Analog Devices Inc./Maxim Integrated MAX6328UR28-T

Overview

MAX6328UR28-T from Maxim Integrated is an open-drain, active-low microprocessor supervisory circuit in SOT23-3 package, designed to monitor 2.8V power supplies and assert reset when VCC falls below 2.800V (±2.5% over temperature), with ≥100ms reset timeout after recovery. It draws ≤1µA supply current and operates from -40°C to +85°C, supporting portable/battery-powered µP systems.

For engineers reviewing the MAX6328UR28-T datasheet, MAX6328UR28-T pinout, MAX6328UR28-T application, or MAX6328UR28-T equivalent, key selection criteria include open-drain output compatibility with bidirectional µP reset pins (e.g., Motorola 68HC11), factory-trimmed 2.8V threshold with 40ppm/°C tempco, 100ms min reset timeout, and immunity to VCC transients up to 200µs at 100mV overdrive.

Technical Context

The MAX6328UR28-T implements a precision bandgap-based voltage comparator with hysteresis (6.3mV) to detect VCC drops below its 2.800V threshold, asserting an open-drain RESET signal that remains low for ≥100ms after VCC rises above threshold. Its internal timing circuit ensures consistent reset pulse width across temperature.

Designed for direct interface with microcontrollers having bidirectional reset pins, the open-drain output requires only a single external pull-up resistor. The device ignores fast negative-going VCC transients-up to 200µs duration at 100mV overdrive-preventing false resets during noise events.

Key Specifications

Pinout & Package

MAX6328UR28-T is housed in a 3-pin SOT23-3 package (outline U3-1), with 1.3mm × 2.9mm footprint and 0.95mm height, suitable for high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor reset supervision applications.

Compared with MAX809TRD29+T and TPS3808G12QDBVRQ1, the MAX6328UR28-T provides optimal trade-off for portable and industrial embedded systems requiring factory-set 2.8V monitoring, open-drain flexibility, and sub-1µA operation-without added passives or qualification overhead.

Availability

MAX6328UR28-T is available at Aetrix Electronics and suitable for battery-powered IoT sensors, industrial PLC modules, medical wearables, and automotive BCM subsystems requiring stable component supply and long-term lifecycle support.

Supply support for MAX6328UR28-T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and consumer applications.

The MAX6326/MAX6327/MAX6328 family was engineered specifically for ultra-low-power microprocessor supervision in space-constrained, battery-sensitive systems-emphasizing precision threshold accuracy, minimal current draw, and robust transient immunity.

FAQ

What is the exact reset threshold voltage of MAX6328UR28-T and how does it vary with temperature?

The MAX6328UR28-T has a nominal reset threshold of 2.800V at +25°C, with guaranteed tolerance of ±2.5% over the full -40°C to +85°C operating range. Its temperature coefficient is 40ppm/°C, meaning threshold drift is limited to approximately ±11.2mV across the entire temperature span-ensuring stable brownout detection in industrial environments where the MAX6328UR28-T is deployed.

Does MAX6328UR28-T require an external pull-up resistor on the RESET pin, and why?

Yes, MAX6328UR28-T requires an external pull-up resistor on the RESET pin because it features an open-drain output. This architecture allows multiple devices-including other supervisors or µPs-to share the same reset bus without contention. The pull-up value (typically 10kΩ to 100kΩ) must be selected based on bus capacitance and rise-time requirements; omission would leave RESET floating and non-functional. This design choice is intrinsic to the MAX6328UR28-T's interoperability with bidirectional reset interfaces.

Can MAX6328UR28-T operate reliably during deep brownout conditions, and what is its minimum functional VCC?

Yes, MAX6328UR28-T is guaranteed to maintain correct reset state down to VCC = 1.0V at room temperature and 1.2V across the full -40°C to +85°C range. This ensures the MAX6328UR28-T continues asserting RESET even as the supply collapses-preventing premature release of reset during undervoltage events. Its internal bandgap reference and comparator remain functional well below typical logic thresholds, making it suitable for fail-safe shutdown sequencing in critical systems.

How does MAX6328UR28-T handle short-duration power supply transients, and what is its immunity specification?

MAX6328UR28-T rejects fast negative-going VCC transients up to 200µs in duration when the overdrive (VTH − VCC) is 100mV, as verified in the Typical Operating Characteristics graph "Maximum Transient Duration vs. Reset Threshold Overdrive." This immunity prevents false resets caused by switching noise or coupling spikes, eliminating the need for external RC filters on the VCC rail-a key advantage of the MAX6328UR28-T in noisy industrial or automotive environments.

Is MAX6328UR28-T pin-compatible with legacy Maxim reset ICs like MAX803 or MAX809?

MAX6328UR28-T shares the same 3-pin SOT23-3 package and pinout (GND, RESET, VCC) as MAX803/MAX809/MAX810, enabling drop-in replacement in many designs. However, its open-drain output differs from the push-pull outputs of MAX809 variants-so existing pull-up resistors must remain, and shared-bus configurations may require validation. The MAX6328UR28-T's identical footprint and function make it a direct mechanical and electrical upgrade where open-drain behavior is acceptable or preferred.