Analog Devices Inc./Maxim Integrated MAX6309UK44D3+

Overview

MAX6309UK44D3+ from Maxim Integrated is a 5-pin SOT23 programmable supervisory circuit that monitors VCC (factory-set at 4.38V ±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 assertion 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 protection.

For engineers reviewing the MAX6309UK44D3+ datasheet, MAX6309UK44D3+ pinout, MAX6309UK44D3+ application, or MAX6309UK44D3+ equivalent, key selection criteria include its factory-trimmed 4.38V VCC threshold, MR-driven reset initiation, immunity to sub-1µs VCC transients, and compatibility with 3.3V/5V mixed-rail systems where deterministic reset timing and low quiescent current are critical.

Technical Context

The MAX6309UK44D3+ implements a dual-monitoring architecture: one internal factory-trimmed voltage divider sets the primary VCC reset threshold at 4.38V, while a separate comparator monitors the external RST IN pin against a 1.23V reference. Its push/pull RESET output actively drives low (VOL ≤ 0.3V at 1.2mA) and high (VOH ≥ 0.8×VCC), eliminating external pull-up components.

Reset assertion is triggered when either VCC falls below 4.38V (±2.5% over temperature) or RST IN drops below 1.23V, with built-in hysteresis (2.5mV) and glitch rejection (0.1µs). The 140ms timeout (D3 variant) is factory-programmed and stable across -40°C to +85°C, with <±1% variation over temperature per typical operating curves.

Key Specifications

Pinout & Package

MAX6309UK44D3+ is housed in a lead-free 5-pin SOT23 package (package code U5+1), measuring 2.9mm × 1.6mm × 1.1mm, with gull-wing leads optimized for automated PCB assembly and thermal performance in space-constrained designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6309UK46D3+, the MAX6309UK44D3+ offers a lower VCC trip point better aligned with typical 5V ±5% tolerances, while versus TPS3808G33DBVR it provides essential dual-supply monitoring and manual reset - making it irreplaceable in multivoltage systems requiring field-serviceable reset initiation.

Availability

MAX6309UK44D3+ is available at Aetrix Electronics and suitable for industrial PLCs, medical infusion pumps, automotive body control modules, and network routers requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MAX6309UK44D3+ 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 demanding industrial, automotive, and communications applications, with expertise in power management and reliability-critical supervision.

The MAX6305–MAX6313 family delivers programmable, multirail supervisory functions for systems requiring deterministic reset behavior across wide temperature ranges and noisy power environments - specifically targeting embedded controllers in safety-aware applications.

FAQ

What is the exact factory-set VCC reset threshold for MAX6309UK44D3+?

The MAX6309UK44D3+ has a factory-trimmed VCC reset threshold of 4.38V, specified with ±2.5% tolerance over the full operating temperature range (-40°C to +85°C). This value is confirmed in Table 1 of the datasheet and corresponds to the "44" suffix in the part number, which maps to the 4.38V nominal threshold per Maxim's ordering convention.

Does MAX6309UK44D3+ support manual reset functionality, and how is it implemented?

Yes, MAX6309UK44D3+ includes a dedicated MR (manual reset) input on pin 4. Pulling MR low forces an immediate reset assertion, which remains active for the full 140ms timeout period after MR returns high. The pin features an internal 63.5kΩ pull-up resistor, allowing direct connection to a normally-open momentary switch tied to ground - no external components are needed.

What is the purpose of the RST IN pin on MAX6309UK44D3+, and what voltage does it monitor?

The RST IN pin (pin 3) on MAX6309UK44D3+ is an adjustable undervoltage input referenced to an internal 1.23V comparator threshold. It allows monitoring of a secondary supply rail (e.g., 3.3V) using an external resistor divider. When the divided voltage at RST IN falls below 1.23V, the device asserts RESET - enabling dual-rail supervision in multivoltage systems.

Can MAX6309UK44D3+ operate reliably during fast VCC transients, and what is its immunity specification?

Yes, MAX6309UK44D3+ is specifically designed to ignore fast VCC transients. Per the Typical Operating Characteristics, it rejects negative-going glitches shorter than ~0.5µs at 4.38V threshold overdrive - verified by the "Maximum Transient Duration vs. VCC Reset Threshold Overdrives" graph. This immunity prevents false resets caused by switching noise or load transients in dense PCB layouts.

What package type and RoHS status does MAX6309UK44D3+ use?

MAX6309UK44D3+ is supplied in a lead-free 5-pin SOT23 package (outline 21-0057, land pattern 90-0174), indicated by the "+" suffix in the part number. It complies with RoHS Directive 2011/65/EU and is rated for reflow soldering at +260°C, making it suitable for modern automated assembly processes without lead contamination concerns.