Analog Devices Inc./Maxim Integrated MAX6855UK45D1+T

Overview

The MAX6855UK45D1+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, featuring active-high push-pull reset output, manual reset input (MR), and factory-trimmed 4.500V reset threshold with ±2.5% tolerance. It delivers ultra-low 170nA typical supply current at VCC = 1.8V and guarantees valid reset assertion down to VCC = 1.1V. It is designed for battery-powered portable systems requiring reliable power-on reset and brownout protection.

For engineers reviewing the MAX6855UK45D1+T datasheet, MAX6855UK45D1+T pinout, MAX6855UK45D1+T application, or MAX6855UK45D1+T equivalent, key selection criteria include its 4.500V reset threshold accuracy, 10ms minimum reset timeout, active-high push-pull output logic, MR input with internal 10kΩ pullup, and guaranteed operation across –40°C to +85°C.

Technical Context

This device implements a precision voltage monitor with hysteresis (0.5% of VTH) and a fixed 10ms reset timeout timer. The reset output remains asserted for the full timeout period after VCC rises above the 4.500V threshold and MR is deasserted, ensuring stable µP initialization during power-up recovery.

It features a dedicated active-high push-pull RESET output referenced to VCC, eliminating external pullup components. The MR input accepts CMOS-compatible logic levels and includes 200ns glitch rejection and 250ns MR-to-reset delay, enabling robust manual reset triggering without external debounce.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount. Compact footprint (2.9mm × 1.6mm × 1.1mm) suitable for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6855UK45D1+T, the MAX6854UK45D1+T offers identical supervision accuracy and timing but inverted reset polarity, while the TPS3837K45DBVR trades nanopower efficiency for broader TI ecosystem support and slightly relaxed temperature range (–40°C to +125°C).

Availability

MAX6855UK45D1+T is available at Aetrix Electronics and suitable for portable medical devices, industrial handheld scanners, and smart energy meter display modules requiring stable component supply and long-term lifecycle assurance.

Supply support for MAX6855UK45D1+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 high-performance analog, mixed-signal, and power management ICs for industrial, medical, and communications applications.

The MAX685x family was designed specifically for ultra-low-power microprocessor supervision in battery-critical portable equipment, combining precision voltage monitoring, manual reset, and minimal ICC in miniature SOT23 packages.

FAQ

What is the exact reset threshold voltage of the MAX6855UK45D1+T?

The MAX6855UK45D1+T has a factory-trimmed reset threshold of 4.500V with ±2.5% tolerance over –40°C to +85°C, as specified in Table 2 of the datasheet. This value is confirmed by the "45" suffix in the part number and applies to the falling VCC condition. The device guarantees reset assertion when VCC drops below this threshold and holds reset for the full 10ms timeout after VCC recovers.

Does the MAX6855UK45D1+T include a watchdog timer function?

No, the MAX6855UK45D1+T does not include a watchdog timer. Per the Selector Guide and Pin Description sections, only MAX6864–MAX6869 variants feature WDI input and watchdog timeout functionality. The MAX6855UK45D1+T provides voltage monitoring, manual reset input (MR), and fixed 10ms reset timeout - no watchdog circuitry is present.

What is the function of Pin 4 on the MAX6855UK45D1+T?

Pin 4 on the MAX6855UK45D1+T is a second GND terminal, not an I.C. or CT pin. As shown in the MAX6854/MAX6855/MAX6856 Pin Description and Top View diagram, Pins 2 and 4 are both labeled GND and must be connected to the same system ground potential. This dual-GND configuration improves noise immunity and thermal dissipation in the 5-pin SOT23 package.

Can the MAX6855UK45D1+T operate with supply voltages below 1.2V?

No, the MAX6855UK45D1+T has a specified minimum operating VCC of 1.2V per the Absolute Maximum Ratings and Electrical Characteristics tables. Although it guarantees valid reset output down to VCC = 1.1V, functional operation-including accurate threshold detection and timeout timing-is only ensured within the 1.2V to 5.5V range. Operation below 1.2V is outside specification and not recommended.

Is the MR input of the MAX6855UK45D1+T compatible with open-drain logic drivers?

Yes, the MR input of the MAX6855UK45D1+T is fully compatible with open-drain (or open-collector) logic drivers. The internal 10kΩ pullup to VCC ensures proper logic-high state when the driver is inactive, and the MR pin accepts standard CMOS voltage levels (VIH ≥ 0.7×VCC, VIL ≤ 0.3×VCC). No external pullup is needed, and the 200ns glitch rejection protects against noise-induced false resets.