Analog Devices Inc./Maxim Integrated MAX6424UK21+T

Overview

MAX6424UK21+T from Analog Devices is a low-power microprocessor supervisor IC with active-low push-pull reset output, 2.100V ±2.5% factory-trimmed reset threshold, capacitor-adjustable reset timeout (2.73×10⁶ × CSRT + 275µs), and guaranteed operation down to VCC = 1V. It monitors supply voltage in portable battery-powered systems and asserts reset during brownout or power-up sequencing.

For engineers reviewing the MAX6424UK21+T datasheet, MAX6424UK21+T pinout, MAX6424UK21+T application, or MAX6424UK21+T equivalent, key selection criteria include reset threshold accuracy over temperature, quiescent current at ultra-low VCC, SRT pin ramp current stability, and compatibility with 5-pin SOT23-5 PCB layouts for embedded controller supervision.

Technical Context

The MAX6424UK21+T implements a precision voltage detector using laser-trimmed resistors and a 0.65V internal reference, with hysteresis of 4×VTH (≈8.4mV at 2.1V). Its reset assertion logic is triggered by VCC falling below the 2.100V threshold, and deassertion requires both VCC rising above threshold and the external SRT capacitor charging to 0.65V via a 240nA current source.

Unlike open-drain variants, the push-pull output drives RESET low actively and high actively-enabling direct interface to CMOS µP reset inputs without pull-up resistors. The device guarantees valid RESET output down to VCC = 1.0V, supporting brownout detection in low-voltage microcontroller applications.

Key Specifications

Pinout & Package

MAX6424UK21+T is housed in a 5-pin SOT23-5 package with exposed pad (RoHS-compliant lead-free). Pin 1 is SRT (Set Reset Timeout), Pin 2 is GND, Pin 3 is RESET (active-low push-pull), Pin 4 is N.C. (not internally connected), and Pin 5 is VCC. The N.C. pin must not be connected to avoid parasitic coupling.

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+T provides field-tunable reset timing, push-pull drive eliminating external components, and superior low-VCC reset validity-making it optimal for battery-constrained, safety-aware, or timing-flexible designs.

Availability

MAX6424UK21+T is available at Aetrix Electronics and suitable for portable medical sensors, automotive body control modules, and industrial PLC I/O subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6424UK21+T 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The MAX6424UK21+T belongs to the MAX6340/MAX6421–MAX6426 family of ultra-low-power microprocessor supervisors, designed specifically for reliable power-monitoring in battery-operated and harsh-environment embedded systems.

FAQ

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

The MAX6424UK21+T 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 means the actual threshold falls between 2.048V and 2.153V at room temperature, and between 2.048V and 2.153V across temperature extremes-ensuring consistent brownout detection without recalibration.

Can the MAX6424UK21+T operate reliably when VCC drops below 1.8V?

Yes-the MAX6424UK21+T guarantees valid RESET output down to VCC = 1.0V. At VCC = 1.2V, RESET remains functional with VOL ≤ 0.3V (ISINK = 500µA) and VOH ≥ 0.8×VCC, enabling robust supervision of ultra-low-voltage microcontrollers and energy-harvesting systems where supply collapse is gradual.

How do I calculate the external capacitor value needed for a 4.0ms reset timeout with the MAX6424UK21+T?

Use the formula CSRT = (tRP − 275µs) / 2.735×10⁶, where tRP is in seconds. For 4.0ms: CSRT = (0.004 − 0.000275) / 2,735,000 ≈ 1362pF. A standard 1300pF or 1500pF X7R ceramic capacitor yields 3.91ms or 4.375ms timeout-both within datasheet tolerance and suitable for most µP boot requirements.

Is the N.C. pin on the MAX6424UK21+T safe to connect to ground?

Pin 4 of the MAX6424UK21+T is explicitly designated N.C. (Not Internally Connected) and contains no internal circuitry. It may be left floating or connected to GND solely for mechanical reinforcement or thermal relief-however, routing signals or power near it must be avoided to prevent parasitic coupling into the sensitive SRT node.

Does the MAX6424UK21+T require a decoupling capacitor on the VCC pin?

Yes-a 0.1µF ceramic decoupling capacitor placed as close as possible to the VCC pin (Pin 5) and GND (Pin 2) is mandatory. This stabilizes the internal reference and prevents false resets caused by supply noise or fast transients, especially critical in automotive and industrial environments where VCC ripple exceeds 10mVpp.