Analog Devices Inc./Maxim Integrated MAX6840XSD0

Overview

MAX6840XSD0 from Maxim Integrated is an ultra-low-voltage microprocessor supervisory circuit with open-drain active-low reset output, adjustable reset threshold via RESET-IN pin (typical 444mV), and 70µs timeout period. It monitors supply voltages as low as 1.1V, consumes only 7.5µA typical supply current, and operates over –40°C to +85°C - designed for reliable power-on reset in portable battery-powered systems.

For engineers reviewing the MAX6840XSD0 datasheet, MAX6840XSD0 pinout, MAX6840XSD0 application, or MAX6840XSD0 equivalent, this device serves as a precision voltage detector and reset generator where external threshold adjustment, low quiescent current, and SC70-4 packaging are critical selection criteria.

Technical Context

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

It features ±3.0% RESET-IN threshold accuracy over temperature, 100ns MR glitch rejection (though MR is not present on MAX6840XSD0), and guaranteed reset validity down to VCC = 0.55V. The 70µs timeout (D0 suffix) is implemented as a fixed propagation delay rather than a capacitor-based timer.

Key Specifications

Pinout & Package

MAX6840XSD0 is housed in a 4-pin SC70 package (1.25mm × 0.85mm, 0.65mm pitch), with gull-wing leads and exposed pad option available per Maxim's lead-free specification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6840XSD0, MAX6837XSD0 trades RESET-IN adjustability for manual reset capability and fixed threshold, while TLV803EA29DBZR offers lower current and simpler packaging at the expense of voltage range flexibility and speed - making MAX6840XSD0 uniquely suited for sub-1.2V, externally programmable, fast-response supervision.

Availability

MAX6840XSD0 is available at Aetrix Electronics and suitable for battery-powered IoT sensors, wearable health monitors, low-voltage FPGA configuration circuits, and industrial microcontroller power supervision requiring stable component supply and long-term lifecycle support.

Supply support for MAX6840XSD0 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 management, sensing, and interface applications in industrial, automotive, and computing markets.

The MAX6832–MAX6840 family was developed to provide ultra-low-voltage, low-quiescent-current supervisory circuits for next-generation portable and energy-constrained systems operating below 1.2V.

FAQ

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

The RESET-IN pin on the MAX6840XSD0 is a high-impedance analog input that connects to an external resistor divider network. It compares the applied voltage against an internal 444mV reference; when the voltage drops below this threshold, the device asserts its open-drain RESET output. This allows precise, user-defined reset trip points - for example, configuring MAX6840XSD0 to monitor a 0.9V supply by setting the divider ratio accordingly. The RESET-IN pin enables flexible voltage detection without requiring multiple fixed-threshold variants.

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

No, the MAX6840XSD0 does not include a manual reset (MR) input. Unlike MAX6835/MAX6836/MAX6837 variants in the same family, MAX6840XSD0 replaces MR with the RESET-IN pin for adjustable threshold monitoring. Its pinout consists solely of RESET-IN, VCC, GND, and open-drain RESET. If manual reset functionality is required, MAX6837XSD0 - which shares the same SC70-4 package and 70µs timeout but includes MR - should be considered as an alternative.

What is the minimum VCC required for accurate operation of the MAX6840XSD0?

The MAX6840XSD0 requires a minimum VCC of 1.1V to guarantee RESET-IN threshold accuracy within ±3.0% over temperature. While the device may power up at lower voltages (down to 0.55V), the 444mV reference and comparator performance are only specified and tested for accuracy when VCC ≥ 1.1V. Operating below this level risks threshold drift and inconsistent reset assertion - so system design must ensure VCC reaches 1.1V before relying on RESET-IN monitoring in the MAX6840XSD0.

Can the MAX6840XSD0's RESET output drive a 3.3V logic input directly?

Yes, the MAX6840XSD0's open-drain RESET output can interface directly with a 3.3V logic input, provided an external pullup resistor connects RESET to the 3.3V rail. Since the output is open-drain, it does not source current - it only sinks current when asserted (LOW). The MAX6840XSD0 guarantees sinking capability up to 200µA at VCC ≥ 1.5V, and the RESET pin tolerates voltages up to 6.0V, making 3.3V pullup fully compatible. This level-shifting capability is a key design advantage of the MAX6840XSD0 in mixed-voltage systems.

How does the 70µs timeout period of the MAX6840XSD0 differ from longer timeouts like 30ms or 210ms?

The 70µs timeout in the MAX6840XSD0 is a fixed propagation delay - not a timed reset pulse - making it functionally a voltage detector rather than a traditional reset supervisor. It asserts RESET almost immediately upon threshold violation and releases it shortly after the monitored voltage recovers, unlike longer timeouts (e.g., 30ms) that hold RESET active for a fixed duration regardless of supply stability. This makes MAX6840XSD0 ideal for fast fault detection in DC/DC converter feedback loops or real-time supply monitoring, where rapid response outweighs extended reset hold time.