Analog Devices Inc./Maxim Integrated MAX6309UK44D3-T

Overview

MAX6309UK44D3-T from Maxim Integrated is a 5-pin SOT23 programmable supervisory IC that monitors VCC (factory-set to 4.4V ±2.5%), an adjustable undervoltage input (RST IN), and a manual-reset input (MR) to assert an active-low push/pull RESET output. It guarantees valid reset down to VCC = 1V, features 140ms minimum reset timeout, and draws only 8µA supply current - ideal for multivoltage embedded systems requiring reliable power-on and brownout reset in portable equipment.

For engineers reviewing the MAX6309UK44D3-T datasheet, MAX6309UK44D3-T pinout, MAX6309UK44D3-T application, or MAX6309UK44D3-T equivalent, key selection considerations include its factory-trimmed 4.4V VCC threshold, 140ms timeout (D3), push/pull RESET drive capability, MR input with internal 63.5kΩ pull-up, and immunity to fast VCC transients up to 280µs at 4.4V overdrive.

Technical Context

The MAX6309UK44D3-T implements a dual-monitoring architecture: a factory-trimmed internal voltage divider sets the primary VCC reset threshold at 4.4V, while a separate comparator monitors the RST IN pin against a 1.23V reference for external undervoltage detection. Its push/pull RESET output sources/sinks current (VOH = 0.8×VCC, VOL = 0.3V), eliminating external pull-up components.

Reset assertion occurs when VCC falls below 4.4V × (1 − 2.5%) or RST IN drops below 1.23V, with hysteresis of 2.5mV on RST IN and 2×VTH mV on VCC. The internal timer enforces a guaranteed minimum 140ms reset pulse after all monitored supplies recover, and MR input forces reset with <1.5µs minimum pulse width and glitch rejection of 0.1µs.

Key Specifications

Pinout & Package

MAX6309UK44D3-T is housed in a 5-pin SOT23 package (outline U5+1, footprint 90-0174), optimized for space-constrained PCB layouts and reflow-compatible assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar supervisory applications.

Compared with MAX6309UK44D3-T, the MAX6309UK46D3-T offers a higher VCC trip point for margin-critical 5V designs, while the TPS3808G33DBVR reduces quiescent current by >80% but sacrifices dual-supply monitoring and manual reset - making it suitable only for simpler, single-rail use cases.

Availability

MAX6309UK44D3-T is available at Aetrix Electronics and suitable for portable computers, industrial PLCs, and battery-powered data loggers requiring stable component supply across commercial temperature range and long production lifecycles.

Supply support for MAX6309UK44D3-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) designs precision analog and mixed-signal ICs for power management, sensing, and interface applications in industrial, computing, and medical markets.

The MAX6305–MAX6313 family was developed to provide compact, low-power, multi-input supervisory solutions for multivoltage embedded systems - specifically addressing the need for factory-programmable thresholds, transient-immune reset generation, and flexible manual/external reset control in space-constrained designs.

FAQ

What is the exact factory-programmed VCC reset threshold for MAX6309UK44D3-T?

The MAX6309UK44D3-T has a factory-trimmed VCC reset threshold of 4.4V with ±2.5% tolerance over the 0°C to +70°C operating range. This value is permanently laser-trimmed during manufacturing and corresponds to the "44" in the part number per Table 1 of the datasheet. It is designed to supervise standard 5V power rails while allowing margin for ripple and tolerance.

Does MAX6309UK44D3-T require external components to function as a basic VCC supervisor?

No, MAX6309UK44D3-T operates as a complete VCC supervisor without external components: its 4.4V threshold is factory-programmed, the 140ms reset timeout is internally generated, and the push/pull RESET output drives loads directly. Only optional components - such as a momentary switch on MR or a resistor divider on RST IN - are needed for extended functionality beyond basic 5V rail monitoring.

How does the manual reset (MR) input behave on MAX6309UK44D3-T?

On MAX6309UK44D3-T, the MR input is active-low with an internal 63.5kΩ pull-up resistor. Pulling MR low asserts RESET immediately and holds it active for the full 140ms timeout period after MR returns high. The input accepts TTL/CMOS logic levels and rejects glitches shorter than 0.1µs, enabling reliable reset initiation via simple switch or logic signal without external debounce circuitry.

Can MAX6309UK44D3-T monitor a 3.3V supply in addition to its 4.4V VCC input?

Yes, MAX6309UK44D3-T can monitor a 3.3V supply using its RST IN pin. By connecting a resistor divider from the 3.3V rail to RST IN and ground, the input voltage is scaled to fall below the 1.23V internal reference when the 3.3V rail drops out of regulation. This enables dual-supply supervision - e.g., 5V (VCC) and 3.3V (RST IN) - within a single SOT23-5 device.

What is the minimum VCC voltage at which MAX6309UK44D3-T guarantees valid RESET output?

MAX6309UK44D3-T guarantees valid RESET output down to VCC = 1.0V. Below this, the push/pull output's sourcing/sinking capability degrades, but between 1.0V and 5.5V, RESET remains a well-defined logic low (≤0.3V) or high (≥0.8×VCC) signal. This ensures deterministic microprocessor reset behavior even during severe brownout conditions before complete power collapse.