Analog Devices Inc./Maxim Integrated MAX6729KAVDD3+T

Overview

MAX6729KAVDD3+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 externally adjustable RSTIN input (626.5mV reference) with push-pull active-low reset output, power-fail input/output, and watchdog timer. It guarantees valid reset assertion down to VCC1 or VCC2 = 0.8V and supports industrial temperature range (–40°C to +85°C).

For engineers reviewing the MAX6729KAVDD3+T datasheet, MAX6729KAVDD3+T pinout, MAX6729KAVDD3+T application, or MAX6729KAVDD3+T equivalent, key selection criteria include triple-supply monitoring capability, 210ms (min) reset timeout, push-pull RST/PFO outputs referenced to VCC1, integrated power-fail comparator with 2µs delay, and 14µA typical supply current at 3.6V.

Technical Context

The MAX6729KAVDD3+T implements independent dual-threshold voltage monitoring for primary (VCC1) and secondary (VCC2) supplies, plus a high-impedance RSTIN input for third-voltage supervision using an internal 626.5mV reference. Its power-fail comparator (PFI/PFO) operates with 3mV hysteresis and 2µs propagation delay, while the watchdog timer provides dual-mode timing: 35s (min) startup period followed by 1.12s (min) normal timeout after first WDI transition.

Reset assertion is guaranteed when either VCC1 or VCC2 exceeds 0.8V, and the push-pull RST and PFO outputs are referenced to VCC1. The device uses BiCMOS process (1072 transistors), achieves ±0.5% reset threshold hysteresis, and maintains immunity to VCC transients ≤20µs at 100mV overdrive.

Key Specifications

Pinout & Package

MAX6729KAVDD3+T is housed in an 8-pin SOT23-8 package (2.0mm × 2.1mm × 1.25mm), lead-free, RoHS-compliant, 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 MAX6729KAVDD3+T, MAX6728KA+T offers identical supervision functionality but requires external pullup for PFO, while TPS3808G33DBVR reduces BOM count in simpler dual-rail systems but omits RSTIN and PFI - making MAX6729KAVDD3+T the only option supporting three independent supply checks with integrated power-fail alerting.

Availability

MAX6729KAVDD3+T is available at Aetrix Electronics and suitable for industrial PLC controllers, network router power management, battery-powered medical sensors, and automotive infotainment head units requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for MAX6729KAVDD3+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 multivoltage embedded systems requiring compact, ultra-low-power supervision with flexible reset timing and auxiliary monitoring capabilities - targeting space-constrained, battery-aware, and mission-critical applications.

FAQ

What is the exact reset threshold voltage for VCC1 on MAX6729KAVDD3+T?

The MAX6729KAVDD3+T has a factory-trimmed VCC1 reset threshold of 4.625V (falling edge), with ±125mV tolerance over temperature and supply variations. This value is encoded in the "K" suffix per Maxim's Reset Voltage Threshold Suffix Guide and is verified across –40°C to +85°C. The threshold remains stable with 20ppm/°C tempco, ensuring consistent brownout detection in industrial environments.

Does MAX6729KAVDD3+T support monitoring a 1.2V core supply as the third voltage?

Yes, MAX6729KAVDD3+T supports monitoring a 1.2V core supply via its RSTIN pin using an external resistor divider. With a 626.5mV internal reference, a standard R1/R2 network (e.g., R1 = 110kΩ, R2 = 130kΩ) scales 1.2V down to ~626mV at RSTIN. The 25nA max input current ensures minimal loading, preserving accuracy even with high-value resistors for ultra-low power consumption.

How does the power-fail function work on MAX6729KAVDD3+T?

The MAX6729KAVDD3+T uses its PFI pin as a high-impedance input to a comparator with 626.5mV threshold and 3mV hysteresis. When PFI voltage drops below threshold, PFO asserts low within 2µs - immediately signaling power degradation without reset timeout delay. PFO is push-pull and referenced to VCC1, enabling direct connection to µP interrupt pins without external components.

What is the watchdog timeout behavior after power-on for MAX6729KAVDD3+T?

Upon power-on or reset assertion, MAX6729KAVDD3+T enters a 35s (minimum) long-startup watchdog mode, allowing complex boot sequences to complete. After the first valid WDI edge (rising or falling), it switches to 1.12s (minimum) normal timeout mode. If WDI remains static beyond that period, MAX6729KAVDD3+T asserts RST for 210ms - ensuring rapid recovery from software hangs post-initialization.

Can MAX6729KAVDD3+T operate reliably when VCC1 drops to 0.9V?

Yes, MAX6729KAVDD3+T guarantees correct reset output logic state down to VCC1 = 0.8V or VCC2 = 0.8V. At 0.9V, both push-pull RST and PFO outputs maintain valid logic levels: VOL ≤ 0.4V at ISINK = 3.2mA and VOH ≥ 0.8 × VCC1 at ISOURCE = 800µA. This ensures interoperability with low-voltage µPs during brownout recovery without external level-shifting.