as low as 1μF and output ESR up to 1Ω.

Supply Current: Only 3.5μA, minimizing wasted energy in always-on and long-standby designs.

Absolute Maximum Ratings: VIN from -14V to +14V, output current up to 200mA, with robust handling of transient fault conditions.

Common Engineering Uses for the MAX8881EUT50

The MAX8881EUT50 is particularly well-suited for battery-powered portable devices, handheld meters and instrumentation, small-scale sensor node power supplies, and consumer or industrial electronics where board real estate and power budgets are at a premium.

For example, in a battery-operated wireless sensor, the MAX8881EUT50 can provide the noise-sensitive logic supply while drawing virtually no power during system sleep states. In such designs, its POK output can be used to gate a microcontroller’s reset signal, improving system startup diagnostics and reducing firmware complexity.

MAX8881EUT50 Design Guidelines and Implementation Advice

Input and Output Capacitor Selection: For stable operation across temperature and load current, use a 4.7μF X7R or X5R ceramic capacitor at the output and a minimum 1μF at the input. The output capacitor ESR should remain under 1Ω; higher values and lower ESR improve transient response and noise rejection.

PCB Layout: Minimize trace lengths from the regulator’s input and output pins to the corresponding capacitors, especially in high-speed or noisy environments. Good thermal management should be considered, ensuring adequate copper area to assist in heat dissipation.

POK Output Usage: Tie the POK output to the positive rail through a high-value resistor for error flagging. An RC delay network can add a startup or fault-clearing delay, suitable for sequencing or system-level reset timing.

Power Dissipation: Maximum power dissipation is given by the difference between VIN and VOUT times output current, limited by the thermal resistance of the chosen package and the PCB layout. Ensure the junction temperature does not continuously exceed 150°C.

Shut Down Control: The SHDN (shutdown) pin allows manual control; driving SHDN low disables the output and minimizes supply current for aggressive power savings in standby or sleep modes.

Mechanical Specifications and Packaging Information for the MAX8881EUT50

The MAX8881EUT50 is supplied in a 6-pin SOT23 package, with all dimensions conforming to JEDEC MO178, Variation AB. This footprint supports automated SMT assembly and is suitable for high-density board layouts. For applications with stricter height or thermal requirements, thin 6-pin TDFN package versions of the MAX8881 series are also available. Dimensional details, lead finish specifications, and coplanarity limits follow standard industry conventions, ensuring mechanical compatibility with most modern SMT process lines.

Alternative or Substitute Models for the MAX8881EUT50

When evaluating the MAX8881EUT50 for new or replacement designs, engineers may consider products in the same MAX8881 series with different output voltages (such as MAX8881EUT18/25/33 for 1.8V, 2.5V, and 3.3V). For applications requiring adjustable outputs, the closely related MAX8880 enables voltage setting via external resistors. In cases where the MAX8881EUT50’s supply or load specifications are not met, alternative industry-standard low-dropout linear regulators with similar ultra-low quiescent current and small package footprints may be compared, but care must be taken to match critical features such as output voltage accuracy, dropout voltage, and protection characteristics.

Conclusion

The MAX8881EUT50 from Analog Devices Inc./Maxim Integrated offers an ideal balance of ultra-low quiescent current, robust protection, and precise fixed 5V regulation in a small form factor. Its feature set targets demanding battery-powered and portable electronic designs, helping engineers maximize system uptime and reliability through best-in-class supply current and integrated safety features. The MAX8881EUT50’s adaptability, ease of use, and high integration make it a strong candidate for new power supply designs where energy efficiency and performance are key metrics. Whether for replacement or new design, this device provides a technically sound, rugged, and efficient solution for modern low-power applications.