Analog Devices Inc./Maxim Integrated MAX6425UK40

Overview

MAX6425UK40 from Maxim Integrated is a low-power microprocessor supervisor IC in SOT23-5 package, featuring an open-drain active-low RESET output, factory-trimmed 4.0V reset threshold (±2.5% over -40°C to +125°C), capacitor-adjustable reset timeout (275µs minimum), and guaranteed operation down to VCC = 1.0V. It monitors supply voltage in battery-powered embedded controllers and portable medical instruments.

For engineers reviewing the MAX6425UK40 datasheet, MAX6425UK40 pinout, MAX6425UK40 application, or MAX6425UK40 equivalent, key selection criteria include its open-drain logic compatibility with multiple supply rails, 1.6µA typical quiescent current, immunity to sub-50µs VCC transients at 100mV overdrive, and SRT pin's 240nA precision ramp current for accurate timeout setting.

Technical Context

The MAX6425UK40 implements a precision voltage-detection comparator with 4.0V laser-trimmed threshold and 4mV hysteresis, coupled to a capacitor-controlled timeout circuit using a 240nA internal current source charging the external SRT capacitor to a 0.65V reference. Reset assertion occurs when VCC falls below 4.0V; deassertion requires both VCC rise above threshold and SRT capacitor charge completion.

Its open-drain RESET output supports wired-OR configurations and logic-level translation across 0–5.5V pullup supplies, with VOL ≤ 0.3V at ISINK = 500µA (VCC ≥ 2.7V) and leakage <1.0µA when not asserted. The device operates over full industrial temperature range (-40°C to +125°C) with supply voltage range 1.0V to 5.5V.

Key Specifications

Pinout & Package

MAX6425UK40 is housed in a 5-pin SOT23-5 package (outline 21-0057), with 1.3mm × 2.9mm footprint and 0.95mm height. Pin 1 is VCC, Pin 2 is GND, Pin 3 is SRT (capacitor connection for timeout adjustment), Pin 4 is RESET (open-drain active-low output), and Pin 5 is NC (not internally connected, may be grounded).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6425UK40, NCP302HS40T1G offers lower quiescent current but eliminates timeout customization and requires push-pull interface changes, while TLV803E40DBZR reduces footprint and IQ but sacrifices the capacitor-based timing flexibility essential for diverse µP boot requirements.

Availability

MAX6425UK40 is available at Aetrix Electronics and suitable for battery-powered medical monitors, automotive body control modules, and industrial portable data loggers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6425UK40 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, automotive, and computing applications, emphasizing high reliability and low power.

The MAX6421–MAX6426 family delivers configurable microprocessor supervisors optimized for space-constrained, battery-sensitive systems requiring accurate voltage monitoring and programmable reset timing.

FAQ

What is the exact reset threshold voltage of MAX6425UK40 and how is it trimmed?

The MAX6425UK40 features a factory-laser-trimmed reset threshold of 4.000V with ±2.5% tolerance over -40°C to +125°C, confirmed in the Electrical Characteristics table under VTH parameter. This value corresponds to the '40' suffix in the part number per Table 1, and is achieved using on-chip laser trimming of precision resistors during final test, ensuring consistent performance without external calibration. The MAX6425UK40 maintains this accuracy across its full operating voltage range (1.0V to 5.5V) and temperature span.

How do I calculate the external capacitor value for a desired reset timeout period with MAX6425UK40?

To set a specific reset timeout period (tRP) for MAX6425UK40, use the formula CSRT = (tRP − 275µs) / 2.73×10⁶, where tRP is in seconds and CSRT is in farads. For example, a 100ms timeout requires CSRT = (0.1 − 0.000275) / 2.73×10⁶ ≈ 36.5nF. The MAX6425UK40's internal 240nA SRT current source charges this capacitor to 0.65V; ceramic capacitors with leakage <10nA are recommended. The MAX6425UK40 datasheet Figure 2 provides empirical validation of this relationship across CSRT values.

Can MAX6425UK40 drive a reset line referenced to a different supply voltage than VCC?

Yes, the MAX6425UK40's open-drain RESET output allows direct interfacing with reset lines referenced to voltages other than VCC, including 0V to 5.5V pullup supplies. This enables logic-level translation-e.g., using a 1.8V pullup for a low-voltage µP while VCC is 3.3V-without additional level-shifters. The MAX6425UK40 RESET pin sinks current only; the external pullup defines the high-state voltage. Designers must ensure the pullup resistor (typically 10kΩ–100kΩ) provides sufficient current for connected inputs while maintaining VOL ≤ 0.3V during assertion. This capability is explicitly validated in MAX6425UK40's Applications Information section.

What is the minimum VCC voltage at which MAX6425UK40 guarantees valid RESET output operation?

The MAX6425UK40 guarantees valid RESET output operation down to VCC = 1.0V, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Below this voltage, RESET current-sinking capability degrades significantly, potentially causing indeterminate logic states on CMOS inputs. The MAX6425UK40's design ensures that for VCC ≥ 1.0V, VOL remains ≤ 0.3V at ISINK = 500µA (VCC ≥ 2.7V) and ≤ 0.4V at ISINK = 3.2mA (VCC ≥ 4.5V), satisfying standard logic thresholds. This 1.0V lower limit enables reliable brownout detection in deeply discharged battery scenarios.

Is MAX6425UK40 pin-compatible with any industry-standard alternatives?

Yes, the MAX6425UK40 is explicitly documented as pin-compatible with NCP300–NCP303, MC33464/MC33465, S807/S808/S809, and RN5VD series supervisors per the "Ordering Information" section of the MAX6421–MAX6426 datasheet. This compatibility applies specifically to the 5-pin SOT23-5 package variants with open-drain outputs and matching pin 1 (VCC), pin 2 (GND), pin 3 (SRT/CAP), pin 4 (RESET), and pin 5 (NC) assignments. However, functional differences exist-including timeout adjustability, threshold accuracy, and quiescent current-so electrical validation is required despite mechanical pin alignment. The MAX6425UK40 retains full drop-in capability for footprint and basic connectivity.