Analog Devices Inc./Maxim Integrated MAX6855UK28D3+T

Overview

The MAX6855UK28D3+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 2.800V reset threshold (suffix "28"). It delivers ultra-low 170nA typical supply current, guarantees valid reset down to VCC = +1.1V, and provides 150ms minimum reset timeout (suffix "D3"). It is used in battery-powered medical and portable electronics to ensure reliable power-on reset and brownout protection.

For engineers reviewing the MAX6855UK28D3+T datasheet, MAX6855UK28D3+T pinout, MAX6855UK28D3+T application, or MAX6855UK28D3+T equivalent, key selection criteria include its active-high push-pull RESET logic, 2.800V threshold accuracy (±2.5%), 150ms timeout tolerance (150–300ms), MR input with 10kΩ internal pullup, and guaranteed operation from -40°C to +85°C.

Technical Context

This device integrates voltage monitoring, manual reset assertion, and reset timing control-without watchdog or CT functionality-into a single BiCMOS IC. Its reset assertion is triggered solely by VCC falling below 2.800V or MR being pulled low, and deassertion occurs only after VCC rises above threshold and the 150ms timeout expires.

The active-high push-pull RESET output is referenced to VCC and sources ≥0.8×VCC at 200µA (for VCC ≥1.71V) or 500µA (for VCC ≥2.38V). Immunity to short VCC transients is ensured via internal hysteresis (0.5% of VTH) and validated transient rejection up to 40µs at 100mV overdrive.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, lead-free, surface-mount, footprint compatible with industry-standard 5-pin SOT23.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3837K28QDBVR and MAX6326UR29+T, the MAX6855UK28D3+T offers the lowest supply current (170nA vs 1.6µA/800nA) and native active-high push-pull output-eliminating external components and reducing standby power in long-life portable devices.

Availability

MAX6855UK28D3+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, MP3 players, and feature phones requiring stable component supply, long-term lifecycle support, and lead-free compliance.

Supply support for MAX6855UK28D3+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 consumer applications.

The MAX6854–MAX6869 family was designed specifically for ultra-low-power microprocessor supervision in battery-critical portable equipment, emphasizing nanoscale current consumption, precise voltage thresholds, and minimal external component count.

FAQ

What is the exact reset threshold voltage of the MAX6855UK28D3+T?

The MAX6855UK28D3+T has a factory-trimmed reset threshold of 2.800V, with 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 "28" corresponds to 2.730V (min), 2.800V (typ), and 2.870V (max). The MAX6855UK28D3+T uses this exact specification.

Does the MAX6855UK28D3+T include a watchdog timer function?

No, the MAX6855UK28D3+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 capability. The MAX6855UK28D3+T belongs to the MAX6854/MAX6855/MAX6856 group, which provides voltage monitoring, manual reset (MR), and fixed reset timeout-but no watchdog circuitry.

What is the function of Pin 4 on the MAX6855UK28D3+T?

Pin 4 on the MAX6855UK28D3+T is a second ground (GND) terminal, electrically connected internally to Pin 2. Its inclusion improves noise immunity, enhances thermal performance, and reduces ground impedance in high-density layouts. Both GND pins must be connected to the same system ground plane per the Typical Operating Circuit and Pin Configurations diagrams.

How does the reset timeout period of the MAX6855UK28D3+T behave across temperature?

The reset timeout period of the MAX6855UK28D3+T is specified as 150ms (min), 225ms (typ), and 300ms (max) at TA = -40°C to +85°C. Figure MAX6854 toc03 shows normalized tRP variation is within ±1.5% across temperature, confirming tight stability. This behavior is inherent to the internal RC timeout generator and applies directly to the D3-suffixed variant like the MAX6855UK28D3+T.

Is the MAX6855UK28D3+T pin-compatible with other devices in the MAX685x family?

Yes, the MAX6855UK28D3+T shares the identical 5-pin SOT23-5 pinout with all MAX6854/MAX6855/MAX6856 variants (e.g., MAX6854UK28D3+T, MAX6856UK28D3+T), differing only in RESET output polarity and drive type. All use Pins 1 (RESET), 2 (GND), 3 (MR), 4 (GND), and 5 (VCC) with identical functions-enabling drop-in replacement where active-high push-pull reset is acceptable.