Analog Devices Inc./Maxim Integrated MAX6729KALTD3

Overview

MAX6729KALTD3 from Maxim Integrated is a triple-voltage microprocessor supervisory circuit in an 8-pin SOT23 package, monitoring VCC1 (4.625V threshold), VCC2 (3.075V threshold), and an auxiliary supply via RSTIN (626.5mV reference). It asserts active-low push-pull reset and power-fail outputs with 210ms minimum timeout, and includes watchdog timer (35s startup / 1.12s normal mode) and manual reset input. Used in telecom power systems requiring reliable brownout detection and orderly shutdown.

For engineers reviewing the MAX6729KALTD3 datasheet, MAX6729KALTD3 pinout, MAX6729KALTD3 application, or MAX6729KALTD3 equivalent, key selection factors include its triple-supply monitoring capability, guaranteed reset validity down to VCC1/VCC2 = 0.8V, push-pull PFO output referenced to VCC1, and factory-trimmed dual-threshold configuration with D3 timeout suffix.

Technical Context

The MAX6729KALTD3 integrates three independent voltage monitors: primary (VCC1), secondary (VCC2), and auxiliary (RSTIN/PFI), each with dedicated comparators and hysteresis. Its dual-mode watchdog uses a 35s minimum startup period followed by 1.12s normal timeout, triggered by WDI edge transitions.

Reset assertion logic combines ORed fault conditions - VCC1/VCC2 undervoltage, RSTIN < 626.5mV, MR low, or watchdog timeout - with a deterministic 210ms minimum reset hold time after all conditions clear. The push-pull RST and PFO outputs are referenced to VCC1 and support 3.2mA sink at 4.5V.

Key Specifications

Pinout & Package

MAX6729KALTD3 is housed in an 8-pin SOT23-8 package (2.0mm × 2.1mm × 1.25mm), thermally enhanced for high-density PCB layouts and compatible with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6729KALTD3, MAX6728KAUTD3 offers identical supervision features but requires external pullup for PFO, while TPS3808G33DBVR reduces functionality to dual-rail monitoring without watchdog or auxiliary input - making MAX6729KALTD3 the only option supporting triple-rail, push-pull PFO, and dual-mode watchdog in SOT23-8.

Availability

MAX6729KALTD3 is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and medical imaging equipment requiring stable component supply, long-term lifecycle assurance, and guaranteed reset validity under brownout conditions.

Supply support for MAX6729KALTD3 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 demanding industrial, automotive, and communications applications, with expertise in power management and reliability-critical supervision.

The MAX6715–MAX6729 family delivers compact, ultra-low-power supervisory solutions for multivoltage systems where simultaneous monitoring of primary, secondary, and auxiliary rails is essential to system integrity.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on MAX6729KALTD3?

The MAX6729KALTD3 has factory-trimmed reset thresholds of 4.625V for VCC1 (±125mV) and 3.075V for VCC2 (±75mV), as indicated by the "KA" suffix per Maxim's Reset Voltage Threshold Suffix Guide. These values are production-tested and guaranteed across -40°C to +85°C, enabling direct replacement of discrete resistor-based supervisors without recalibration. The MAX6729KALTD3 maintains these thresholds with 20ppm/°C tempco.

Does MAX6729KALTD3 support monitoring a third voltage, and how is it configured?

Yes, MAX6729KALTD3 supports third-voltage monitoring via its PFI pin, which uses a 626.5mV internal reference. To monitor an auxiliary supply, connect PFI to a resistor-divider network from the target rail to GND. The trip point is calculated as V_TRIP = 626.5mV × (R1 + R2)/R2. Unlike RSTIN variants, MAX6729KALTD3 uses PFI (not RSTIN) for this function, and asserts PFO - not RST - when the condition is met.

What is the function of the PFO output on MAX6729KALTD3, and how does it differ from RST?

The PFO output on MAX6729KALTD3 is an active-low push-pull power-fail signal that asserts independently of the reset state when PFI falls below 626.5mV. Unlike RST, PFO deasserts immediately when PFI rises above threshold - with no timeout delay - making it ideal for real-time power-fail interrupts. MAX6729KALTD3's PFO is referenced to VCC1 and can source/sink up to 800µA, eliminating need for external pullups.

How does the watchdog timer operate on MAX6729KALTD3, and what are its timing modes?

MAX6729KALTD3 implements a dual-mode watchdog: a 35s minimum startup period after any reset event (power-up, MR, or watchdog timeout), followed by a 1.12s minimum normal timeout. The timer clears on any WDI edge transition. This architecture prevents false timeouts during boot while enabling rapid fault detection during runtime. MAX6729KALTD3's WDI accepts CMOS/TTL logic and rejects glitches under 100ns.

Is MAX6729KALTD3 compatible with systems requiring reset assertion below 1.0V supply voltage?

Yes, MAX6729KALTD3 guarantees valid reset output logic states down to VCC1 or VCC2 = 0.8V, verified across temperature and process corners. Its internal comparators and push-pull drivers remain functional in deep brownout, unlike many supervisors that release reset prematurely. This allows safe operation in battery-powered systems where supply decays gradually, and ensures deterministic behavior during uncontrolled power loss scenarios.