Analog Devices Inc./Maxim Integrated MAX6728KAZWD3+T

Overview

MAX6728KAZWD3+T from Maxim Integrated is a triple-voltage microprocessor supervisory circuit in an 8-pin SOT23 package, monitoring VCC1 (1.62V threshold), VCC2 (2.313V threshold), and PFI (626.5mV threshold) with push-pull RST and open-drain PFO outputs, 210ms reset timeout, and watchdog timer - used in telecom power management to ensure reliable boot and brownout recovery.

For engineers reviewing the MAX6728KAZWD3+T datasheet, MAX6728KAZWD3+T pinout, MAX6728KAZWD3+T application, or MAX6728KAZWD3+T equivalent, key selection criteria include triple-supply monitoring capability, guaranteed reset validity down to VCC = 0.8V, integrated power-fail comparator with PFO output, and 35s startup + 1.12s normal watchdog timeout modes.

Technical Context

The MAX6728KAZWD3+T implements dual independent voltage comparators for VCC1 and VCC2, plus a dedicated power-fail comparator referenced to a 626.5mV internal bandgap, all feeding a shared reset timeout timer with 210ms minimum assertion period. Its watchdog logic features a two-phase architecture: 35s minimum initial timeout after any reset event, then automatic transition to 1.12s minimum normal-mode timeout upon first WDI edge detection.

This device integrates a 50kΩ internal MR pullup, supports manual reset assertion via active-low MR input, and guarantees valid reset output state as long as either VCC1 or VCC2 remains ≥ 0.8V - enabling robust operation during deep brownout conditions common in battery-backed telecom systems.

Key Specifications

Pinout & Package

MAX6728KAZWD3+T is housed in an 8-pin SOT23-8 package (3.0mm × 1.7mm × 1.3mm), surface-mount, lead-free (+T suffix), with thermal pad exposed on bottom for enhanced power dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6729KAZWD3+T, MAX6728KAZWD3+T offers open-drain PFO for flexible interfacing but requires external pullup; versus TPS3808G33DBVR, it adds critical third-supply monitoring, programmable PFI threshold, and dual-mode watchdog - making it indispensable for telecom and industrial systems demanding comprehensive power integrity assurance.

Availability

MAX6728KAZWD3+T is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and battery-backed storage controllers requiring stable component supply, long-lifecycle support, and guaranteed lead-free compliance.

Supply support for MAX6728KAZWD3+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, mixed-signal, and power-management ICs for demanding industrial, automotive, and communications applications.

The MAX6715–MAX6729 family delivers ultra-low-voltage, multi-rail supervision with integrated watchdog and power-fail detection - engineered specifically for space-constrained, high-reliability systems where power integrity is mission-critical.

FAQ

What is the exact reset threshold voltage for VCC1 on the MAX6728KAZWD3+T?

The MAX6728KAZWD3+T has a factory-trimmed VCC1 reset threshold of 1.620V (typical), with tolerance of ±45mV (1.575V to 1.665V) over temperature. This value is encoded by the 'Z' suffix in the part number and is guaranteed across the -40°C to +85°C operating range per the datasheet's Electrical Characteristics table.

Does the MAX6728KAZWD3+T support monitoring a negative supply voltage?

Yes - the MAX6728KAZWD3+T can monitor negative supplies using the PFI input with an appropriate resistor-divider network as shown in Figure 3b of the datasheet. When the negative supply drops, PFO transitions high, providing an interrupt or reset trigger. Accuracy depends on PFI threshold tolerance (±15.5mV), resistor matching, and VCC stability.

What is the function of Pin 4 (PFO) on the MAX6728KAZWD3+T?

Pin 4 is the active-low open-drain power-fail output (PFO). It asserts low when the voltage at PFI falls below 626.5mV. Unlike the RST output, PFO deasserts immediately when PFI rises above threshold - with no timeout delay - making it ideal for real-time power-fail warnings and fast-response system actions in the MAX6728KAZWD3+T.

How does the watchdog timer behave after power-up in the MAX6728KAZWD3+T?

After power-up or any reset event, the MAX6728KAZWD3+T enters a 35s minimum startup watchdog mode. The 1.12s normal timeout period begins only after the first valid edge (rising or falling) is detected on WDI. This prevents spurious resets during boot sequences while ensuring rapid fault detection once software is running - a key behavior of the MAX6728KAZWD3+T.

Can the MAX6728KAZWD3+T operate with VCC1 below 1.8V?

Yes - the MAX6728KAZWD3+T is guaranteed to assert valid reset states as long as either VCC1 or VCC2 remains ≥ 0.8V. While VCC1 nominal range is 1.8V–5.0V, the device functions correctly down to 0.8V on VCC1, enabling use in ultra-low-voltage applications such as energy-harvesting systems where the MAX6728KAZWD3+T maintains supervision integrity during deep brownout.