Analog Devices Inc./Maxim Integrated MAX6309UK46D3

Overview

MAX6309UK46D3 from Maxim Integrated is a 5-pin SOT23 programmable supervisory circuit that monitors VCC and an external undervoltage input (RST IN), asserts active-low push/pull RESET when either falls below its threshold, and features factory-set 4.63V VCC reset threshold with ±2.5% tolerance over -40°C to +85°C and 140ms minimum reset timeout. It draws only 8µA supply current and guarantees valid RESET output down to VCC = 1V, making it suitable for portable 3.3V/5V multivoltage systems requiring reliable brownout protection.

For engineers reviewing the MAX6309UK46D3 datasheet, MAX6309UK46D3 pinout, MAX6309UK46D3 application, or MAX6309UK46D3 equivalent, key selection considerations include its dual-supply monitoring capability (VCC + RST IN), manual-reset input with internal 63.5kΩ pull-up, immunity to fast VCC transients, guaranteed operation at VCC ≥ 1V, and compatibility with microprocessor reset initialization in embedded controllers and battery-powered instrumentation.

Technical Context

The MAX6309UK46D3 implements a precision bandgap reference (1.23V) to compare VCC against a factory-trimmed internal voltage divider set to 4.63V nominal, while simultaneously monitoring an external RST IN signal referenced to the same 1.23V threshold. Its reset generator includes a temperature-stable RC timer delivering a guaranteed minimum 140ms timeout after all monitored supplies return to regulation.

This device integrates a manual-reset input (MR) with TTL/CMOS-compatible logic thresholds, internal ESD protection, and glitch rejection of ≤0.1µs. The push/pull RESET output sources up to 800µA at VCC > 4.25V and sinks 3.2mA, eliminating external pull-up resistors in most µP interface configurations.

Key Specifications

Pinout & Package

MAX6309UK46D3 is housed in a 5-pin SOT23 package (outline U5+1, land pattern 90-0174), measuring 2.9mm × 1.6mm × 1.1mm, RoHS-compliant and available in leaded (-T) or lead-free (+T) variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6312UK46D3, MAX6309UK46D3 omits overvoltage detection to reduce cost and simplify design for undervoltage-only use cases; versus TPS3808G33DBVR, it provides flexible dual-rail monitoring and manual reset at higher quiescent current but broader voltage range and application coverage.

Availability

MAX6309UK46D3 is available at Aetrix Electronics and suitable for portable computers, industrial controllers, intelligent instruments, and battery-powered medical devices requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6309UK46D3 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 computing applications, emphasizing reliability, low power, and integration.

The MAX6305–MAX6313 family was engineered specifically for multivoltage microprocessor system supervision, combining factory-programmed thresholds, dual-input monitoring, and transient-immune reset generation in minimal SOT23 packaging.

FAQ

What is the exact factory-set VCC reset threshold for MAX6309UK46D3?

The MAX6309UK46D3 has a nominal VCC reset threshold of 4.63V, with ±2.5% tolerance over the full -40°C to +85°C operating temperature range. This value is factory-trimmed using an internal resistor divider and corresponds to the "46" suffix per Table 1 in the datasheet. The actual measured threshold at +25°C falls between 4.514V and 4.746V.

Does MAX6309UK46D3 support monitoring of a secondary voltage rail?

Yes, MAX6309UK46D3 supports secondary rail monitoring via its RST IN pin, which compares an external voltage to a precise 1.23V internal reference. By connecting a resistor divider from the secondary rail to RST IN and GND, designers can configure undervoltage detection for any voltage above ~1.25V - for example, setting a 2.5V threshold for a 3.3V auxiliary supply.

What is the function of the MR pin on MAX6309UK46D3?

The MR (manual-reset) pin on MAX6309UK46D3 is an active-low input that forces the RESET output low when pulled below its VIH threshold (~0.7×VCC for VTH < 4.0V). It features an internal 63.5kΩ pull-up resistor, allowing direct connection of a momentary switch to GND. RESET remains asserted for the full 140ms timeout period after MR returns high, ensuring clean µP initialization.

Can MAX6309UK46D3 operate reliably during severe supply brownouts?

Yes, MAX6309UK46D3 guarantees valid RESET output down to VCC = 1V, meaning it continues asserting reset even as the main supply collapses. Its push/pull output maintains specified sink/source capability (3.2mA/800µA) across the 2.5V–5.5V operating range, and the internal reset timer remains functional throughout this range - critical for preventing partial execution during deep brownouts.

Is MAX6309UK46D3 pin-compatible with other devices in the MAX6305–MAX6313 family?

MAX6309UK46D3 shares the identical SOT23-5 pinout with MAX6306, MAX6307, MAX6310, MAX6312, and MAX6313 variants, including RESET, GND, RST IN, MR, and VCC assignments. However, functional differences exist: MAX6305/MAX6308/MAX6311 lack MR and use open-drain or active-high outputs, so electrical compatibility requires verification of reset polarity, drive strength, and input configuration before substitution.