Analog Devices Inc./Maxim Integrated MAX6728KATGD3+T

Overview

MAX6728KATGD3+T from Maxim Integrated is a triple-voltage microprocessor supervisory circuit in an 8-pin SOT23 package, monitoring VCC1 (primary), VCC2 (secondary), and PFI (power-fail input) with factory-trimmed thresholds of 4.625V (VTH1), 3.075V (VTH2), and 626.5mV (VPFI). It provides open-drain active-low RST and PFO outputs, 210ms (min) reset timeout, and operates from -40°C to +85°C. It is used in telecom power systems to ensure reliable boot sequencing and brownout recovery.

For engineers reviewing the MAX6728KATGD3+T datasheet, MAX6728KATGD3+T pinout, MAX6728KATGD3+T application, or MAX6728KATGD3+T equivalent, key selection criteria include its triple-supply monitoring capability, guaranteed reset validity down to VCC1/VCC2 = 0.8V, PFI/PFO power-fail alerting without reset timeout, and compatibility with low-noise industrial and battery-operated embedded systems requiring deterministic fault response.

Technical Context

The MAX6728KATGD3+T integrates three independent voltage comparators: one for VCC1 (4.625V threshold), one for VCC2 (3.075V), and one for PFI (626.5mV reference), each feeding into a shared reset timeout timer. Its open-drain RST output asserts when any monitored supply falls below its threshold and remains asserted for ≥210ms after all supplies recover.

Unlike dual-monitor variants, MAX6728KATGD3+T includes dedicated PFI/PFO functionality - PFI accepts an external resistor-divider to monitor auxiliary rails (e.g., battery or pre-regulated input), and PFO deasserts immediately upon recovery without timeout delay, enabling fast power-fail interrupt signaling to µP while maintaining system reset integrity via RST.

Key Specifications

Pinout & Package

MAX6728KATGD3+T is housed in an 8-pin SOT23 package (3.0mm × 1.7mm × 1.3mm height), optimized for space-constrained applications. Pin functions are electrically isolated per internal comparator domains and support mixed-rail supervision without cross-coupling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6728KATGD3+T, MAX6729KA+T offers push-pull drive for simplified interface but sacrifices design flexibility in noise-prone environments where open-drain with configurable pullup is preferred; TPS3808G33DBVR reduces feature set and pin count but lacks the critical third-monitoring channel required for power-fail alerting in battery-backed systems.

Availability

MAX6728KATGD3+T is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and battery-powered IoT gateways requiring stable component supply, long-term lifecycle assurance, and guaranteed lead-free compliance.

Supply support for MAX6728KATGD3+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, communications, and computing markets.

The MAX6715–MAX6729 family was designed specifically for ultra-low-voltage, multirail microprocessor supervision in space- and power-constrained systems - emphasizing guaranteed operation down to 0.8V, minimal quiescent current, and flexible monitoring of primary, secondary, and auxiliary supplies.

FAQ

What is the exact reset threshold voltage for VCC1 on the MAX6728KATGD3+T?

The MAX6728KATGD3+T has a factory-trimmed VCC1 reset threshold of 4.625V (with ±125mV tolerance over temperature), as indicated by the "T" suffix in the Reset Voltage Threshold Suffix Guide. This value is laser-trimmed during production and guaranteed across the full -40°C to +85°C operating range, ensuring consistent brownout detection for 5V system rails.

Does the MAX6728KATGD3+T provide a reset timeout for the PFO output?

No, the MAX6728KATGD3+T does not apply reset timeout to the PFO output. PFO asserts low when PFI falls below 626.5mV and deasserts immediately upon PFI rising above threshold - with only 2µs typical propagation delay. This behavior enables real-time power-fail interrupts without delay, unlike the RST output which holds for ≥210ms after recovery.

Can the MAX6728KATGD3+T monitor a negative supply voltage?

Yes, the MAX6728KATGD3+T can monitor negative supplies using the PFI input with an appropriate resistor-divider configuration as shown in Figure 3b of the datasheet. When the negative rail drops, PFO goes high - providing a logic-compatible alert signal. Accuracy depends on PFI threshold tolerance (±15.5mV), resistor matching, and VCC stability, but the architecture supports this use case without modification.

What is the function of Pin 8 (NC) on the MAX6728KATGD3+T?

Pin 8 on the MAX6728KATGD3+T is a no-connect (NC) terminal - internally unconnected and unused. It must be left floating or tied to GND per PCB layout best practices to avoid parasitic coupling; it is not intended for thermal relief or mechanical anchoring. This pin exists due to the 8-pin SOT23 package variant shared across the MAX6725–MAX6729 family.

How does the MAX6728KATGD3+T handle short VCC transients?

The MAX6728KATGD3+T is immune to short negative-going VCC transients up to 20µs duration when the overdrive is 100mV below threshold (per Typical Operating Characteristics graph toc06). This built-in glitch rejection prevents spurious resets during switching noise or ESD events, eliminating need for additional RC filtering on VCC lines in most industrial deployments.