Analog Devices Inc./Maxim Integrated MAX6425UK28-T

Overview

MAX6425UK28-T from Maxim Integrated is a low-power microprocessor reset supervisor IC with open-drain active-low RESET output, 2.8V ±2.5% factory-trimmed reset threshold, and capacitor-adjustable reset timeout (275µs to >600ms). It monitors VCC from 1.0V to 5.5V, draws only 1.6µA typical supply current, and guarantees valid reset assertion down to VCC = 1V. It is used in battery-powered controllers and portable medical instruments requiring reliable power-on reset with flexible timing.

For engineers reviewing the MAX6425UK28-T datasheet, MAX6425UK28-T pinout, MAX6425UK28-T application, or MAX6425UK28-T equivalent, key selection criteria include its SOT23-5 open-drain output architecture, 2.8V threshold accuracy over -40°C to +125°C, capacitor-based timeout adjustability, guaranteed operation at VCC ≥ 1V, and immunity to sub-50µs VCC transients when overdriven by 100mV.

Technical Context

The MAX6425UK28-T implements a precision voltage detector with laser-trimmed internal reference and hysteresis of 4×VTH (≈11.2mV at 2.8V). Its reset timeout is generated by a 240nA constant-current source charging an external capacitor (CSRT) to a 0.65V ramp threshold, enabling accurate, temperature-stable delay setting independent of VCC.

As an open-drain supervisor, it requires an external pullup resistor (10kΩ–100kΩ) to any logic supply up to 5.5V, enabling level-shifting and wired-OR reset functionality. Its SRT pin is highly sensitive to stray capacitance and leakage, demanding short, isolated PCB traces for timing accuracy.

Key Specifications

Pinout & Package

MAX6425UK28-T is housed in a 5-pin SOT23-5 package (outline 21-0057), RoHS-compliant, with 0.95mm pitch and 2.9mm × 1.6mm footprint. Pin 1 is marked with a dot; pin order is standard SOT23 numbering (1–5 left-to-right).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6425UK28-T, NCP302HS28T1G offers smaller footprint but sacrifices timeout adjustability and open-drain versatility, while TPS3808G28DBVR provides similar open-drain capability but trades capacitor-based precision for resistor-set convenience and looser timing tolerance.

Availability

MAX6425UK28-T is available at Aetrix Electronics and suitable for battery-powered portable controllers, automotive body control modules, and portable medical monitoring devices requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.

Supply support for MAX6425UK28-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, automotive, and computing applications.

The MAX6421–MAX6426 family was designed specifically for ultra-low-power microprocessor supervision in space-constrained, battery-sensitive systems requiring precise, capacitor-tunable reset timing and robust glitch immunity.

FAQ

What is the exact reset threshold voltage of MAX6425UK28-T and how tightly is it specified?

The MAX6425UK28-T features a factory-laser-trimmed reset threshold of 2.80V, with guaranteed accuracy of ±2.5% (±70mV) over the full operating temperature range of -40°C to +125°C. This specification is confirmed in the Electrical Characteristics table under "VCC Reset Threshold Accuracy" and applies directly to the UK28-T variant per Table 1 suffix mapping.

Does MAX6425UK28-T support operation at VCC below 1.6V, and what is the minimum valid supply voltage?

Yes, MAX6425UK28-T guarantees functional reset assertion down to VCC = 1.0V, as explicitly stated in both the Absolute Maximum Ratings (supply voltage range: 1.0V to 5.5V) and the Detailed Description section. Below 1.0V, RESET output sinking capability degrades, but the device remains operational and valid above that threshold.

How is the reset timeout period calculated for MAX6425UK28-T, and what capacitor value yields a 200ms delay?

The reset timeout period tRP for MAX6425UK28-T is calculated as tRP = (2.73 × 10⁶) × CSRT + 275µs, where CSRT is in farads and tRP in seconds. To achieve 200ms (0.2s), solve: CSRT = (0.2 − 0.000275) / 2.73e6 ≈ 73.0nF. A standard 75nF ceramic capacitor yields ~207ms, well within typical tolerance.

Why does MAX6425UK28-T use an open-drain output instead of push-pull, and what pullup resistor is recommended?

MAX6425UK28-T uses an open-drain output to enable wired-OR reset architectures and level-shifting across different logic supplies (0–5.5V). A 10kΩ to 100kΩ pullup resistor is recommended - 47kΩ is typical - balancing low static power (≤100µA at 5V) with sufficient drive strength for CMOS inputs.

Is MAX6425UK28-T pin-compatible with any industry-standard alternatives, and which ones are documented in the datasheet?

Yes, the MAX6425UK28-T is explicitly documented as pin-compatible with NCP300–NCP303, MC33464/MC33465, S807/S808/S809, and RN5VD families in the datasheet's "Ordering Information" section. This compatibility applies to the 5-pin SOT23-5 package and identical pin functions (VCC, GND, N.C., SRT, RESET).