Analog Devices Inc./Maxim Integrated MAX6728KAYHD3+T

Overview

MAX6728KAYHD3+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 3.075V (VTH1), 2.925V (VTH2), and 626.5mV (VPFI); it provides open-drain active-low RST and PFO outputs, 210ms minimum reset timeout, and operates from -40°C to +85°C. It ensures reliable system reset during power-up, brownout, or power-fail events in multivoltage embedded systems.

For engineers reviewing the MAX6728KAYHD3+T datasheet, MAX6728KAYHD3+T pinout, MAX6728KAYHD3+T application, or MAX6728KAYHD3+T equivalent, key selection factors include its triple-supply monitoring capability, guaranteed reset validity down to VCC1/VCC2 = 0.8V, 14µA typical supply current at 3.6V, and integrated power-fail comparator with 2µs propagation delay - critical for orderly shutdown in telecom and industrial power management.

Technical Context

The MAX6728KAYHD3+T implements independent dual-threshold voltage comparators for VCC1 and VCC2, plus a dedicated high-impedance PFI input referenced to a 626.5mV internal bandgap reference. Its reset logic asserts RST low when any monitored supply falls below its threshold and holds RST low for a fixed 210ms (min) timeout after recovery.

It integrates a power-fail comparator with 3mV hysteresis and 2µs PFI-to-PFO delay, enabling early warning of supply degradation without requiring external timing components. The device guarantees valid reset output states even when VCC1 or VCC2 drops to 0.8V, supporting robust operation during deep brownout conditions.

Key Specifications

Pinout & Package

MAX6728KAYHD3+T is housed in an 8-pin SOT23 package (3.0mm × 1.6mm × 1.1mm body, 0.65mm pitch), optimized for space-constrained applications requiring triple-supply supervision with power-fail alerting.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6728KAYHD3+T, MAX6729KAHBD3+T offers push-pull drive for simplified interfacing but sacrifices open-drain flexibility, while TPS3808G33DBVR reduces feature set and current consumption but omits critical triple-monitoring and PFI capabilities required for comprehensive power integrity.

Availability

MAX6728KAYHD3+T is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, server management controllers, and medical imaging subsystems requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.

Supply support for MAX6728KAYHD3+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 demanding industrial, communications, and computing applications.

The MAX6715–MAX6729 family was designed specifically for multivoltage system supervision in space- and power-constrained environments, delivering integrated triple-monitoring, power-fail alerting, and ultra-low quiescent current in miniature SOT23 packages.

FAQ

What is the exact reset threshold voltage for VCC1 on the MAX6728KAYHD3+T?

The MAX6728KAYHD3+T has a factory-trimmed VCC1 reset threshold of 3.075V (typical), with a tolerance of ±1.5% over temperature. This value is confirmed in the Reset Voltage Threshold Suffix Guide where "Y" corresponds to 3.075V for VTH1, and is validated in the Electrical Characteristics table under VTH1 parameter with MIN/TYP/MAX values of 3.000V/3.075V/3.150V.

Does the MAX6728KAYHD3+T support monitoring a negative supply voltage?

Yes, the MAX6728KAYHD3+T can monitor a negative supply using the PFI input with an appropriate resistor-divider configuration as shown in Figure 3b of the datasheet. When the negative supply is valid, PFO asserts low; as the supply degrades, PFO deasserts. Accuracy depends on PFI threshold tolerance (±15mV), resistor matching, and VCC stability - no internal polarity inversion is required.

What is the function of Pin 8 (NC) on the MAX6728KAYHD3+T?

Pin 8 on the MAX6728KAYHD3+T is a no-connect (NC) terminal - it is internally unconnected and serves no electrical function. Per Maxim's layout guidance, it should be left floating or tied to GND for mechanical stability and EMI reduction; connecting it to any active signal may cause unpredictable behavior or damage.

How does the power-fail comparator in the MAX6728KAYHD3+T differ from the main reset comparators?

The MAX6728KAYHD3+T power-fail comparator operates independently of the reset timeout timer: PFO asserts immediately (2µs delay) when PFI falls below 626.5mV and deasserts instantly upon recovery - no timeout is applied. In contrast, RST remains asserted for the full 210ms timeout period after VCC1/VCC2/PFI recovery, ensuring processor initialization completes before release.

Can the MAX6728KAYHD3+T be used without connecting the MR pin?

Yes, the MR pin on the MAX6728KAYHD3+T has an internal 50kΩ pullup resistor to VCC1 and may be left unconnected if manual reset functionality is not required. Leaving MR floating ensures it remains at logic-high, preventing unintended reset assertion; no external components are needed unless noise immunity is required (e.g., 0.1µF capacitor to GND in high-noise environments).