Analog Devices Inc./Maxim Integrated MAX6422US44

Overview

MAX6422US44 from Maxim Integrated is a low-power, active-high push-pull microprocessor reset supervisor IC in SOT143-4 package, monitoring VCC from 1.6V to 5V with factory-trimmed 4.375V reset threshold (±2.5% over -40°C to +125°C), 1.6µA typical quiescent current, and capacitor-adjustable reset timeout (275µs base + 2.73×10⁶ × CSRT). It ensures reliable µP reset assertion during brownout and power-up in battery-powered controllers.

For engineers reviewing the MAX6422US44 datasheet, MAX6422US44 pinout, MAX6422US44 application, or MAX6422US44 equivalent, key selection criteria include its active-high push-pull output, guaranteed reset validity down to VCC = 1V, immunity to sub-50µs VCC transients at 100mV overdrive, and compatibility with 4-pin SOT143 layout constraints.

Technical Context

The MAX6422US44 implements a precision voltage comparator with laser-trimmed reference and hysteresis (4×VTH), coupled to a 240nA current source charging an external capacitor on the SRT pin to generate the reset timeout delay. Its internal ramp circuit compares the SRT voltage against a fixed 0.65V threshold to control reset deassertion timing.

Unlike open-drain variants, the MAX6422US44 uses a push-pull output stage capable of sourcing up to 800µA at VCC ≥ 4.5V (VOH ≥ 0.8×VCC) and sinking up to 3.2mA (VOL ≤ 0.4V), eliminating need for external pullup resistors. It operates across full industrial temperature range (-40°C to +125°C) with supply voltage range 1.0V to 5.5V.

Key Specifications

Pinout & Package

MAX6422US44 is housed in a 4-pin SOT143-4 surface-mount package (outline 21-0052), with 1.3mm × 1.3mm footprint and 0.95mm height. Pin 1 is VCC, Pin 2 is GND, Pin 3 is RESET (active-high push-pull), and Pin 4 is SRT (capacitor-adjustable timeout input).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor reset supervision applications.

Compared with MAX6422US44, MAX6422XS44-T offers identical functionality in a smaller package but reduced thermal margin, while TPS3808G33DBVR trades adjustability and threshold precision for lower cost and simpler implementation in 3.3V-only systems.

Availability

MAX6422US44 is available at Aetrix Electronics and suitable for battery-powered controllers, medical monitoring devices, and automotive body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6422US44 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 power, sensing, and interface applications, with focus on reliability and low-power operation.

The MAX6421–MAX6426 family targets ultra-low-power microprocessor supervision in portable, medical, and automotive systems, emphasizing capacitor-adjustable timing, wide VCC range, and guaranteed operation down to 1V.

FAQ

What is the factory-trimmed reset threshold voltage for MAX6422US44?

The MAX6422US44 has a factory-trimmed reset threshold of 4.375V, with ±2.5% accuracy over the full -40°C to +125°C operating temperature range. This value is defined by the '44' suffix per Table 1 in the datasheet and is laser-trimmed during production to eliminate external resistor networks. The MAX6422US44 maintains this precision without requiring calibration in end equipment.

How do I calculate the external capacitor value for a specific reset timeout period with MAX6422US44?

Use the formula CSRT = (tRP − 275µs) / 2.73×10⁶, where tRP is the desired timeout in seconds and CSRT is in farads. For example, a 100ms timeout requires CSRT = (0.1 − 0.000275) / 2.73×10⁶ ≈ 36.5nF. The MAX6422US44 datasheet specifies ceramic capacitors with leakage <10nA for optimal accuracy, and the SRT pin must be routed with minimal trace length to avoid stray capacitance affecting timing.

Does MAX6422US44 support operation down to 1.0V VCC, and what happens to the RESET output below that?

Yes, the MAX6422US44 guarantees valid RESET output behavior down to VCC = 1.0V, including proper logic levels and timing. Below 1.0V, the internal circuitry cannot maintain specified VOH/VOL performance, so RESET may become indeterminate. For applications requiring asserted reset down to 0V, a 100kΩ pullup resistor from RESET to VCC is recommended - a design detail explicitly validated for the MAX6422US44 in the datasheet's Figure 4.

What is the maximum transient duration that MAX6422US44 can ignore when VCC dips 100mV below its 4.375V threshold?

The MAX6422US44 is immune to VCC transients ≤50µs in duration when the dip magnitude is ≥100mV below the 4.375V threshold, as shown in the "Maximum Transient Duration vs. Reset Threshold Overdrive" graph (toc05). This immunity prevents false resets during switching noise or load-dump events. The MAX6422US44 achieves this via internal filtering and hysteresis, not external components.

Can MAX6422US44 be used with a 1.8V microcontroller supply rail?

Yes, the MAX6422US44 supports VCC from 1.0V to 5.5V and monitors its own supply as the reset threshold reference. When powered from a 1.8V rail, it will assert reset if VCC falls below 4.375V - which is impossible. Therefore, MAX6422US44 is intended for supervision of higher-voltage rails (e.g., 4.5V or 5V) that power the µP's core or I/O. For 1.8V rail supervision, a different suffix (e.g., '18' = 1.800V) would be required - the MAX6422US44 itself is not suitable for 1.8V monitoring.