Analog Devices Inc./Maxim Integrated MAX6837FXSD3+T

Overview

MAX6837FXSD3+T from Maxim Integrated is an ultra-low-voltage, open-drain active-low microprocessor reset circuit in SC70-4 package, designed to monitor +1.05V supply rails with ±2.5% threshold accuracy over temperature and assert reset for 210ms after VCC recovery or manual reset release. It features debounced MR input, 7.5µA typical supply current, and guaranteed RESET validity down to VCC = 0.55V - used in portable battery-powered µP systems requiring reliable brownout detection.

For engineers reviewing the MAX6837FXSD3+T datasheet, MAX6837FXSD3+T pinout, MAX6837FXSD3+T application, or MAX6837FXSD3+T equivalent, key selection criteria include its 1.05V factory-set reset threshold, 210ms timeout period (D3 suffix), open-drain output requiring external pullup, debounced manual reset input, and compatibility with low-voltage core supplies in space-constrained embedded designs.

Technical Context

The MAX6837FXSD3+T implements a precision voltage comparator with 444mV internal reference, comparing VCC against a factory-trimmed 1.05V threshold (F suffix) with hysteresis of 0.75% of VTH. Its reset logic asserts active-low RESET for a fixed 210ms timeout after VCC rises above threshold or MR transitions high.

It integrates a 20kΩ internal MR pullup resistor, supports MR glitch rejection up to 100ns, and maintains valid open-drain RESET output down to VCC = 0.55V with 0.2V VOL at 200µA sink current. The device operates across -40°C to +85°C and consumes only 7.5µA at 1.2V.

Key Specifications

Pinout & Package

MAX6837FXSD3+T is housed in a 4-pin SC70-4 package (2.0mm × 2.1mm, 0.65mm pitch), optimized for high-density PCB layouts in portable electronics.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6837FXSD3+T, MAX6381XR22D3+T serves higher-voltage rails but omits MR and requires pinout redesign, while TPS3123E10DBVR reduces footprint and cost but sacrifices MR debounce, deep-brownout validity, and temperature accuracy - making MAX6837FXSD3+T optimal for precision 1.05V core supervision with field-service reset capability.

Availability

MAX6837FXSD3+T is available at Aetrix Electronics and suitable for portable medical devices, industrial wireless sensors, and battery-powered handheld instrumentation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MAX6837FXSD3+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) is a semiconductor company specializing in analog, mixed-signal, and power-management ICs for industrial, automotive, and computing applications.

MAX6837FXSD3+T belongs to the MAX6832–MAX6840 family of ultra-low-voltage reset supervisors, engineered specifically for reliable power-on reset and brownout protection in sub-1.2V digital systems with stringent power and space constraints.

FAQ

What is the exact reset threshold voltage of MAX6837FXSD3+T and how is it trimmed?

The MAX6837FXSD3+T has a factory-trimmed reset threshold of 1.050V with ±2.5% accuracy over -40°C to +85°C, specified by the 'F' suffix in the part number. This value is laser-trimmed during wafer test to match the internal 444mV reference and resistive divider network, eliminating need for external calibration. The threshold remains stable across temperature due to matched thermal coefficients in the BiCMOS process.

Does MAX6837FXSD3+T support manual reset, and what are its electrical characteristics?

Yes, MAX6837FXSD3+T includes a debounced manual reset (MR) input with internal 20kΩ pullup to VCC. MR accepts CMOS-compatible logic levels (VIL ≤ 0.3×VCC, VIH ≥ 0.7×VCC), requires minimum 2µs pulse width, and rejects glitches up to 100ns. When pulled low, MR forces active reset for the full 210ms timeout after release - no external debounce components are needed.

What is the purpose of the open-drain RESET output in MAX6837FXSD3+T, and what pullup voltage should be used?

The open-drain RESET output in MAX6837FXSD3+T enables level-shifting and bidirectional reset interfacing - e.g., connecting directly to a µP's bidirectional reset pin with a single pullup. The pullup can be connected to any voltage between 0V and 6V (including supplies higher than VCC), allowing reset signaling across different voltage domains. Typical pullup values range from 10kΩ to 100kΩ depending on rise-time and bus capacitance.

How does MAX6837FXSD3+T behave when VCC drops below 0.55V, and is external circuitry needed?

Below VCC = 0.55V, MAX6837FXSD3+T's open-drain RESET output ceases sinking current and becomes high-impedance. To ensure RESET remains asserted (LOW) down to 0V, a 100kΩ pulldown resistor to GND is recommended - this prevents floating states in systems where µP reset must stay active through complete power collapse. This configuration is validated in Maxim's Figure 3 application circuit.

Is MAX6837FXSD3+T pin-compatible with other members of the MAX6832–MAX6840 family?

MAX6837FXSD3+T shares identical SC70-4 pinout (GND, RESET, MR, VCC) with MAX6835 and MAX6836 variants, enabling drop-in substitution within the same package and pin count. However, it is not pin-compatible with 3-pin SC70-3 versions (e.g., MAX6832–MAX6834) or RESET-IN variants (MAX6838–MAX6840), which use different pin assignments and functions.