Analog Devices Inc./Maxim Integrated MAX6309UK44D3

Overview

MAX6309UK44D3 from Maxim Integrated is a 5-pin SOT23 programmable supervisory IC that monitors VCC (factory-set to 4.4V ±2.5%), an external undervoltage input (RST IN), and a manual reset (MR) input, asserting an active-low push/pull RESET output for microprocessor system initialization. It features 140ms minimum reset timeout, 8µA supply current, and guaranteed RESET validity down to VCC = 1V. It is used in multivoltage embedded systems requiring reliable power-on and brownout reset.

For engineers reviewing the MAX6309UK44D3 datasheet, MAX6309UK44D3 pinout, MAX6309UK44D3 application, or MAX6309UK44D3 equivalent, key selection criteria include factory-trimmed 4.4V VCC threshold tolerance, MR input compatibility with TTL/CMOS logic, immunity to sub-1µs VCC transients, and operation across -40°C to +85°C industrial temperature range.

Technical Context

The MAX6309UK44D3 implements a precision bandgap reference (1.23V ±0.03V) feeding three independent comparators: one for internal VCC monitoring via factory-trimmed resistor divider, one for external RST IN undervoltage detection, and one for MR assertion. Its reset generator includes a temperature-stable RC timer delivering 140ms (min) timeout with ±10% variation over temperature.

It uses a push/pull output stage capable of sourcing 800µA at VCC > 4.25V and sinking 3.2mA - eliminating external pull-up resistors. The MR input integrates a 63.5kΩ internal pull-up and rejects <0.1µs glitches, enabling direct switch connection without debounce circuitry.

Key Specifications

Pinout & Package

MAX6309UK44D3 is housed in a 5-pin SOT23 package (U5+1 outline, 2.0mm × 1.25mm footprint), optimized for space-constrained PCB layouts in portable and multilayer designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar programmable reset IC applications.

Compared with MAX6309UK44D3, MAX6312UK29D3 offers identical architecture but targets lower-voltage rails, while TPS3808G33DBVR trades multi-input flexibility and push/pull drive for lower current and tighter fixed-threshold accuracy - making MAX6309UK44D3 optimal for 5V/3.3V multirail systems needing manual reset and external monitoring.

Availability

MAX6309UK44D3 is available at Aetrix Electronics and suitable for industrial PLCs, medical infusion pumps, automotive body controllers, and point-of-sale terminals requiring stable component supply across extended temperature ranges and long production lifecycles.

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 industrial, communications, and computing applications, emphasizing reliability, integration, and low-power operation.

MAX6309UK44D3 belongs to the MAX6305–MAX6313 family of programmable supervisory circuits engineered for multivoltage embedded systems requiring simultaneous monitoring of primary and auxiliary rails with manual reset capability.

FAQ

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

The MAX6309UK44D3 has a factory-trimmed VCC reset threshold of 4.4V with ±2.5% tolerance over the full -40°C to +85°C operating range. This value is laser-trimmed during manufacturing and corresponds to the "44" in the part number per Table 1 of the datasheet. The threshold is implemented using an internal resistor divider referenced to a 1.23V bandgap, ensuring stability without external components.

Does MAX6309UK44D3 require an external pull-up resistor on the RESET pin?

No, MAX6309UK44D3 does not require an external pull-up resistor because it features an active-low push/pull RESET output. The output can both sink up to 3.2mA and source up to 800µA, allowing direct connection to microprocessor reset inputs without additional components. This design eliminates BOM cost and board space associated with discrete pull-ups while improving noise immunity.

Can MAX6309UK44D3 monitor a 3.3V supply in addition to its 4.4V VCC rail?

Yes, MAX6309UK44D3 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 GND, the device compares the divided voltage against its internal 1.23V reference. When the 3.3V rail drops below the programmed threshold (e.g., 2.97V), RST IN asserts reset independently of the 4.4V VCC condition - enabling true dual-rail supervision in multivoltage systems.

What is the minimum pulse width required on the MR pin to trigger reset in MAX6309UK44D3?

The MR pin of MAX6309UK44D3 requires a minimum low pulse width of 1.5µs at -40°C to +85°C to reliably initiate a reset. At 0°C to +70°C, the minimum is 1µs. The device incorporates 0.1µs glitch rejection, meaning shorter noise spikes are ignored. This specification ensures robust manual reset functionality even in electrically noisy environments without external debouncing circuitry.

Is MAX6309UK44D3 compatible with both 3V and 5V logic systems for the MR input?

Yes, MAX6309UK44D3 MR input is compatible with both 3V and 5V logic systems. Its VIH threshold scales with VCC (0.7×VCC min when VTH < 4.0V) and VIL is fixed at 0.8V max, meeting TTL and CMOS logic level requirements across operating voltages. This allows direct interfacing with 3.3V microcontrollers or 5V legacy logic without level-shifting circuitry - simplifying design in mixed-voltage boards.