Analog Devices Inc./Maxim Integrated MAX6425UK28

Overview

MAX6425UK28 from Maxim Integrated is a low-power microprocessor reset supervisor IC with open-drain active-low RESET output, 2.8V factory-trimmed reset threshold (±2.5% over -40°C to +125°C), capacitor-adjustable reset timeout (275µs base + 2.73s/F × CSRT), and guaranteed operation down to VCC = 1V. It monitors system supply voltage in portable, battery-powered, and automotive electronics to prevent code-execution errors during power-up, brownout, or power-down.

For engineers reviewing the MAX6425UK28 datasheet, MAX6425UK28 pinout, MAX6425UK28 application, or MAX6425UK28 equivalent, key selection criteria include its SOT23-5 open-drain output compatibility with mixed-voltage µP interfaces, 1.6µA typical quiescent current at +25°C, ±2.5% reset threshold accuracy across temperature, and immunity to sub-50µs VCC transients when overdriven by 100mV.

Technical Context

The MAX6425UK28 implements a precision voltage detector with laser-trimmed internal reference and hysteresis (4×VTH), coupled to a 240nA constant-current ramp generator that charges an external capacitor (CSRT) connected to the SRT pin. Reset assertion occurs when VCC falls below 2.8V; deassertion requires both VCC > 2.8V and the SRT capacitor voltage ramping to 0.65V.

Its open-drain RESET output supports wired-OR configuration and logic-level translation via external pullup (10kΩ–100kΩ) to any supply from 0V to 5.5V. The device guarantees valid RESET output down to VCC = 1V, with VOL ≤ 0.3V at ISINK = 1.2mA (VCC ≥ 2.7V) and ILKG ≤ 1.0µA when reset is not asserted.

Key Specifications

Pinout & Package

MAX6425UK28 is housed in a 5-pin SOT23-5 package (outline 21-0057), with 1.3mm × 2.9mm footprint and 0.95mm height. Pin 1 is marked with a dot; pin numbering follows standard SOT23 convention (counterclockwise from mark).

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP302HS28T1G and TLV809E28DBZR, the MAX6425UK28 uniquely combines factory-trimmed 2.8V threshold, user-adjustable timeout via SRT capacitor, and open-drain output - enabling design reuse across multiple µP platforms without layout changes.

Availability

MAX6425UK28 is available at Aetrix Electronics and suitable for portable medical sensors, battery-powered telematics units, and automotive body control modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for MAX6425UK28 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 demanding industrial, automotive, and computing applications, with emphasis on power efficiency and reliability.

The MAX6421–MAX6426 family delivers low-power, capacitor-programmable reset supervision for battery-constrained and safety-critical systems - targeting applications where deterministic reset timing and wide-VCC operability are essential.

FAQ

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

The MAX6425UK28 features a factory-trimmed reset threshold of 2.80V, with guaranteed accuracy of ±2.5% over the full operating temperature range (-40°C to +125°C). This specification is confirmed in Table 1 of the datasheet (suffix "28") and Electrical Characteristics section, where VTH min/max values are listed as 2.730V/2.870V at TA = -40°C to +125°C. The MAX6425UK28 uses laser-trimmed resistors to achieve this precision without external calibration.

How do I calculate the external capacitor value needed for a 150ms reset timeout with MAX6425UK28?

Use the formula tRP = 2.73 × 10⁶ × CSRT + 275µs, where tRP is in seconds and CSRT in farads. For tRP = 0.150s: CSRT = (0.150 − 0.000275) / 2.73 × 10⁶ = 54.3nF. A standard 56nF ceramic capacitor (low-leakage, X7R or C0G) yields ~156ms timeout. The MAX6425UK28's 240nA SRT ramp current and 0.65V internal reference enable this predictable linear relationship.

Can MAX6425UK28 drive a 3.3V microcontroller reset input directly, and what pullup resistor value is recommended?

Yes - the MAX6425UK28's open-drain RESET output is compatible with 3.3V µP reset inputs. Connect a 10kΩ to 100kΩ pullup resistor from RESET to the 3.3V supply. At ISINK = 1.2mA (VCC ≥ 2.7V), VOL ≤ 0.3V ensures solid logic-low assertion; at high state, the pullup establishes a clean 3.3V logic-high. This eliminates level-shifter ICs and simplifies interface design for the MAX6425UK28.

Does MAX6425UK28 remain functional during severe brownout conditions where VCC drops below 2.0V?

Yes - the MAX6425UK28 guarantees valid RESET output operation down to VCC = 1.0V, as specified in Absolute Maximum Ratings and Electrical Characteristics. Its internal circuitry continues asserting RESET until VCC rises above 2.8V and the SRT capacitor ramps to 0.65V. Below 1.0V, RESET behavior is undefined, but the MAX6425UK28 maintains correct state through the critical 1.0V–2.8V brownout window.

Is MAX6425UK28 pin-compatible with other devices in the MAX642x family, and which ones share the same SOT23-5 footprint?

Yes - MAX6425UK28 shares identical 5-pin SOT23-5 pinout and footprint with MAX6340, MAX6424, and MAX6426. All route VCC to pin 4, GND to pin 2, SRT to pin 1, RESET to pin 5, and N.C. to pin 3. This enables drop-in replacement within the same package group when changing reset threshold (e.g., UK29 → UK28) or output type (e.g., MAX6424 push-pull → MAX6425 open-drain), provided system-level timing and interface requirements align.