Analog Devices Inc./Maxim Integrated MAX6425UK22

Overview

MAX6425UK22 from Maxim Integrated is a low-power microprocessor supervisor IC with open-drain active-low reset output, 2.188V ±2.5% factory-trimmed reset threshold, capacitor-adjustable reset timeout (275µs base + 2.73s/F × CSRT), and guaranteed operation down to VCC = 1V. It monitors system supply voltage in portable, battery-powered, and automotive electronics to prevent erroneous µP execution during brownout or power-up.

For engineers reviewing the MAX6425UK22 datasheet, MAX6425UK22 pinout, MAX6425UK22 application, or MAX6425UK22 equivalent, key selection criteria include its SOT23-5 open-drain reset architecture, 1.6µA typical quiescent current, 240nA SRT ramp current, immunity to sub-50µs VCC transients at 100mV overdrive, and compatibility with multi-rail logic interfacing via external pullup.

Technical Context

The MAX6425UK22 implements a precision voltage monitor with laser-trimmed resistive divider setting the 2.188V reset threshold, coupled to an internal 240nA current source charging an external capacitor on the SRT pin. Reset assertion occurs when VCC falls below threshold; deassertion requires both VCC rise above threshold and SRT capacitor voltage ramping to 0.65V.

Its open-drain RESET output supports wired-OR configurations and logic-level translation across supplies up to 5.5V using an external pullup (10kΩ–100kΩ). The device guarantees valid reset signaling for VCC ≥ 1V but requires external pulldown for validity near 0V - unlike push-pull variants.

Key Specifications

Pinout & Package

MAX6425UK22 is housed in a 5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), RoHS-compliant, with thermal pad option. Pin 1 = SRT, Pin 2 = GND, Pin 3 = N.C., Pin 4 = VCC, Pin 5 = RESET.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP302HS22T1G and TLV809E22DBZR, MAX6425UK22 uniquely delivers capacitor-adjustable timeout and open-drain output in SOT23-5 - essential for designs requiring timing flexibility, wired-OR reset, or mixed-voltage µP compatibility.

Availability

MAX6425UK22 is available at Aetrix Electronics and suitable for battery-powered medical monitors, automotive body control modules, industrial handheld scanners, and smart energy meters requiring stable component supply across extended temperature ranges (–40°C to +125°C) and long-life reliability.

Supply support for MAX6425UK22 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 in industrial, automotive, and computing markets.

The MAX6425UK22 belongs to the MAX6340/MAX6421–MAX6426 family of low-power µP supervisors engineered for reliable reset generation in space-constrained, battery-sensitive systems where adjustable timing and multi-rail compatibility are critical.

FAQ

What is the exact reset threshold voltage of the MAX6425UK22 and how is it trimmed?

The MAX6425UK22 has a factory-laser-trimmed reset threshold of 2.188V, with ±2.5% accuracy over –40°C to +125°C. This value is set during wafer sort using precision laser trimming of on-chip resistors, ensuring tight tolerance without external components. The '22' suffix in MAX6425UK22 directly corresponds to the 2.188V nominal threshold per Table 1 in the datasheet, and the MAX6425UK22 maintains this specification across its full operating temperature range.

How do I calculate the external capacitor value for a desired reset timeout using the MAX6425UK22?

To set a specific reset timeout tRP (in seconds) with the MAX6425UK22, use the formula CSRT = (tRP − 275µs) / 2.73×10⁶, where CSRT is in farads. For example, a 100ms timeout requires CSRT = (0.1 − 0.000275) / 2,730,000 ≈ 36.5nF. Use low-leakage ceramic capacitors (≤10nA leakage) and keep SRT traces short and isolated from noise sources to maintain timing accuracy in the MAX6425UK22.

Why does the MAX6425UK22 use an open-drain RESET output instead of push-pull, and what pullup value should I use?

The MAX6425UK22 uses an open-drain RESET to enable wired-OR reset architectures and seamless interfacing with µPs operating at different supply voltages (e.g., 1.8V, 3.3V, or 5V). A 10kΩ–100kΩ pullup resistor to the target µP's VDD is recommended: 10kΩ ensures fast rise time and sufficient drive for heavy loads, while 100kΩ minimizes current draw. The MAX6425UK22 RESET can sink ≥50µA with VOL ≤0.3V, making either value robust across most applications.

Can the MAX6425UK22 operate reliably when the supply voltage drops below 1.0V, and what happens to RESET behavior?

The MAX6425UK22 is specified to guarantee valid RESET output only down to VCC = 1.0V. Below 1.0V, its internal circuitry loses regulation, and RESET may float or become indeterminate - especially problematic for µPs requiring clean reset assertion through full power collapse. To ensure RESET remains low near 0V, add a 100kΩ pulldown resistor from RESET to GND. This is a documented design requirement for the MAX6425UK22 in low-VCC scenarios, unlike push-pull variants which require pullups.

Is the MAX6425UK22 pin-compatible with other members of the MAX642x family, and which ones share the same SOT23-5 footprint?

Yes, the MAX6425UK22 is pin-compatible with MAX6340, MAX6424, and MAX6426 - all share the identical 5-pin SOT23-5 package and pinout (SRT, GND, N.C., VCC, RESET). However, output type differs: MAX6424 is push-pull, while MAX6340/MAX6425/MAX6426 are open-drain. Swapping MAX6425UK22 for MAX6424UK22 requires verifying µP reset input logic polarity and removing any existing pullup, as MAX6424 drives high actively.