Analog Devices Inc./Maxim Integrated MAX6425UK26

Overview

MAX6425UK26 from Maxim Integrated is a low-power microprocessor supervisor IC with open-drain active-low reset output, 2.625V factory-trimmed reset threshold (±2.5% over -40°C to +125°C), capacitor-adjustable reset timeout (275µs minimum), and guaranteed operation down to VCC = 1V. It monitors system supply voltage in portable, battery-powered, and automotive electronics to prevent code-execution errors during power-up, brownout, or power-down.

For engineers reviewing the MAX6425UK26 datasheet, MAX6425UK26 pinout, MAX6425UK26 application, or MAX6425UK26 equivalent, key selection criteria include its SOT23-5 open-drain RESET output, 1.6µA typical quiescent current, immunity to short VCC transients (<50µs at 100mV overdrive), and compatibility with multi-rail logic interfacing via external pullup.

Technical Context

The MAX6425UK26 uses an internal 240nA current source to charge an external capacitor (CSRT) connected between SRT and GND, generating a ramp voltage compared to a 0.65V internal reference to set the reset timeout period. Reset assertion occurs when VCC falls below 2.625V, and deassertion is delayed until the CSRT voltage reaches 0.65V after VCC recovers.

Its open-drain RESET output supports wired-OR configurations and logic-level translation across supplies from 0V to 5.5V using an external pullup resistor (10kΩ–100kΩ). The device guarantees valid RESET output down to VCC = 1V but requires external pulldown for validity at VCC = 0V - a constraint not applicable to push-pull variants.

Key Specifications

Pinout & Package

MAX6425UK26 is housed in a 5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), RoHS-compliant and available in leaded or lead-free variants. Pin 3 is internally unconnected (N.C.) and may be tied to GND per layout best practice.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6425UK26, NCP302LSN26T1G offers lower IQ but sacrifices timeout adjustability and open-drain versatility, while TLV803EB26DBZR reduces size and IQ at the cost of tunability and guaranteed VCC = 1V reset validity - making MAX6425UK26 the optimal choice for designs needing field-configurable reset timing and robust multi-supply interfacing.

Availability

MAX6425UK26 is available at Aetrix Electronics and suitable for battery-powered medical sensors, automotive body control modules, and industrial IoT edge nodes requiring stable component supply across extended temperature ranges (-40°C to +125°C) and long product lifecycles.

Supply support for MAX6425UK26 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and computing applications.

The MAX6421–MAX6426 family was designed specifically for ultra-low-power, precision voltage monitoring in space-constrained, battery-sensitive systems where reset accuracy, glitch immunity, and flexible timeout configuration are critical.

FAQ

What is the exact reset threshold voltage of MAX6425UK26 and how tightly is it specified?

The MAX6425UK26 features a factory-laser-trimmed reset threshold of 2.625V, with guaranteed accuracy of ±2.5% over the full operating temperature range (-40°C to +125°C). This tolerance is confirmed in the Electrical Characteristics table under "VCC Reset Threshold Accuracy" and applies directly to the '26' suffix variant, not derived from interpolation or family averages.

Can MAX6425UK26 generate a valid reset signal when VCC drops below 1.0V?

No - the MAX6425UK26 guarantees valid RESET output only down to VCC = 1.0V. Below this voltage, output drive capability collapses, and the open-drain RESET line may float unpredictably. For applications requiring asserted reset down to VCC = 0V, a 100kΩ pulldown resistor from RESET to GND is required, as explicitly documented in the Applications Information section.

How do I calculate the external capacitor value needed for a specific reset timeout period with MAX6425UK26?

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 5ms timeout requires CSRT = (0.005 − 0.000275) / 2.73×10⁶ ≈ 1730pF. Ceramic capacitors with <10nA leakage are mandatory; avoid electrolytics or high-leakage dielectrics.

Is the N.C. pin (Pin 3) on MAX6425UK26 safe to leave floating on the PCB?

No - although Pin 3 is Not Connected internally, Maxim's Layout Consideration section explicitly recommends tying it to GND. This minimizes stray capacitance and leakage currents near the sensitive SRT pin (Pin 1), which could otherwise introduce timing errors in the capacitor-adjusted reset timeout period.

Does MAX6425UK26 support wired-OR reset configurations with other open-drain reset sources?

Yes - the open-drain RESET output of MAX6425UK26 is expressly designed for wired-OR operation. As shown in Figure 2 of the datasheet, an external open-drain logic signal (e.g., from a watchdog timer or manual reset switch) can be directly connected to the same RESET net, allowing multiple sources to hold the microcontroller in reset simultaneously.