Analog Devices Inc./Maxim Integrated MAX6729KAZED3+

Overview

MAX6729KAZED3+ 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 voltage via RSTIN (626.5mV reference). It provides push-pull active-low reset output (RST), power-fail input/output (PFI/PFO), manual reset (MR), and watchdog timer (WDI) with 35s startup and 1.12s normal timeout. Used in telecom power systems to ensure reliable boot and brownout recovery.

For engineers reviewing the MAX6729KAZED3+ datasheet, MAX6729KAZED3+ pinout, MAX6729KAZED3+ application, or MAX6729KAZED3+ equivalent, key selection factors include its triple-supply monitoring capability, guaranteed reset validity down to VCC1/VCC2 = 0.8V, push-pull RST output referenced to VCC1, PFO with push-pull drive, and factory-trimmed dual-threshold configuration with 210ms (min) reset timeout.

Technical Context

The MAX6729KAZED3+ implements a dual-comparator architecture for independent VCC1 and VCC2 monitoring plus a dedicated high-impedance RSTIN comparator referenced to a 626.5mV internal bandgap. Its reset logic asserts RST low when any monitored supply falls below its threshold or when MR is pulled low, WDI times out, or PFI drops below VPFI - with reset held for a minimum 210ms after all conditions clear.

It integrates a dual-mode watchdog timer: a 35s (min) initial timeout after power-up/manual reset enables full system initialization, followed by a 1.12s (min) normal mode requiring periodic WDI transitions. The PFI/PFO path features 2µs propagation delay and 3mV hysteresis, supporting early power-fail warning and orderly shutdown in multirail systems.

Key Specifications

Pinout & Package

MAX6729KAZED3+ uses an 8-pin SOT23-8 package (2.0mm × 2.1mm × 1.25mm height), optimized for space-constrained PCB layouts in telecom and embedded systems.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triple-voltage supervisory applications.

Compared with MAX6728KAZED3+, MAX6729KAZED3+ offers direct-drive PFO eliminating pullup components, while TPS3808G33DBVR provides lower quiescent current but sacrifices triple-supply capability, watchdog, and power-fail functionality - making MAX6729KAZED3+ the only option meeting full feature requirements for complex multirail systems.

Availability

MAX6729KAZED3+ is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and medical imaging equipment requiring stable component supply, long-term lifecycle support, and guaranteed performance across -40°C to +85°C.

Supply support for MAX6729KAZED3+ 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, automotive, and communications applications.

The MAX6715–MAX6729 family delivers ultra-low-voltage, triple-supply supervisory circuits targeting space-constrained, multirail systems where reliability, low IQ, and integrated watchdog/power-fail functions are essential.

FAQ

What is the exact reset threshold voltage for VCC1 on the MAX6729KAZED3+?

The MAX6729KAZED3+ has a factory-trimmed VCC1 reset threshold of 4.625V (minimum 4.500V, maximum 4.750V) with ±125mV tolerance over temperature. This value is encoded in the "Z" suffix per Maxim's Reset Voltage Threshold Suffix Guide and is verified across the full -40°C to +85°C operating range.

Does the MAX6729KAZED3+ support monitoring a third voltage, and how is it configured?

Yes, the MAX6729KAZED3+ supports third-voltage monitoring via the RSTIN pin, which compares the input against a precise 626.5mV internal reference. An external resistor divider (e.g., R1/R2) sets the trip point: V_{EXT_TH} = 626.5mV × (R1 + R2)/R2. This enables monitoring of supplies as low as 0.62V with minimal current draw due to RSTIN's ±25nA leakage.

What is the function of the PFI and PFO pins on the MAX6729KAZED3+?

PFI is the power-fail input comparator noninverting terminal, referenced to 626.5mV; when PFI falls below this threshold, PFO (active-low) asserts immediately without reset timeout delay. PFO is a push-pull output referenced to VCC1, enabling direct connection to µP interrupt pins or power-control logic for early warning and orderly shutdown.

How does the watchdog timer operate on the MAX6729KAZED3+?

The MAX6729KAZED3+ watchdog operates in two modes: a 35s (min) startup period after reset to allow full system initialization, then a 1.12s (min) normal timeout requiring WDI edge transitions. If WDI remains static beyond the active timeout, RST asserts for 210ms. The timer clears on any rising/falling edge or reset event.

What package type and pin count does the MAX6729KAZED3+ use?

The MAX6729KAZED3+ uses an 8-pin SOT23-8 package (2.0mm × 2.1mm footprint, 1.25mm height) with gull-wing leads. Pinout is fully documented in Maxim's datasheet Figure 1 and Selector Guide, confirming compatibility with standard SOT23-8 reflow profiles and pick-and-place equipment.