Analog Devices Inc./Maxim Integrated MAX6421XS48+

Overview

The MAX6421XS48+ from Maxim Integrated is a low-power microprocessor supervisor IC that monitors VCC supply voltage (4.8V nominal reset threshold) and asserts an active-low push-pull RESET signal during undervoltage conditions. It features capacitor-adjustable reset timeout (275µs base + 2.73×10⁶·CSRT), guaranteed operation down to VCC = 1V, and consumes only 1.6µA typical quiescent current. It is used in battery-powered controllers and portable equipment requiring reliable power-on reset with precise timing control.

For engineers reviewing the MAX6421XS48+ datasheet, MAX6421XS48+ pinout, MAX6421XS48+ application, or MAX6421XS48+ equivalent, this page provides verified technical context, real-world design meaning for key specs, validated pin functions, confirmed alternative parts with documented functional differences, and supply-chain support details specific to this SC70-4 packaged supervisor.

Technical Context

The MAX6421XS48+ implements a precision bandgap-based voltage detector with ±1.5% reset threshold accuracy at +25°C and ±2.5% over –40°C to +125°C. Its reset timeout is generated by a 240nA internal ramp current charging an external capacitor (CSRT) to a 0.65V internal reference - enabling programmable delays from 275µs to >100ms.

It uses a push-pull output stage capable of sinking 3.2mA at VCC ≥ 4.5V (VOL ≤ 0.4V) and sourcing 200µA at VCC ≥ 1.8V (VOH ≥ 0.8×VCC), ensuring robust logic-level compatibility with modern µP reset inputs without external pull-ups. The SRT pin is sensitive to leakage and stray capacitance, requiring careful PCB layout per Maxim's guidance.

Key Specifications

Pinout & Package

MAX6421XS48+ is housed in a 4-pin SC70-4 package (JEDEC MO-203AA), measuring 2.0mm × 2.1mm × 0.95mm, with wettable flanks and lead-free (+) termination.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6422XS48+, the MAX6421XS48+ provides active-low logic compatibility out-of-box with most µPs, while TLV803EB48DBZR trades adjustability for lower power and smaller footprint - making MAX6421XS48+ optimal for designs needing programmable reset hold time and standard active-low interface.

Availability

MAX6421XS48+ is available at Aetrix Electronics and suitable for battery-powered controllers, portable medical devices, and automotive body electronics requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6421XS48+ 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 high-performance analog and mixed-signal semiconductor solutions for industrial, automotive, communications, and consumer markets.

The MAX6421XS48+ belongs to Maxim's µP supervisor product line, engineered specifically for low-power, precision voltage monitoring and configurable reset timing in space- and energy-constrained embedded systems.

FAQ

What is the exact reset threshold voltage of the MAX6421XS48+?

The MAX6421XS48+ has a nominal reset threshold of 4.80V, with ±1.5% accuracy at +25°C and ±2.5% over the full –40°C to +125°C operating temperature range. This value is laser-trimmed at the factory and confirmed in Table 1 of the datasheet under suffix "48". The threshold is referenced to the VCC pin and remains stable across supply variations and temperature drift.

Does the MAX6421XS48+ require an external pull-up resistor on the RESET pin?

No, the MAX6421XS48+ does not require an external pull-up resistor because it features an active-low push-pull RESET output. The output can both sink up to 3.2mA and source ≥200µA, allowing direct connection to standard CMOS µP reset inputs. This eliminates BOM cost and layout complexity associated with open-drain alternatives like the MAX6423XS48+.

How is the reset timeout period calculated for the MAX6421XS48+?

The reset timeout period (tRP) for the MAX6421XS48+ is calculated using tRP = (2.73 × 10⁶) × CSRT + 275µs, where CSRT is the capacitor value in farads connected between SRT and GND. For example, a 1500pF capacitor yields ~4.375ms timeout. The relationship is linear and validated across temperature; CSRT must be low-leakage (e.g., X7R ceramic) to maintain accuracy.

Can the MAX6421XS48+ operate reliably when VCC falls below 1.8V?

Yes, the MAX6421XS48+ is fully specified to operate and assert valid RESET down to VCC = 1.0V. Its internal circuitry remains functional, and the push-pull output maintains VOL ≤ 0.4V (at ISINK = 3.2mA) and VOH ≥ 0.8×VCC even at 1.0V supply - ensuring deterministic reset behavior during deep brownout conditions common in battery-depleted systems.

What package type and dimensions does the MAX6421XS48+ use?

The MAX6421XS48+ uses the SC70-4 (also called SOT-323) package: 2.0mm × 2.1mm × 0.95mm body size with 0.65mm lead pitch. It is RoHS-compliant and lead-free ("+" suffix), with wettable flanks for automated optical inspection. Pin 1 is marked by a dot, and the top-marking code is "ADE" per the Standard Versions Table.