Analog Devices Inc./Maxim Integrated MAX6309UK42D3

Overview

MAX6309UK42D3 from Maxim Integrated is a 5-pin SOT23 programmable supervisory IC that monitors VCC (factory-set to 4.20V ±2.5%), an external 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 = 1.0V, features 140ms minimum reset timeout, and draws only 8µA supply current - ideal for multivoltage embedded systems requiring reliable power-up/brownout protection.

For engineers reviewing the MAX6309UK42D3 datasheet, MAX6309UK42D3 pinout, MAX6309UK42D3 application, or MAX6309UK42D3 equivalent, this page delivers verified circuit role (dual-supply voltage supervisor with MR), precise factory-trimmed threshold (4.20V), guaranteed reset timeout (140ms min), low-quiescent-current operation (8µA), and SOT23-5 package compatibility - all critical for portable, industrial, and battery-powered designs.

Technical Context

The MAX6309UK42D3 integrates a factory-trimmed voltage divider to monitor VCC against a 4.20V nominal threshold with ±2.5% tolerance over –40°C to +85°C, plus a dedicated RST IN comparator referenced to 1.23V internal bandgap. Its push/pull RESET output sources/sinks current (VOH = 0.8×VCC, VOL = 0.3V at ISINK = 1.2mA), eliminating external pull-up components.

It implements a deterministic reset sequence: RESET remains asserted while any monitored supply (VCC or RST IN) falls below its threshold, and holds active for ≥140ms after all supplies recover. The MR input includes a 63.5kΩ internal pull-up and guarantees reset assertion for ≥500ns after MR deassertion, supporting noise-immune manual reset via momentary switch.

Key Specifications

Pinout & Package

MAX6309UK42D3 is housed in a 5-pin SOT23 package (outline U5+1, land pattern 90-0174), optimized for space-constrained PCB layouts and compatible with standard reflow processes. Pin 1 is RESET, Pin 2 is GND, Pin 3 is RST IN, Pin 4 is MR, and Pin 5 is VCC - matching JEDEC MO-178AB mechanical dimensions and thermal profile.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6312UK42D3, MAX6309UK42D3 omits overvoltage detection to reduce complexity and cost where only undervoltage supervision is needed; versus TPS3808G33DBVR, it offers programmable threshold, dual-input monitoring, and manual reset - enabling tighter system-level power integrity control.

Availability

MAX6309UK42D3 is available at Aetrix Electronics and suitable for industrial PLCs, portable medical devices, automotive body controllers, and point-of-sale terminals requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6309UK42D3 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 high-performance analog and mixed-signal ICs for power, sensing, and interface applications, with emphasis on reliability and integration for demanding environments.

The MAX6305–MAX6313 family was engineered specifically for multivoltage microprocessor supervision in space- and power-constrained systems, combining factory-trimmed accuracy, ultra-low quiescent current, and integrated reset timing in minimal SOT23-5 footprint.

FAQ

What is the exact factory-programmed VCC reset threshold for MAX6309UK42D3?

The MAX6309UK42D3 has a factory-trimmed VCC reset threshold of 4.20V 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 "42" suffix in the part number. The threshold is implemented via an internal precision voltage divider and does not require external calibration. MAX6309UK42D3 maintains this specification under all specified load and supply conditions.

Does MAX6309UK42D3 support manual reset functionality, and how is it implemented?

Yes, MAX6309UK42D3 includes a dedicated MR (manual reset) input on Pin 4. It features an internal 63.5kΩ pull-up resistor, allowing direct connection of a momentary switch to ground with no external components. A logic-low pulse ≥1.5µs on MR forces RESET assertion for the full timeout period (≥140ms) after MR returns high. MAX6309UK42D3 guarantees MR-to-reset delay of ≤500ns and rejects glitches <0.1µs, making it robust in noisy environments.

What is the minimum VCC voltage at which MAX6309UK42D3 guarantees valid RESET output?

MAX6309UK42D3 guarantees valid RESET output down to VCC = 1.0V, as specified in the Electrical Characteristics table. Below this voltage, the push/pull driver's sourcing/sinking capability degrades, but within the 1.0V–5.5V operating range, RESET maintains VOH ≥ 0.8×VCC and VOL ≤ 0.3V (at ISINK = 1.2mA). This ensures reliable microcontroller reset assertion even during deep brownout conditions. MAX6309UK42D3 meets this spec across –40°C to +85°C.

Can MAX6309UK42D3 monitor a second voltage rail besides VCC?

Yes, MAX6309UK42D3 includes a dedicated RST IN input (Pin 3) that compares an external voltage to a 1.23V internal reference. By connecting a resistor divider from the secondary rail to RST IN, designers can program undervoltage detection for any rail - such as 3.3V, 2.5V, or 1.8V - independent of the 4.20V VCC threshold. MAX6309UK42D3 supports this function with ±0.06V reference tolerance and ±25nA input leakage, enabling megohm-level divider resistors without significant error.

What package type and RoHS status does MAX6309UK42D3 use?

MAX6309UK42D3 is supplied in a 5-pin SOT23 package (JEDEC MO-178AB, Maxim outline U5+1) with lead-free termination. The standard ordering suffix "-T" denotes lead-free packaging compliant with RoHS Directive 2011/65/EU. Footprint land pattern 90-0174 is recommended, and the device supports standard reflow soldering profiles including peak temperatures up to +260°C. MAX6309UK42D3 is available only in tape-and-reel format.