Analog Devices Inc./Maxim Integrated MAX6855UK19D4+T

Overview

MAX6855UK19D4+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in 5-pin SOT23 package, providing active-high push-pull reset output, manual reset input (MR), and factory-trimmed 1.9V reset threshold with 1200ms minimum reset timeout. It monitors VCC down to 1.1V, draws only 170nA typical supply current, and asserts reset during power-up, brownout, or MR activation - ideal for battery-powered glucose monitors and portable medical devices.

For engineers reviewing the MAX6855UK19D4+T datasheet, MAX6855UK19D4+T pinout, MAX6855UK19D4+T application, or MAX6855UK19D4+T equivalent, key selection criteria include its 1.9V threshold accuracy (±2.5%), guaranteed reset validity at VCC = 1.1V, immunity to sub-40µs VCC transients, and compatibility with low-voltage µP reset inputs requiring active-high signaling.

Technical Context

The MAX6855UK19D4+T implements a precision bandgap-based voltage monitor with 2.5% threshold tolerance over -40°C to +85°C, coupled to a monolithic timer that enforces a fixed 1200ms minimum reset assertion after VCC recovery or MR release. Its active-high push-pull RESET output is referenced to VCC and sinks ≤0.3V at 1.2mA load when asserted.

No watchdog timer or CT pin is present - this variant belongs to the MAX6855 subgroup defined by active-high push-pull reset, manual reset input, and absence of WDI/CT functionality. It shares pinout and core supervision logic with MAX6854/MAX6856 but differs in output polarity and drive type.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, surface-mount, lead-free (RoHS-compliant), 2.9mm × 1.6mm footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3837K33DBVR and MAX6315US29D3+, the MAX6855UK19D4+T uniquely delivers 1.9V precision threshold, 1200ms timeout, and active-high push-pull output in one nanopower package - eliminating level-shifting, reducing component count, and extending battery life in sub-2V medical wearables.

Availability

MAX6855UK19D4+T is available at Aetrix Electronics and suitable for portable medical devices, battery-powered patient monitors, and low-power wearable sensors requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MAX6855UK19D4+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 MAX685x family targets ultra-low-power microprocessor supervision in space-constrained, battery-operated systems where nanoscale current draw, guaranteed reset validity at sub-1.2V, and minimal external components are critical design requirements.

FAQ

What is the exact reset threshold voltage of the MAX6855UK19D4+T?

The MAX6855UK19D4+T has a factory-trimmed reset threshold of 1.900V, with guaranteed tolerance of ±2.5% over the full operating temperature range (-40°C to +85°C). This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "19" corresponds to 1.900V nominal. The actual device will assert reset when VCC falls below this threshold during power-down or brownout conditions, and maintain reset until VCC rises above it plus hysteresis.

Does the MAX6855UK19D4+T include a watchdog timer function?

No, the MAX6855UK19D4+T does not include a watchdog timer. It belongs to the MAX6855 subgroup, which provides only voltage monitoring and manual reset (MR) functionality. Watchdog capability is exclusive to MAX6864–MAX6869 variants (e.g., MAX6864UK19D4S+T), identifiable by the "S" or "L" suffix in the part number. The MAX6855UK19D4+T pinout lacks WDI, confirming absence of watchdog circuitry.

What is the function of Pin 4 on the MAX6855UK19D4+T?

Pin 4 on the MAX6855UK19D4+T is a second ground (GND) terminal, not an unused or no-connect pin. Per the MAX6854/MAX6855/MAX6856 Pin Description table and SOT23 top-view diagram, both Pin 2 and Pin 4 are bonded to the internal ground net. Connecting both enhances noise immunity and thermal performance in high-reliability medical applications. Leaving Pin 4 unconnected may degrade reset threshold accuracy under EMI stress.

Can the MAX6855UK19D4+T operate from a 1.5V supply?

Yes, the MAX6855UK19D4+T operates with VCC as low as 1.2V per Absolute Maximum Ratings and Electrical Characteristics tables, and guarantees valid reset output down to VCC = 1.1V. At 1.5V supply, it correctly monitors for drops below 1.9V threshold - however, since 1.5V < 1.9V, the device will assert reset continuously until VCC rises above 1.9V. Thus, it functions reliably as a supervisor for systems where VCC is regulated to ≥1.9V (e.g., 2.0V LDO output), not as a 1.5V rail supervisor.

Is the MAX6855UK19D4+T pin-compatible with the TPS3836 series?

No, the MAX6855UK19D4+T is not pin-compatible with the TPS3836 series. While the datasheet notes pin compatibility for MAX6861/MAX6862/MAX6863 with TPS3836/3837/3838, the MAX6855 uses a different pinout: Pin 1 = RESET (active-high), Pin 3 = MR, Pins 2 & 4 = GND, Pin 5 = VCC. TPS3836 variants place RESET on Pin 1 (open-drain) and MR on Pin 2 - making direct replacement impossible without PCB redesign.