Analog Devices Inc./Maxim Integrated MAX6865UK33D4S+T

Overview

The MAX6865UK33D4S+T from Maxim Integrated is a nanopower microprocessor supervisory circuit in a 5-pin SOT23 package, combining voltage monitoring, manual reset input (MR), and watchdog timer (WDI) functionality. It asserts an active-high push-pull RESET output when VCC drops below 3.3V (±2.5%), MR is pulled low, or the watchdog expires after 3.3s (typ). Designed for ultra-low-power systems, it draws only 170nA (typ) at 2.5V and guarantees valid reset down to VCC = 1.1V.

For engineers reviewing the MAX6865UK33D4S+T datasheet, MAX6865UK33D4S+T pinout, MAX6865UK33D4S+T application, or MAX6865UK33D4S+T equivalent, key selection criteria include its 3.3V reset threshold, 1200ms minimum reset timeout (D4), 3.3s watchdog period (S suffix), active-high push-pull output, and SOT23-5 footprint compatibility with TPS383x series.

Technical Context

This device integrates a precision bandgap-based voltage monitor, a monostable watchdog timer cleared by WDI edges, and a manual reset input with internal 10kΩ pullup. The reset assertion logic combines three independent triggers-VCC undervoltage, MR low, or WDI timeout-with a fixed 1200ms (min) reset hold time after recovery.

Its BiCMOS process enables guaranteed operation from 1.2V to 5.5V supply, immunity to sub-40µs VCC transients at 100mV overdrive, and stable reset timing across –40°C to +85°C. The active-high push-pull RESET output sources up to 500µA at VCC ≥ 2.38V while maintaining VOH ≥ 0.8×VCC.

Key Specifications

Pinout & Package

Package: 5-pin SOT23-5, 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 TPS3836K33DBVR and MAX6369KA29+T, the MAX6865UK33D4S+T uniquely delivers integrated watchdog timing, manual reset, and extended 1200ms reset hold-all in the same SOT23-5 package-making it optimal for safety-critical or unattended embedded systems requiring autonomous recovery.

Availability

MAX6865UK33D4S+T is available at Aetrix Electronics and suitable for battery-powered medical devices, industrial sensor nodes, portable consumer electronics, and low-power IoT edge devices requiring stable component supply with long-term lifecycle support.

Supply support for MAX6865UK33D4S+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 MAX68xx family was designed specifically for nanopower microprocessor supervision in space- and energy-constrained systems, emphasizing ultra-low ICC, precise reset thresholds, and integrated watchdog/monitoring functions.

FAQ

What is the exact reset threshold voltage of the MAX6865UK33D4S+T?

The MAX6865UK33D4S+T has a factory-trimmed reset threshold of 3.3V with ±2.5% tolerance (3.218V to 3.383V), as indicated by the "33" suffix in the part number per Maxim's Threshold Suffix Guide. This value is guaranteed over –40°C to +85°C and applies to VCC falling conditions.

Does the MAX6865UK33D4S+T support active-low reset output?

No - the MAX6865UK33D4S+T features an active-high push-pull RESET output (pin 1), as confirmed by its "K" reset output type designation in Maxim's Selector Guide and functional diagram. It does not offer open-drain or active-low variants; alternative parts like MAX6866UK33D4S+T provide open-drain active-low output.

What does the "D4S" suffix in MAX6865UK33D4S+T signify?

The "D4" denotes a 1200ms minimum reset timeout period (per Table 4), and "S" specifies a 3.3s typical watchdog timeout period (per Table 3). Together, D4S defines the timing behavior: RESET remains asserted for ≥1200ms after recovery, and WDI must toggle at least every ~3.3s to prevent watchdog expiration.

Can the MAX6865UK33D4S+T operate with VCC below 1.2V?

No - the absolute minimum operating VCC is 1.2V per Electrical Characteristics (TA = –40°C to +85°C). Although RESET remains valid down to VCC = 1.1V, the device does not guarantee functional operation below 1.2V, and supply current specs are not characterized below this limit.

Is the MR input of the MAX6865UK33D4S+T compatible with 1.8V logic?

Yes - the MR input accepts VIH ≥ 0.7×VCC and VIL ≤ 0.3×VCC, so with VCC = 3.3V, it reliably recognizes 1.8V as a valid high-level signal (1.8V > 2.31V threshold not required). Its 10kΩ internal pullup ensures robust idle-state biasing without external components.