Analog Devices Inc./Maxim Integrated MAX6729KAVHD3+

Overview

MAX6729KAVHD3+ 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 supply via RSTIN (626.5mV reference). It provides push-pull active-low reset output, power-fail input/output (PFI/PFO), manual reset (MR), and watchdog timer (35s startup / 1.12s normal timeout), designed for reliable system initialization and brownout protection in multivoltage embedded systems.

For engineers reviewing the MAX6729KAVHD3+ datasheet, MAX6729KAVHD3+ pinout, MAX6729KAVHD3+ application, or MAX6729KAVHD3+ equivalent, key selection criteria include its triple-supply monitoring capability with factory-trimmed thresholds, guaranteed reset validity down to VCC1 or VCC2 = 0.8V, push-pull RST output referenced to VCC1, PFO push-pull configuration, and 210ms (min) reset timeout period - all critical for telecom, industrial, and portable equipment requiring deterministic power sequencing and fault recovery.

Technical Context

The MAX6729KAVHD3+ integrates three independent voltage monitors: primary (VCC1), secondary (VCC2), and auxiliary (RSTIN/PFI), each with dedicated comparators and hysteresis (0.5% typical). Its dual-mode watchdog timer features a 35s minimum startup period for safe boot initialization and a 1.12s minimum normal timeout for runtime supervision, triggered by WDI edge transitions.

Reset assertion is synchronized across all monitored inputs (VCC1, VCC2, RSTIN, MR, WDI), with a fixed 210ms (min) timeout period after recovery. The PFI comparator drives a push-pull PFO output with 2µs propagation delay and 3mV hysteresis, enabling precise early power-fail detection without external components.

Key Specifications

Pinout & Package

MAX6729KAVHD3+ uses an 8-pin SOT23-8 package (2.0mm × 2.3mm × 1.0mm height), optimized for high-density PCB layouts in space-constrained applications such as portable electronics and telecom modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6729KAVHD3+, MAX6728KA+T offers identical triple-monitoring and timing but requires external PFO pullup, while TPS3808G33DBVR reduces functionality to dual monitoring only - making MAX6729KAVHD3+ the sole option supporting push-pull PFO, watchdog, and full triple-voltage supervision in one 8-pin SOT23.

Availability

MAX6729KAVHD3+ is available at Aetrix Electronics and suitable for telecom line cards, industrial PLC controllers, and portable medical monitors requiring stable component supply, guaranteed long-term availability, and compliance with RoHS and REACH standards.

Supply support for MAX6729KAVHD3+ 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-constrained systems - delivering integrated triple monitoring, watchdog, and power-fail functions in miniature SOT23 packages.

FAQ

What is the exact reset timeout period for MAX6729KAVHD3+?

The MAX6729KAVHD3+ has a minimum reset timeout period of 210ms, as indicated by the "D3" suffix in its part number. This value is guaranteed over the full -40°C to +85°C operating temperature range and ensures sufficient hold time for processor and peripheral initialization before release from reset. The actual timeout may vary slightly due to process and temperature, but remains ≥210ms under all specified conditions.

Does MAX6729KAVHD3+ support monitoring a 1.2V core supply?

Yes, MAX6729KAVHD3+ supports monitoring a 1.2V core supply using the RSTIN pin with an external resistor divider. With its 626.5mV internal reference voltage, a divider ratio of (1.2V / 0.6265V) ≈ 1.915 allows precise threshold setting - for example, R1 = 910kΩ and R2 = 1MΩ yields V_TH = 0.6265V × (1.91MΩ / 1MΩ) = 1.20V. Input leakage (<25nA) ensures minimal error from divider current.

How does the watchdog timer behave after power-up in MAX6729KAVHD3+?

After power-up or any reset event, MAX6729KAVHD3+ enters a 35s minimum startup watchdog mode. During this period, the WDI input must transition at least once to exit startup mode and enter the 1.12s minimum normal timeout mode. If no WDI edge occurs within 35s, the watchdog asserts reset. This architecture prevents false timeouts during lengthy system boot sequences while ensuring rapid fault detection during steady-state operation.

Can MAX6729KAVHD3+ monitor negative supply voltages?

Yes, MAX6729KAVHD3+ can monitor negative supplies using the PFI input with an appropriate resistor network, as shown in Figure 3b of the datasheet. When a negative rail (e.g., -12V) is applied through a divider to PFI, the internal 626.5mV reference enables detection of voltage decay toward zero. PFO asserts high when the negative supply magnitude drops below the programmed threshold, providing fail-safe signaling for bipolar power systems.

What is the maximum VCC transient duration that MAX6729KAVHD3+ can ignore without asserting reset?

MAX6729KAVHD3+ ignores negative-going VCC transients up to 20µs in duration when the overdrive is 100mV below the reset threshold, as characterized in the Typical Operating Characteristics graph (toc06). This immunity prevents spurious resets caused by switching noise or brief line disturbances. For deeper transients (e.g., 200mV overdrive), the allowable pulse width decreases proportionally - down to ~2µs - maintaining robust operation in electrically noisy environments.