Analog Devices Inc./Maxim Integrated MAX6855UK44D4+T

Overview

The MAX6855UK44D4+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring ultra-low 170nA typical supply current, a factory-trimmed 4.375V reset threshold (suffix "44"), and a 1200ms minimum reset timeout (suffix "D4"). It provides active-high push-pull RESET output, manual reset input (MR), and operates across –40°C to +85°C for reliable power-up/brownout monitoring in battery-powered medical and portable electronics.

For engineers reviewing the MAX6855UK44D4+T datasheet, MAX6855UK44D4+T pinout, MAX6855UK44D4+T application, or MAX6855UK44D4+T equivalent, key selection criteria include its precise 4.375V VTH tolerance (±2.5%), guaranteed RESET validity down to VCC = +1.1V, immunity to short VCC transients (<40µs at 100mV overdrive), and compatibility with CMOS-level MR signaling.

Technical Context

This device integrates voltage monitoring, manual reset assertion, and reset timing control - but no watchdog timer (excluded per Selector Guide). Its internal 10kΩ MR pullup enables direct switch-to-GND implementation without external components, while the push-pull active-high RESET output drives µP reset inputs directly without pullup resistors.

The reset assertion logic triggers on VCC falling below 4.375V or MR low, holding RESET high for ≥1200ms after VCC rises above threshold and MR deasserts. Timing is temperature-stable: tRP variation is ±1% over –40°C to +85°C, and VTH drift is <±0.5% across temperature.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5 (lead-free, +T suffix), 2.9mm × 1.6mm footprint, 1.1mm height.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6855UK44D4+T, TPS3837K33DBVR offers lower cost but sacrifices MR functionality and threshold flexibility, while MAX6369KA29D3+T matches the nanopower profile and package but serves lower-voltage applications - making MAX6855UK44D4+T optimal for 4.5V battery systems needing manual reset and long timeout.

Availability

MAX6855UK44D4+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered IoT sensors, and industrial handheld terminals requiring stable component supply with guaranteed long-term availability.

Supply support for MAX6855UK44D4+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 management, sensing, and interface applications in demanding industrial, medical, and communications systems.

The MAX6854–MAX6869 family delivers nanopower supervisory functions specifically for battery-critical applications where µP reliability must be maintained across extreme voltage and temperature conditions.

FAQ

What is the exact reset threshold voltage of the MAX6855UK44D4+T?

The MAX6855UK44D4+T has a factory-trimmed reset threshold voltage of 4.375V, with a guaranteed tolerance of ±2.5% over the full –40°C to +85°C temperature range. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "44" explicitly corresponds to 4.375V (typical), 4.266V (min), and 4.484V (max).

Does the MAX6855UK44D4+T include a watchdog timer function?

No, the MAX6855UK44D4+T does not include a watchdog timer. Per the Selector Guide in the datasheet, only MAX6864–MAX6869 variants feature WDI input and watchdog timeout capability. The MAX6855UK44D4+T is configured exclusively for voltage monitoring and manual reset, with no WDI pin or associated circuitry.

What is the function of Pin 1 on the MAX6855UK44D4+T?

Pin 1 of the MAX6855UK44D4+T is the RESET output terminal, configured as an active-high push-pull driver. As documented in the MAX6854/MAX6855/MAX6856 Pin Description table, it transitions from low to high when VCC drops below 4.375V or MR is pulled low, and remains high for ≥1200ms after VCC exceeds threshold and MR deasserts.

Can the MAX6855UK44D4+T operate with a supply voltage below 1.2V?

No - the absolute minimum specified VCC for functional operation of the MAX6855UK44D4+T is 1.2V, as stated in the Electrical Characteristics table. Although RESET output remains valid down to VCC = +1.1V, the device does not guarantee correct internal operation (e.g., threshold comparison, timing accuracy) below 1.2V.

Is the MR input of the MAX6855UK44D4+T compatible with 1.8V logic levels?

Yes - the MR input of the MAX6855UK44D4+T accepts standard CMOS logic levels: VIL is defined as 0.3×VCC and VIH as 0.7×VCC. At VCC = 1.8V, this translates to VIL ≤ 0.54V and VIH ≥ 1.26V, fully compatible with 1.8V logic families. The internal 10kΩ pullup ensures clean default-high state without external components.