Analog Devices Inc./Maxim Integrated MAX6423XS46+

Overview

MAX6423XS46+ from Maxim Integrated is a low-power microprocessor supervisor IC that monitors VCC supply voltage and asserts an active-low open-drain RESET signal when voltage falls below 4.625V (±2.5% over temperature), with capacitor-adjustable reset timeout and guaranteed operation down to VCC = 1V. It features 1.6µA typical quiescent current, 4-pin SC70-4 package, and is designed for critical µP monitoring in portable, automotive, and medical equipment.

For engineers reviewing the MAX6423XS46+ datasheet, MAX6423XS46+ pinout, MAX6423XS46+ application, or MAX6423XS46+ equivalent, key selection criteria include reset threshold accuracy (±2.5% over -40°C to +125°C), open-drain output compatibility with mixed-voltage systems, capacitor-set timeout flexibility, and guaranteed reset validity at VCC ≥ 1V.

Technical Context

The MAX6423XS46+ implements a precision bandgap-based voltage comparator with laser-trimmed resistors to set the 4.625V reset threshold, coupled to a 240nA internal ramp current source that charges an external capacitor on the SRT pin to generate the reset timeout delay. Its open-drain RESET output requires an external pullup and supports logic-level interfacing across supplies up to 5.5V.

It operates over full industrial temperature range (-40°C to +125°C) with supply voltage range 1.0V to 5.5V, exhibits immunity to short VCC transients (e.g., ≤50µs for 100mV overdrive), and ensures monotonic reset assertion/deassertion without false pulses during VCC ramping - critical for reliable power-up sequencing in embedded controllers.

Key Specifications

Pinout & Package

The MAX6423XS46+ is housed in a 4-pin SC70-4 package (2.0mm × 1.25mm, 0.5mm pitch), optimized for high-density portable designs. Pin 1 is SRT (Set Reset Timeout), Pin 2 is GND, Pin 3 is not internally connected (N.C.), and Pin 4 is VCC. The open-drain RESET output is not assigned to a dedicated pin in this variant - it shares functionality with the SRT pin configuration per datasheet pin mapping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6423US46-T, the MAX6423XS46+ offers superior board-area efficiency in ultra-compact designs; versus TLV803EC46DBZR, it provides essential design flexibility through user-adjustable reset timing and open-drain interoperability - critical for systems requiring coordinated multi-rail reset sequencing or legacy µP compatibility.

Availability

MAX6423XS46+ is available at Aetrix Electronics and suitable for battery-powered medical monitors, automotive body control modules, and industrial handheld scanners requiring stable component supply, long-term lifecycle support, and lead-free compliance.

Supply support for MAX6423XS46+ 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and computing applications.

The MAX6421–MAX6426 product line delivers ultra-low-power, capacitor-programmable reset supervisors targeting space- and energy-constrained embedded systems where precise brownout protection and flexible timing are mandatory.

FAQ

What is the exact reset threshold voltage of the MAX6423XS46+ and how does it vary with temperature?

The MAX6423XS46+ has a nominal reset threshold of 4.625V, with tolerance of ±2.5% over the full operating temperature range of -40°C to +125°C. This specification is guaranteed by design and verified across temperature extremes - not just at +25°C. The device uses laser-trimmed resistors and a stable bandgap reference to minimize drift, and typical normalized threshold variation is less than ±0.5% across temperature, as shown in Figure toc08 of the datasheet. This ensures consistent brownout detection in automotive and industrial environments.

How do I calculate the external capacitor value needed to achieve a specific reset timeout period for the MAX6423XS46+?

To set a desired reset timeout period tRP (in seconds) for the MAX6423XS46+, use the formula CSRT = (tRP − 275µs) / 2.73×10⁶, where CSRT is in farads. For example, a 200ms timeout requires CSRT = (0.2 − 0.000275) / 2,730,000 ≈ 73pF. The datasheet specifies ceramic capacitors with leakage <10nA; X7R or C0G types are recommended. Note that timing accuracy depends on capacitor tolerance and board leakage - keep SRT traces short and away from noisy signals to maintain precision.

Can the MAX6423XS46+ drive a reset input directly, or does it require external components?

The MAX6423XS46+ requires an external pullup resistor on its open-drain RESET output to function correctly. Since it lacks an internal pullup, a resistor (typically 10kΩ to 100kΩ) must connect the RESET node to the target µP's logic supply (e.g., 3.3V or 5V). This ensures a valid logic-high level when RESET is deasserted. The value balances leakage current (smaller R increases power) and rise time (larger R slows edge). No other external components are needed for basic operation - the SRT capacitor and pullup resistor constitute the complete external BOM.

Is the NC pin (Pin 3) on the MAX6423XS46+ safe to leave floating, or should it be grounded?

Pin 3 of the MAX6423XS46+ is explicitly designated "Not Internally Connected" (N.C.) in the datasheet and may be safely left floating. However, grounding Pin 3 is recommended for mechanical stability and to reduce potential noise coupling in high-density layouts. Since it is unconnected internally, grounding introduces no electrical side effects - no current flows, no timing impact, and no functional change. Do not connect it to VCC or any active signal; GND is the only appropriate external connection if used.

Does the MAX6423XS46+ remain functional and assert reset correctly when VCC drops below 1.6V?

Yes - the MAX6423XS46+ is fully specified to operate and assert a valid reset signal down to VCC = 1.0V, as confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables. Its internal comparator and ramp generator maintain functionality at 1V, and the open-drain output remains capable of sinking sufficient current (≥50µA) to hold a logic-low state. This capability is critical for detecting deep brownouts in single-cell battery systems, where voltage can fall to 1.0V before cutoff. Below 1.0V, behavior is not guaranteed.