Analog Devices Inc./Maxim Integrated MAX6729KATED3+T

Overview

MAX6729KATED3+T 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 with 626mV internal reference. It provides push-pull active-low reset output, power-fail input/output (PFI/PFO), manual reset input (MR), and watchdog timer with 35s startup and 1.12s normal timeout - used in telecom power systems requiring reliable brownout detection and orderly shutdown.

For engineers reviewing the MAX6729KATED3+T datasheet, MAX6729KATED3+T pinout, MAX6729KATED3+T application, or MAX6729KATED3+T equivalent, key selection criteria include its triple-supply monitoring capability, guaranteed reset validity down to VCC1/VCC2 = 0.8V, push-pull RST output referenced to VCC1, PFO push-pull configuration, and 210ms (min) reset timeout period defined by the "D3" suffix.

Technical Context

The MAX6729KATED3+T implements dual independent voltage comparators for VCC1 and VCC2 plus a third high-impedance RSTIN comparator tied to a 626mV internal reference, enabling precise external resistor-divider-based monitoring of a third supply down to 0.62V. Its power-fail function uses a dedicated PFI input with 626.5mV threshold and 2µs propagation delay to PFO, supporting early warning and controlled shutdown.

This device integrates a dual-mode watchdog timer: after any reset event, it enforces a 35s minimum startup window before transitioning to 1.12s normal-mode timeout, ensuring robust boot sequence validation. All reset outputs are push-pull, referenced to VCC1 for RST and PFO, and internally pulled up MR input supports TTL/CMOS-compatible manual reset initiation.

Key Specifications

Pinout & Package

MAX6729KATED3+T is housed in an 8-pin SOT23-8 package (2.0mm × 2.1mm × 1.25mm), optimized for space-constrained PCB layouts in telecom and industrial modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6729KATED3+T, MAX6728KAED3+T offers identical supervision capability but requires external pullup on PFO, while TPS3808G33DBVR reduces cost and footprint at the expense of missing RSTIN, PFI, and dual-voltage flexibility - making MAX6729KATED3+T optimal for complex multirail systems needing integrated power-fail signaling.

Availability

MAX6729KATED3+T is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, server management controllers, and battery-powered edge gateways requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.

Supply support for MAX6729KATED3+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, triple-supply supervisory circuits targeting space- and power-constrained systems where reliability under brownout and power-fail conditions is critical.

FAQ

What is the exact reset timeout period for MAX6729KATED3+T?

The "D3" suffix in MAX6729KATED3+T specifies a minimum reset timeout period of 210ms. This is the guaranteed duration that the RST output remains asserted low after all monitored supplies (VCC1, VCC2, RSTIN) rise above their respective thresholds, or after MR returns high. The actual timeout may vary slightly with temperature and supply voltage but remains ≥210ms across the full -40°C to +85°C operating range.

Does MAX6729KATED3+T support monitoring a negative supply voltage?

Yes, MAX6729KATED3+T can monitor a negative supply using the PFI input with an appropriate resistor-divider network as shown in Figure 3b of the datasheet. When the negative supply is valid, PFO asserts low; as the supply degrades, PFO transitions high. Accuracy depends on PFI threshold tolerance (±15mV), resistor matching, and VCC stability - MAX6729KATED3+T itself does not require negative supply rails to operate.

What is the function of the WDI pin on MAX6729KATED3+T?

The WDI (Watchdog Input) pin on MAX6729KATED3+T monitors microprocessor activity: if WDI remains static (high or low) beyond the watchdog timeout period, it triggers a system reset. After each reset, MAX6729KATED3+T enters a 35s startup mode, then switches to 1.12s normal timeout. A rising or falling edge on WDI resets the timer - this allows firmware to "kick" the watchdog at strategic points in execution flow to prevent spurious resets.

Can MAX6729KATED3+T generate a reset if only VCC2 drops below threshold while VCC1 remains valid?

Yes, MAX6729KATED3+T asserts reset whenever either VCC1 or VCC2 falls below its factory-trimmed threshold - independently. With VCC1 = 4.625V threshold and VCC2 = 3.075V threshold, a drop in the 3.3V rail alone (e.g., to 3.0V) will cause RST to go low for the full 210ms timeout period, even if VCC1 remains at 5.0V. This dual-threshold independence ensures robust supervision of asymmetric power domains.

What are the absolute maximum ratings for VCC1 and VCC2 on MAX6729KATED3+T?

The absolute maximum rating for both VCC1 and VCC2 on MAX6729KATED3+T is -0.3V to +6.0V with respect to GND. Exceeding these limits may cause permanent damage. For reliable operation, VCC1 must be between 1.8V and 5.0V, and VCC2 between 0.9V and 3.3V per specification. The device guarantees correct reset logic state down to VCC1 or VCC2 = 0.8V, but operation below 0.8V is outside functional specifications.