Analog Devices Inc./Maxim Integrated MAX6855UK33D3+T

Overview

The MAX6855UK33D3+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 3.3V reset threshold (±2.5%). It delivers ultra-low 170nA typical supply current and guarantees valid reset assertion down to VCC = +1.1V. It is used in battery-powered medical devices like glucose monitors to ensure reliable power-on reset and brownout protection.

For engineers reviewing the MAX6855UK33D3+T datasheet, MAX6855UK33D3+T pinout, MAX6855UK33D3+T application, or MAX6855UK33D3+T equivalent, key selection criteria include its 3.3V reset threshold accuracy, 150ms minimum reset timeout period (D3), active-high push-pull output logic, MR input with 10kΩ internal pullup, and immunity to short VCC transients - all critical for low-power embedded systems requiring deterministic reset behavior under marginal supply conditions.

Technical Context

This device integrates voltage monitoring, manual reset initiation, and reset timing control into a single monolithic BiCMOS IC. Its reset assertion is triggered by VCC falling below 3.3V (±2.5%), MR low pulse ≥1µs, or watchdog timeout - though the MAX6855 variant lacks watchdog functionality. The internal timer ensures reset remains asserted for ≥150ms after VCC rises above threshold and MR deasserts.

The active-high push-pull RESET output is referenced to VCC and sources ≥0.8×VCC at 500µA load when deasserted; it sinks ≤0.3V at 1.2mA when asserted. Guaranteed operation from VCC = 1.2V to 5.5V and full functionality down to 1.1V enables use in deep-brownout scenarios common in portable healthcare electronics.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, lead-free (RoHS-compliant), footprint compatible with industry-standard 5-pin SOT23 layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3837K33DBVR and MAX6315US33D3+, the MAX6855UK33D3+T uniquely combines ultra-low 170nA supply current, active-high push-pull output (no pullup needed), and integrated MR input - making it optimal for next-generation portable medical and consumer devices where battery life, board space, and functional completeness are jointly constrained.

Availability

MAX6855UK33D3+T is available at Aetrix Electronics and suitable for glucose monitors, patient monitors, and MP3 players requiring stable component supply across extended product lifecycles and low-volume production ramps.

Supply support for MAX6855UK33D3+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, mixed-signal, and power management ICs for demanding industrial, medical, and communications applications.

The MAX6855 belongs to Maxim's nanopower µP supervisory family, engineered specifically for battery-critical portable electronics where sub-µA quiescent current, accurate voltage thresholds, and minimal external components are mandatory.

FAQ

What is the exact reset threshold voltage of the MAX6855UK33D3+T?

The MAX6855UK33D3+T has a factory-trimmed reset threshold of 3.300V with ±2.5% tolerance over temperature (−40°C to +85°C). This value is fixed per the "33" suffix in the part number and is verified per Table 2 (Threshold Suffix Guide) in the datasheet. The MAX6855UK33D3+T does not support adjustable or user-programmable thresholds.

Does the MAX6855UK33D3+T include a watchdog timer function?

No, the MAX6855UK33D3+T does not include a watchdog timer. It is part of the MAX6854/MAX6855/MAX6856 series, which provide voltage monitoring and manual reset only. Watchdog functionality is exclusive to MAX6864–MAX6869 variants (e.g., MAX6864UK33D3S+T), identifiable by the "S" or "L" suffix in the ordering code.

What is the function of Pin 1 and Pin 4 on the MAX6855UK33D3+T?

Pin 1 is the active-high push-pull RESET output; it drives high during reset assertion and low otherwise. Pin 4 is a second GND terminal - not NC - and must be connected to the same ground plane as Pin 2 to ensure stable operation, reduce noise coupling, and meet thermal specifications. Both ground pins are internally bonded and required for full performance.

Can the MAX6855UK33D3+T operate reliably below 1.2V?

Yes - the MAX6855UK33D3+T guarantees valid reset assertion down to VCC = +1.1V, though its specified operating range begins at 1.2V. Below 1.2V, the device continues to monitor VCC and assert RESET as long as VCC remains above 1.1V; however, electrical characteristics like VOL and VOH are not guaranteed in this sub-range.

Is the MAX6855UK33D3+T pin-compatible with other SOT23-5 supervisory ICs?

The MAX6855UK33D3+T shares the standard 5-pin SOT23 footprint and pinout (RESET–GND–MR–GND–VCC) with the TPS3836/TPS3837/TPS3838 family, as noted in the datasheet features. However, logic polarity differs: MAX6855UK33D3+T uses active-high RESET, while TPS383x parts use active-low. Direct replacement requires verification of µP reset input polarity and timing compatibility.