Analog Devices Inc./Maxim Integrated MAX6424UK21

Overview

MAX6424UK21 from Maxim Integrated is a low-power microprocessor supervisor IC that monitors VCC supply voltage and asserts an active-low push-pull reset signal when voltage falls below 2.100V (±2.5% over temperature). It features capacitor-adjustable reset timeout (3.0–5.75ms with 1500pF), guaranteed reset validity down to VCC = 1V, and operates across –40°C to +125°C in 5-pin SOT23-5 packaging. It is used in battery-powered controllers and automotive ECUs for reliable power-on reset sequencing.

For engineers reviewing the MAX6424UK21 datasheet, MAX6424UK21 pinout, MAX6424UK21 application, or MAX6424UK21 equivalent, key selection considerations include its 2.1V reset threshold accuracy, 1.6µA typical quiescent current, push-pull output drive capability, SOT23-5 package compatibility with NCP300–NCP303 and MC33464/MC33465, and capacitor-based timeout flexibility for µP initialization timing control.

Technical Context

The MAX6424UK21 implements a precision voltage detector with laser-trimmed internal resistors to set its 2.100V nominal reset threshold, maintaining ±2.5% accuracy over –40°C to +125°C. Its reset assertion is triggered by VCC falling below VTH, with hysteresis of 4 × VTH (8.4mV) to prevent chatter during brownout recovery.

Reset deassertion timing is controlled by an internal 240nA current source charging an external capacitor (CSRT) connected between SRT and GND; the voltage ramp to 0.65V determines timeout duration. The push-pull RESET output drives low to ≤0.3V at 50µA and high to ≥0.8×VCC at 200µA, enabling direct interface with CMOS µP reset inputs without external pullups.

Key Specifications

Pinout & Package

MAX6424UK21 is housed in a 5-pin SOT23-5 package (package code U5+2, outline 21-0057), with exposed pad optional per Maxim's land pattern 90-0174. Pin 3 is internally unconnected (N.C.) and must be left floating or tied to GND per layout best practice.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP302LSN21T1G and MC33464D-21SEFR2, the MAX6424UK21 uniquely combines 2.1V precision, capacitor-adjustable sub-6ms timeout, and push-pull drive in a 5-pin SOT23 - making it optimal for space-constrained, timing-critical embedded systems requiring both low IQ and flexible reset timing.

Availability

MAX6424UK21 is available at Aetrix Electronics and suitable for automotive engine control units, battery-powered medical monitors, industrial PLC I/O modules, and set-top box power management systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6424UK21 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 computing applications, with emphasis on power efficiency, reliability, and integration.

The MAX6424UK21 belongs to Maxim's µP supervisor family engineered specifically for robust, low-power reset generation in battery-operated and high-temperature embedded systems - delivering accurate voltage monitoring with minimal footprint and design overhead.

FAQ

What is the exact reset threshold voltage of the MAX6424UK21 and how does it vary with temperature?

The MAX6424UK21 has a nominal reset threshold of 2.100V, with ±1.5% accuracy at +25°C and ±2.5% over the full –40°C to +125°C operating range. This tolerance is achieved via laser-trimmed internal resistors, and the device exhibits 4 × VTH (8.4mV) hysteresis to prevent oscillation near the trip point. The normalized threshold remains stable across temperature, as confirmed by the "Normalized Reset Threshold vs. Temperature" plot in the datasheet.

Can the MAX6424UK21 operate with a supply voltage lower than its reset threshold?

Yes, the MAX6424UK21 operates with VCC as low as 1.0V and guarantees valid RESET output down to VCC = 1.0V. Below 1.0V, its internal circuitry loses regulation, and RESET may become indeterminate. For applications requiring reset assertion all the way to 0V, a 100kΩ pulldown resistor on the RESET pin is recommended - but this is not needed for standard µP interfaces since most processors cease operation below 1.0V.

How do I calculate the external capacitor value for a desired reset timeout on the MAX6424UK21?

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 4.375ms timeout requires CSRT = (0.004375 − 0.000275) / 2.73 × 10⁶ = 1500pF. Ceramic capacitors with leakage <10nA are recommended; avoid electrolytics or high-leakage dielectrics that distort timing.

Is the MAX6424UK21 pin-compatible with other reset supervisors, and which ones?

Yes, the MAX6424UK21 is explicitly documented as pin-compatible with NCP300–NCP303, MC33464/MC33465, S807/S808/S809, and RN5VD families in 5-pin SOT23-5 packaging. This allows drop-in replacement in existing layouts - provided the alternative part shares the same 2.1V threshold, push-pull output, and timeout behavior. Always verify reset timing and output drive strength in final system validation.

What is the maximum transient duration the MAX6424UK21 can ignore without asserting reset?

The MAX6424UK21 ignores VCC transients ≤50µs in duration when the dip magnitude is ≤100mV below its 2.100V threshold, as shown in the "Maximum Transient Duration vs. Reset Threshold Overdrive" graph. This immunity prevents false resets from switching noise or ESD-induced supply glitches, supporting robust operation in electrically noisy automotive and industrial environments.