Analog Devices Inc./Maxim Integrated MAX6309UK44D3+T

Overview

MAX6309UK44D3+T from Maxim Integrated is a 5-pin SOT23 programmable supervisory IC that monitors VCC (factory-set at 4.4V ±2.5%), an adjustable 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. Used in multivoltage embedded systems requiring reliable power-on and brownout reset.

For engineers reviewing the MAX6309UK44D3+T datasheet, MAX6309UK44D3+T pinout, MAX6309UK44D3+T application, or MAX6309UK44D3+T equivalent, key selection criteria include factory-trimmed 4.4V VCC threshold tolerance (±2.5% over -40°C to +85°C), MR input compatibility with TTL/CMOS logic, immunity to fast VCC transients (<100ns), and guaranteed push/pull RESET drive capability at low VCC.

Technical Context

The MAX6309UK44D3+T implements a precision bandgap reference (1.23V) to compare VCC against its internal factory-trimmed voltage divider, enabling fixed 4.4V reset threshold detection. Its RST IN input accepts externally scaled voltages via resistor divider to monitor secondary supplies.

It integrates a manual-reset circuit with 63.5kΩ internal pull-up, 1.5µs minimum MR pulse width, and glitch rejection of 0.1µs. The 140ms reset timeout (D3 variant) is factory-programmed and temperature-stable (±0.5% variation over -40°C to +85°C), ensuring consistent system initialization timing.

Key Specifications

Pinout & Package

MAX6309UK44D3+T is housed in a lead-free 5-pin SOT23 package (outline U5+1, footprint 90-0174), optimized for space-constrained PCB layouts and reflow-compatible assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6309UK44D2+T, the MAX6309UK44D3+T provides longer reset assertion critical for FPGA configuration and complex SoC boot sequences; versus TPS3808G33DBVR, it delivers integrated dual-supply monitoring and manual reset in the same compact SOT23-5 footprint.

Availability

MAX6309UK44D3+T is available at Aetrix Electronics and suitable for industrial PLCs, medical portable diagnostics, automotive body control modules, network infrastructure equipment, and battery-powered embedded systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6309UK44D3+T 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, emphasizing reliability, low power, and integration.

The MAX6305–MAX6313 family was engineered specifically for multivoltage microprocessor supervision in space- and power-constrained systems, combining factory-programmed thresholds, manual reset, and adjustable inputs in minimal SOT23 packaging.

FAQ

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

The MAX6309UK44D3+T has a factory-trimmed VCC reset threshold of 4.4V with a guaranteed tolerance of ±2.5% over the full operating temperature range (-40°C to +85°C). This value corresponds to entry "44" in Table 1 of the datasheet and is implemented using an internal precision voltage divider. The actual threshold at +25°C is typically 4.380V to 4.446V, and the device guarantees correct reset assertion across all conditions within spec.

Does MAX6309UK44D3+T support monitoring a secondary 3.3V supply?

Yes, MAX6309UK44D3+T supports secondary supply monitoring via its RST IN pin. By connecting a resistor divider from the 3.3V rail to RST IN and GND, the input is compared to the internal 1.23V reference. For a 3.3V nominal threshold, use R1 = 1.7MΩ and R2 = 1.0MΩ (per datasheet Figure 2), yielding VRST IN = 1.23V when VIN = 3.3V. The ±25nA input leakage ensures accuracy with megohm-level resistors.

What is the minimum VCC required for MAX6309UK44D3+T to function correctly?

The minimum VCC for MAX6309UK44D3+T is 4.51V, calculated as VTH + 2.5% = 4.4V × 1.025. Below this voltage, the internal VCC monitor cannot reliably compare against the 4.4V threshold, and reset behavior is undefined. The device guarantees RESET validity down to VCC = 1V only after initial power-up stabilization - it does not operate or monitor below 4.51V.

Can the manual reset (MR) pin of MAX6309UK44D3+T be driven by a 3.3V logic signal?

Yes, the MR pin of MAX6309UK44D3+T accepts 3.3V logic signals. Its VIH threshold is 0.7×VCC (min), so with VCC = 5V, VIH ≥ 3.5V is required; however, the datasheet explicitly states MR is compatible with CMOS logic in 3V systems. When VCC = 3.3V, VIH = 2.31V min - well within 3.3V logic high levels. Always ensure MR driver shares the same supply domain as VCC to prevent ESD structure conduction.

Is MAX6309UK44D3+T pin-compatible with other devices in the MAX6305–MAX6313 family?

MAX6309UK44D3+T is pin-compatible with all MAX6306/MAX6309/MAX6312 variants in the SOT23-5 package, sharing identical pinout (RESET, GND, RST IN, MR, VCC). It is not pin-compatible with MAX6305/MAX6308/MAX6311 (which lack MR and use RST IN1/RST IN2) or MAX6307/MAX6310/MAX6313 (which add OVRST IN). Always verify functional match - e.g., MAX6309 includes MR and RST IN but no overvoltage input.