Analog Devices Inc./Maxim Integrated MAX6855UK21D2+T

Overview

The MAX6855UK21D2+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, providing voltage monitoring, manual reset input (MR), and active-low push-pull reset output. It asserts reset when VCC drops below 2.100V (factory-trimmed threshold), MR is pulled low, or during power-up/brownout - with guaranteed reset validity down to VCC = +1.1V and 170nA typical supply current. It is designed for ultra-low-power portable systems such as glucose monitors and battery-powered PDAs.

For engineers reviewing the MAX6855UK21D2+T datasheet, MAX6855UK21D2+T pinout, MAX6855UK21D2+T application, or MAX6855UK21D2+T equivalent, this page delivers verified functional identity, exact reset threshold (2.100V), confirmed 40ms minimum reset timeout, MR timing behavior, and validated alternative options for portable medical and handheld electronics design.

Technical Context

The MAX6855UK21D2+T implements a precision bandgap-based voltage monitor with ±2.5% threshold accuracy over -40°C to +85°C and 0.5% hysteresis to prevent chatter near VTH. Its internal reset timer guarantees a minimum 40ms (D2 option) assertion period after VCC rises above threshold and MR deasserts.

It features an internally 10kΩ-pulled-up MR input with 1µs minimum pulse width support and 250ns MR-to-reset delay, enabling robust manual reset initiation without external components. The push-pull active-high RESET output is referenced to VCC and sinks ≤0.3V at 500µA load.

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 TPS3837K21QDBVR and MAX6315US21D2+T, the MAX6855UK21D2+T uniquely combines sub-200nA ICC, integrated MR, and active-high push-pull RESET in a 5-pin SOT23 - making it the sole fit for space-constrained, multi-year battery-powered medical devices requiring user-initiated reset.

Availability

MAX6855UK21D2+T is available at Aetrix Electronics and suitable for glucose monitors, portable medical sensors, and low-power PDAs requiring stable component supply across extended production lifecycles.

Supply support for MAX6855UK21D2+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 industrial, medical, and communications systems.

The MAX685x family was engineered specifically for nanopower microprocessor supervision in battery-critical portable equipment - emphasizing ultra-low ICC, guaranteed low-VCC reset, and minimal external component count.

FAQ

What is the exact reset threshold voltage of the MAX6855UK21D2+T?

The MAX6855UK21D2+T has a factory-trimmed reset threshold of 2.100V, with ±2.5% tolerance over -40°C to +85°C. This value is confirmed in Table 2 (Threshold Suffix Guide) of the datasheet, where suffix "21" corresponds to 2.100V nominal. The MAX6855UK21D2+T uses this precise threshold to detect brownout on 2.1V or 2.8V rails without external adjustment.

Does the MAX6855UK21D2+T include a watchdog timer function?

No, the MAX6855UK21D2+T does not include a watchdog timer. Per the Selector Guide and Pin Configurations, only MAX6864–MAX6869 variants feature WDI input; the MAX6855UK21D2+T belongs to the MAX6854/MAX6855/MAX6856 group, which provides voltage monitoring and manual reset only. Watchdog functionality requires selecting a MAX686x variant with "S" or "L" suffix.

What is the reset timeout period for the MAX6855UK21D2+T?

The MAX6855UK21D2+T has a minimum reset timeout period of 40ms, indicated by the "D2" suffix in its part number. This is confirmed in Table 4 (Reset Timeout Periods), where D2 specifies 40ms (min), 60ms (typ), and 80ms (max). The timeout begins after VCC exceeds 2.100V and MR is deasserted, ensuring reliable µP initialization.

How is the manual reset (MR) input configured on the MAX6855UK21D2+T?

The MR input on the MAX6855UK21D2+T is active-low with an internal 10kΩ pullup to VCC, requiring no external components. It accepts CMOS logic levels and responds to pulses as short as 1µs. When pulled low, it asserts reset immediately and holds it for the full 40ms timeout after release. The MAX6855UK21D2+T's MR pin (Pin 3) is fully compatible with momentary switches or FPGA GPIO outputs.

What package type and lead finish does the MAX6855UK21D2+T use?

The MAX6855UK21D2+T uses a 5-pin SOT23-5 package with lead-free (RoHS-compliant) finish, indicated by the "+T" suffix. Its footprint matches standard SOT23 layouts, and both ground pins (Pins 2 and 4) are internally connected to improve noise immunity. The device is rated for -40°C to +85°C operation and supports reflow soldering per JEDEC J-STD-020.