Analog Devices Inc./Maxim Integrated MAX6425UK21+T

Overview

MAX6425UK21+T from Analog Devices is a low-power microprocessor supervisor IC with open-drain active-low reset output, 2.100V ±2.5% factory-trimmed reset threshold, capacitor-adjustable reset timeout (2.73×10⁶ × CSRT + 275µs), and guaranteed operation down to VCC = 1V. It monitors supply voltage in portable battery-powered systems and asserts reset during brownout or power-down events.

For engineers reviewing the MAX6425UK21+T datasheet, MAX6425UK21+T pinout, MAX6425UK21+T application, or MAX6425UK21+T equivalent, key selection criteria include its 5-pin SOT23-5 open-drain output architecture, 1.6µA typical quiescent current, -40°C to +125°C operating range, and compatibility with multi-rail logic interfacing via external pullup.

Technical Context

The MAX6425UK21+T implements a precision voltage detector with laser-trimmed internal reference and 240nA SRT ramp current source. Reset assertion is triggered when VCC falls below 2.100V, with hysteresis of 4×VTH (8.4mV) and immunity to transients ≤50µs at 100mV overdrive.

Its reset timeout is set externally via capacitor CSRT connected between SRT and GND, enabling programmable delay from 275µs (CSRT = 0) up to 5.75ms (CSRT = 1500pF). The open-drain RESET output supports logic-level translation across supplies from 0V to 5.5V using an external pullup resistor (10kΩ–100kΩ).

Key Specifications

Pinout & Package

MAX6425UK21+T is housed in a 5-pin SOT23-5 package with exposed pad (RoHS-compliant lead-free). Pin 1 is SRT (Set Reset Timeout), Pin 2 is GND, Pin 3 is N.C., Pin 4 is VCC, and Pin 5 is RESET (open-drain active-low).

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP302LSN21T1G and TLV809EC21DBZR, the MAX6425UK21+T uniquely delivers capacitor-programmable reset timeout in a 5-pin SOT23-5 open-drain package, enabling precise timing alignment with diverse µP requirements without layout changes.

Availability

MAX6425UK21+T is available at Aetrix Electronics and suitable for battery-powered medical sensors, automotive body control modules, and industrial IoT edge nodes requiring stable component supply and long-term lifecycle support.

Supply support for MAX6425UK21+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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The MAX6425UK21+T belongs to the MAX6340/MAX6421–MAX6426 family of low-power µP supervisors designed specifically for reliable power-monitoring in space-constrained, battery-sensitive, and wide-temperature embedded systems.

FAQ

What is the exact reset threshold voltage of the MAX6425UK21+T and how does it vary with temperature?

The MAX6425UK21+T has a nominal reset threshold of 2.100V, with ±1.5% accuracy at +25°C and ±2.5% over the full -40°C to +125°C operating range. This tolerance is achieved via laser trimming and ensures consistent brownout detection across automotive and industrial environments without external calibration. The MAX6425UK21+T maintains this specification under all specified supply and load conditions.

Can the MAX6425UK21+T be used with a 1.8V microcontroller reset input?

Yes, the MAX6425UK21+T's open-drain RESET output is fully compatible with 1.8V logic. Connect a 10kΩ–100kΩ pullup resistor from the RESET pin to the 1.8V supply rail. When asserted, the output sinks current to ground (VOL ≤ 0.3V at ISINK = 500µA), ensuring a solid logic low; when deasserted, the pullup establishes a valid 1.8V logic high. This eliminates level-shifter components in the MAX6425UK21+T design.

How do I calculate the SRT capacitor value needed for a 4.0ms reset timeout with the MAX6425UK21+T?

Use the formula CSRT = (tRP − 275µs) / 2.735×10⁶, where tRP = 4.0ms = 0.004s. Substituting gives CSRT = (0.004 − 0.000275) / 2,735,000 ≈ 1362pF. A standard 1300pF or 1500pF ceramic capacitor yields 3.88ms or 4.375ms timeout respectively. The MAX6425UK21+T datasheet confirms 1500pF produces 4.375ms typical timeout at +25°C.

Does the MAX6425UK21+T require any external components besides the SRT capacitor?

Yes - the MAX6425UK21+T requires an external pullup resistor on the RESET pin (10kΩ–100kΩ to target logic rail) and the SRT timing capacitor (low-leakage ceramic recommended). No other passive components are needed. The N.C. pin (Pin 3) may be left unconnected or tied to GND; it serves no functional purpose in the MAX6425UK21+T circuit.

Is the MAX6425UK21+T AEC-Q100 qualified for automotive applications?

No - the MAX6425UK21+T is not AEC-Q100 qualified. Only the MAX6340UK31/V+T variant in this family carries AEC-Q100 Grade 1 (-40°C to +125°C) qualification. The MAX6425UK21+T shares the same -40°C to +125°C operating range and robust transient immunity but lacks formal automotive qualification documentation and test reporting required for AEC-Q100 compliance.