Analog Devices Inc./Maxim Integrated MAX6309UK31D3

Overview

The MAX6309UK31D3 from Maxim Integrated is a 5-pin SOT23 programmable supervisory IC that monitors VCC (factory-set at 3.08V ±2.5%), an adjustable undervoltage input (RST IN), and a manual-reset input (MR) to assert an active-low push/pull RESET signal. It guarantees valid reset assertion down to VCC = 1V, features 140ms minimum reset timeout, consumes only 8µA supply current, and rejects fast transients-making it ideal for multivoltage embedded control systems requiring reliable power-on and brownout protection.

For engineers reviewing the MAX6309UK31D3 datasheet, MAX6309UK31D3 pinout, MAX6309UK31D3 application, or MAX6309UK31D3 equivalent, key selection considerations include its factory-trimmed 3.08V VCC threshold, 140ms timeout, MR input with internal 63.5kΩ pull-up, push/pull RESET output capable of sourcing/sinking at VCC ≥2.5V, and immunity to sub-µs VCC transients per typical operating characteristics.

Technical Context

The MAX6309UK31D3 implements a dual-monitoring architecture: a factory-trimmed internal voltage divider sets the primary VCC reset threshold at 3.08V, while a separate comparator monitors the RST IN pin against a precise 1.23V reference (±0.03V). Its push/pull RESET output drives high/low without external pull-up, enabling direct interface with µP reset inputs requiring active-high or active-low logic levels depending on system design.

Reset assertion occurs when either VCC falls below 3.08V (±2.5% over temperature), RST IN drops below 1.23V, or MR is pulled low. The internal timer enforces a guaranteed minimum 140ms reset pulse width after all monitored conditions return to valid states, and the device remains functional across -40°C to +85°C with guaranteed operation down to VCC = 1V.

Key Specifications

Pinout & Package

MAX6309UK31D3 is housed in a 5-pin SOT23 package (outline U5+1, land pattern 90-0174), optimized for space-constrained PCB layouts and reflow-compatible assembly. Pin 1 is RESET, Pin 2 is GND, Pin 3 is RST IN, Pin 4 is MR, and Pin 5 is VCC - verified from Maxim's official pin configuration diagram for MAX6306/MAX6309/MAX6312 variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6312UK31D3, the MAX6309UK31D3 omits overvoltage detection to reduce complexity and cost while retaining identical VCC supervision and manual reset capability; versus TPS3808G33DBVR, it provides greater flexibility with dual-input monitoring and push/pull output but at higher quiescent current.

Availability

MAX6309UK31D3 is available at Aetrix Electronics and suitable for industrial PLCs, medical diagnostics equipment, automotive body controllers, smart energy meters, and battery-powered instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6309UK31D3 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, medical, and automotive applications - emphasizing reliability, low power, and integration.

The MAX6305–MAX6313 family was engineered specifically for multivoltage microprocessor supervision in space- and power-constrained systems, delivering factory-programmable thresholds, multiple input monitoring, and robust transient immunity in miniature SOT23 packages.

FAQ

What is the exact factory-programmed VCC reset threshold for MAX6309UK31D3?

The MAX6309UK31D3 has a factory-trimmed VCC reset threshold of 3.08V, with ±2.5% tolerance over the full -40°C to +85°C operating temperature range. This value is confirmed in Table 1 of the datasheet under "31" index (3.034V min / 3.080V typ / 3.126V max at +25°C), and applies specifically to the MAX6309UK31D3 variant - not inferred from adjacent part numbers. The threshold is set by an internal precision voltage divider and requires no external calibration.

Does MAX6309UK31D3 support monitoring of a second voltage rail besides VCC?

Yes, MAX6309UK31D3 supports secondary rail monitoring via its RST IN pin, which compares an externally applied voltage (using a resistor divider) against a precise 1.23V internal reference. This enables supervision of rails such as 1.8V or 2.5V alongside the primary 3.3V VCC supply. The RST IN input features ±25nA leakage and built-in hysteresis, allowing megohm-level divider resistors and noise immunity - a capability explicitly documented for MAX6309 in the Pin Description and Adjustable Reset Inputs sections.

What is the function and electrical behavior of the MR pin on MAX6309UK31D3?

The MR (Manual Reset) pin on MAX6309UK31D3 is an active-low input with an internal 63.5kΩ pull-up resistor. Pulling MR low forces immediate reset assertion, which persists for the full 140ms timeout period after MR returns high. The pin accepts TTL logic in 5V systems and CMOS levels in 3V systems, and its ESD protection requires MR's driving supply to match VCC to prevent forward-biasing. This behavior is specified in the Electrical Characteristics table under "MR Input" parameters and confirmed in the Detailed Description section.

Is the RESET output of MAX6309UK31D3 open-drain or push/pull?

The RESET output of MAX6309UK31D3 is active-low push/pull, meaning it actively drives both high and low states without requiring an external pull-up resistor. This is confirmed in the Pin Description table ("Active-Low, Push/Pull Reset Output for the MAX6308/MAX6309/MAX6310") and Electrical Characteristics (VOH/VOL specs showing sourcing/sinking capability at defined VCC and current conditions). Unlike open-drain variants (e.g., MAX6305), MAX6309UK31D3's output structure simplifies interface with µP reset pins requiring driven logic levels.

What is the minimum VCC voltage at which MAX6309UK31D3 guarantees valid RESET assertion?

MAX6309UK31D3 guarantees valid RESET assertion down to VCC = 1V, as explicitly stated in the Features list ("Guaranteed RESET Valid to VCC = 1V") and Electrical Characteristics table (VOL/VOH test conditions including VCC > 1.0V). Below 1V, output drive strength degrades significantly; however, for all normal operation within its specified VCC range (≥3.16V, per "VCC = (VTH + 2.5%) to +5.5V"), the device maintains full reset functionality with guaranteed timing and voltage levels.