Analog Devices Inc./Maxim Integrated MAX6840XSD0+T

Overview

MAX6840XSD0+T from Maxim Integrated is an ultra-low-voltage, open-drain active-low microprocessor reset circuit in SC70-4 package, designed to monitor supply voltages via external resistive divider at RESET-IN pin with 444mV internal reference. It provides 70µs reset timeout, ±3.0% threshold accuracy over temperature, and operates down to VCC = 1.1V. Used for reliable power-on reset in low-voltage portable systems.

For engineers reviewing the MAX6840XSD0+T datasheet, MAX6840XSD0+T pinout, MAX6840XSD0+T application, or MAX6840XSD0+T equivalent, key selection criteria include its adjustable-threshold architecture, open-drain output compatibility with bidirectional µP reset pins, guaranteed reset validity during VCC decay, and immunity to sub-100ns MR glitches.

Technical Context

The MAX6840XSD0+T uses a precision 444mV internal reference to compare externally divided monitored voltage at RESET-IN; reset asserts when that input falls below threshold. Its open-drain RESET output requires an external pullup and supports level-shifting across supply domains.

It features fixed 70µs timeout (D0 suffix), 7.5µA typical supply current at 1.2V, and operates across -40°C to +85°C. The device ignores fast VCC transients and guarantees reset assertion down to VCC = 1.1V while maintaining RESET-IN threshold accuracy.

Key Specifications

Pinout & Package

MAX6840XSD0+T is housed in a 4-pin SC70-4 package (2.0mm × 2.1mm, 0.65mm pitch), optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage detector and reset supervision applications.

Compared with MAX6840XSD0+T, MAX6837XSD0+T adds manual reset and changes output polarity but retains identical threshold flexibility, while TLV809EADBZR sacrifices adjustability and low-voltage operation for ultra-low current and lower cost in fixed-supply applications.

Availability

MAX6840XSD0+T is available at Aetrix Electronics and suitable for battery-powered wearables, low-voltage IoT sensors, and portable medical devices requiring stable component supply with long-term lifecycle assurance.

Supply support for MAX6840XSD0+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

Maxim Integrated, now part of Analog Devices, designs precision analog and mixed-signal ICs for power, sensing, and connectivity applications.

The MAX6832–MAX6840 family delivers ultra-low-voltage reset supervision for portable and energy-sensitive systems, emphasizing minimal current draw, small footprint, and flexible threshold configuration via RESET-IN.

FAQ

What is the function of the RESET-IN pin on the MAX6840XSD0+T?

The RESET-IN pin on the MAX6840XSD0+T serves as a high-impedance input for an external resistive voltage divider, allowing precise adjustment of the reset threshold. It compares the applied voltage against an internal 444mV reference; reset asserts when RESET-IN falls below this value. This architecture enables monitoring of supply voltages as low as ~0.44V while maintaining accuracy across temperature. The MAX6840XSD0+T does not monitor VCC directly - it relies entirely on the RESET-IN signal for reset generation.

Does the MAX6840XSD0+T have a manual reset (MR) input?

No, the MAX6840XSD0+T does not include a manual reset (MR) input. Unlike variants such as MAX6835XSD0+T or MAX6837XSD0+T, this part is specifically configured for RESET-IN–only operation. Its pinout consists solely of RESET-IN, VCC, GND, and open-drain RESET. If manual reset functionality is required, MAX6837XSD0+T is the direct family alternative with identical RESET-IN capability plus debounced MR support.

What is the guaranteed VCC operating range for the MAX6840XSD0+T?

The MAX6840XSD0+T is specified to operate with VCC from 1.1V to 3.3V. Crucially, the 444mV RESET-IN threshold accuracy (±3.0%) is guaranteed only when VCC ≥ 1.1V - this minimum ensures proper biasing of the internal reference circuitry. Operation below 1.1V is not characterized, and RESET-IN performance cannot be assured. The device draws just 7.5µA typical current at 1.2V, making it ideal for ultra-low-power systems within this validated range.

How does the open-drain RESET output of the MAX6840XSD0+T behave during power-down?

The open-drain RESET output of the MAX6840XSD0+T remains high-impedance (floating) when not asserted, relying on an external pullup resistor to define the inactive state. During power-down, as VCC declines, the output continues sinking current until VCC approaches ~0.55V - below which sink capability degrades. To ensure RESET stays valid down to 0V, a pulldown resistor (e.g., 100kΩ) may be added. The MAX6840XSD0+T's open-drain structure also enables safe wired-OR connection with other reset sources on a shared bus.

What timeout period is implemented in the MAX6840XSD0+T, and how is it selected?

The MAX6840XSD0+T implements a fixed 70µs reset timeout period, indicated by the "D0" suffix in its full ordering code. This timeout is factory-set and non-adjustable; it defines the minimum duration RESET remains asserted after RESET-IN rises above the 444mV threshold. The D0 option is optimized for fast-recovery applications like microcontroller boot sequences where rapid exit from reset is critical. Other timeout options (D1–D4) are available in different variants but require distinct part numbers.