Analog Devices Inc./Maxim Integrated MAX6425UK27

Overview

MAX6425UK27 from Maxim Integrated is a low-power microprocessor supervisor IC that monitors VCC supply voltage and asserts an active-low open-drain RESET signal when voltage falls below 2.700V (±2.5% over temperature). It features capacitor-adjustable reset timeout (275µs base + 2.73s/F × CSRT), guaranteed operation down to VCC = 1V, and consumes only 1.6µA typical quiescent current. It is used in battery-powered controllers and portable equipment for reliable power-on reset and brownout protection.

For engineers reviewing the MAX6425UK27 datasheet, MAX6425UK27 pinout, MAX6425UK27 application, or MAX6425UK27 equivalent, key selection criteria include its 2.7V reset threshold accuracy, SOT23-5 open-drain output architecture, capacitor-programmable timeout, immunity to short VCC transients, and compatibility with multi-rail logic interfaces via external pullup.

Technical Context

The MAX6425UK27 implements a precision bandgap-based voltage detector with laser-trimmed resistors to set its 2.700V reset threshold (±2.5% over −40°C to +125°C). Its reset assertion is triggered by VCC falling below VTH, and deassertion is delayed by a ramp-controlled timer using an internal 240nA current source charging an external capacitor (CSRT) to a 0.65V reference.

As an open-drain supervisor, MAX6425UK27 requires an external pullup resistor (10kΩ–100kΩ) to a logic rail up to 5.5V, enabling wired-OR reset configurations and voltage-level translation across mixed-supply systems. Its RESET output remains valid down to VCC = 1V but is not specified for operation at VCC < 1V.

Key Specifications

Pinout & Package

MAX6425UK27 is housed in a 5-pin SOT23-5 package (2.9mm × 1.6mm × 1.1mm), RoHS-compliant and available in leaded or lead-free variants. Pin 1 is SRT (Set Reset Timeout), Pin 2 is GND, Pin 3 is N.C. (not internally connected), Pin 4 is VCC, and Pin 5 is RESET (open-drain active-low output).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6425UK27, NCP302LSN27T1G offers lower cost but sacrifices timeout adjustability and open-drain versatility, while TLV803EB27DBZR matches the open-drain interface but trades off quiescent current efficiency and transient robustness-making MAX6425UK27 optimal for designs requiring field-tunable reset timing and multi-rail interoperability.

Availability

MAX6425UK27 is available at Aetrix Electronics and suitable for battery-powered controllers, portable medical devices, and automotive body electronics requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6425UK27 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 and mixed-signal ICs for power, sensing, and interface applications in industrial, automotive, and computing markets.

The MAX6421–MAX6426 family was engineered specifically for low-power, capacitor-programmable microprocessor supervision in space- and energy-constrained systems-emphasizing accuracy, flexibility, and robustness over wide temperature and voltage ranges.

FAQ

What is the exact reset threshold voltage of the MAX6425UK27 and how tightly is it specified?

The MAX6425UK27 has a nominal reset threshold of 2.700V, factory-trimmed and specified with ±2.5% accuracy over the full operating temperature range of −40°C to +125°C. This tolerance is confirmed in the Electrical Characteristics table under "VCC Reset Threshold Accuracy" and applies across all VCC supply levels from 1.0V to 5.5V. The suffix "27" in MAX6425UK27 directly denotes this 2.700V threshold per Table 1 in the datasheet.

Does the MAX6425UK27 require an external pullup resistor on its RESET pin, and if so, what value range is recommended?

Yes, the MAX6425UK27 features an open-drain RESET output and requires an external pullup resistor. A value between 10kΩ and 100kΩ is recommended, selected based on bus capacitance, rise-time requirements, and sink current of connected loads. For example, a 47kΩ resistor provides adequate noise margin and fast enough rise time for most µP reset inputs while minimizing static current draw from the pullup rail.

How is the reset timeout period calculated for the MAX6425UK27, and what capacitor value yields a 100ms delay?

The reset timeout period for MAX6425UK27 is calculated as tRP = (2.73 × 10⁶) × CSRT + 275µs, where tRP is in seconds and CSRT is in farads. To achieve a 100ms (0.1s) timeout: CSRT = (0.1 − 0.000275) / 2.73×10⁶ ≈ 36.4nF. A standard 36nF ceramic capacitor (low-leakage, X7R or C0G) meets this requirement and aligns with the Typical Operating Characteristics plot for CSRT vs. tRP.

Can the MAX6425UK27 operate reliably when the VCC supply drops below 1.0V, and what happens to the RESET output in that condition?

No-the MAX6425UK27 is only guaranteed to operate and maintain valid RESET output behavior down to VCC = 1.0V. Below this voltage, RESET output current-sinking capability declines drastically, and logic state becomes indeterminate. For applications requiring defined behavior near 0V, a 100kΩ pulldown resistor from RESET to GND can hold the line low, but this is a system-level design choice-not a feature supported by the MAX6425UK27 itself.

Is the MAX6425UK27 pin-compatible with other members of the MAX642x family, and which ones share identical pinout and function?

Yes, MAX6425UK27 is pin-compatible with MAX6340, MAX6424, and MAX6426-all offered in the same 5-pin SOT23-5 package with identical pin assignments (SRT, GND, N.C., VCC, RESET). However, output type differs: MAX6424 uses push-pull RESET, while MAX6340/MAX6425/MAX6426 use open-drain. Thus, direct substitution requires verifying output stage compatibility in the target circuit.