Analog Devices Inc./Maxim Integrated MAX6725KAVDD3+

Overview

MAX6725KAVDD3+ from Maxim Integrated is a triple-voltage microprocessor supervisory circuit in an 8-pin SOT23 package, monitoring VCC1 (primary), VCC2 (secondary), and RSTIN (adjustable third supply) with factory-trimmed thresholds of 3.075V (VTH1), 2.925V (VTH2), and 626.5mV reference for RSTIN. It asserts active-low open-drain RST and RST2 outputs on fault, maintains reset for 210ms (min), and features manual reset input (MR), watchdog timer (1.12s normal / 35s startup timeout), and power-fail input/output (PFI/PFO). It ensures reliable reset assertion down to VCC1 or VCC2 = 0.8V in battery-powered embedded systems.

For engineers reviewing the MAX6725KAVDD3+ datasheet, MAX6725KAVDD3+ pinout, MAX6725KAVDD3+ application, or MAX6725KAVDD3+ equivalent, key selection criteria include dual open-drain reset outputs (RST/RST2), 3-supply monitoring capability with adjustable RSTIN threshold, guaranteed operation at 0.8V supply, 210ms reset timeout, and compatibility with low-power industrial and telecom power management designs.

Technical Context

The MAX6725KAVDD3+ integrates three independent voltage comparators: one for VCC1 (3.075V threshold), one for VCC2 (2.925V threshold), and one for RSTIN referenced to a 626.5mV internal bandgap. Reset assertion occurs if any monitored voltage falls below its threshold, MR is pulled low, or WDI fails to toggle within 1.12s (normal mode) after initial 35s startup window.

It provides two separate open-drain reset outputs-RST referenced to VCC1 and RST2 referenced to VCC2-enabling independent reset control of core and I/O domains. The PFI input monitors auxiliary supplies with 626.5mV threshold and drives PFO with 2µs propagation delay; both RSTIN and PFI exhibit ±25nA input current and 3mV hysteresis.

Key Specifications

Pinout & Package

MAX6725KAVDD3+ is housed in an 8-pin SOT23-8 package (2.0mm × 2.1mm × 1.25mm), optimized for space-constrained PCB layouts while maintaining thermal performance across -40°C to +85°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6725KAVDD3+, MAX6726KA+T offers push-pull drive convenience but sacrifices independent RST2 control, while TPS3808G33DBVR reduces cost and size at the expense of triple-supply flexibility and industrial-grade brownout immunity.

Availability

MAX6725KAVDD3+ is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, portable medical devices, and battery-powered set-top boxes requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for MAX6725KAVDD3+ 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, automotive, and communications markets.

The MAX6715–MAX6729 family was designed specifically for ultra-low-voltage, multirail microprocessor supervision in space- and power-constrained embedded systems, emphasizing reliability under brownout, noise immunity, and minimal external components.

FAQ

What is the exact reset threshold voltage for VCC1 on the MAX6725KAVDD3+?

The MAX6725KAVDD3+ has a factory-trimmed VCC1 reset threshold of 3.075V (typical), with tolerance of ±1.5% over temperature. This value is encoded in the "AV" suffix per Maxim's Reset Voltage Threshold Suffix Guide and is guaranteed across the full -40°C to +85°C operating range without external calibration.

Does the MAX6725KAVDD3+ support monitoring a third supply voltage, and how is it configured?

Yes, the MAX6725KAVDD3+ supports third-supply monitoring via the RSTIN pin, which compares the applied voltage against an internal 626.5mV reference. To monitor a higher voltage (e.g., 5V), use a resistor divider network where VEXT_TH = 626.5mV × ((R1 + R2)/R2); RSTIN must be left floating or tied to VCC1/VCC2 if unused.

What are the reset timeout options available for the MAX6725KAVDD3+, and how is the 210ms value selected?

The MAX6725KAVDD3+ uses the "D3" suffix to select a minimum reset timeout period of 210ms. This is one of five standard options (D1=1.1ms, D2=8.8ms, D3=140ms, D4=1120ms, D5=280ms, D6=560ms); D3 provides optimal hold time for mid-complexity processors without excessive boot delays.

How does the watchdog timer function differ between startup and normal operation in the MAX6725KAVDD3+?

The MAX6725KAVDD3+ watchdog features dual-mode timing: after any reset event (power-up, MR, or watchdog timeout), it enters a 35s (min) startup mode to accommodate lengthy firmware initialization. Once WDI receives its first valid edge, it switches to 1.12s (min) normal mode - resetting the µP if no further WDI transition occurs within that window.

Can the MAX6725KAVDD3+ operate reliably when VCC1 drops below 1.0V, and what design considerations apply?

Yes, the MAX6725KAVDD3+ guarantees valid reset output logic states down to VCC1 or VCC2 = 0.8V. For operation near this limit, ensure RST and RST2 are open-drain with appropriately sized pull-up resistors (e.g., 100kΩ to respective rails) to maintain defined logic levels during deep brownout conditions.