Analog Devices Inc./Maxim Integrated MAX6340UK28-T

Overview

MAX6340UK28-T 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 supply voltage in battery-powered embedded controllers and portable medical instruments.

For engineers reviewing the MAX6340UK28-T datasheet, MAX6340UK28-T pinout, MAX6340UK28-T application, or MAX6340UK28-T equivalent, key selection criteria include its SOT23-5 open-drain output architecture, 1.6µA typical quiescent current, ±2.5% reset threshold accuracy over temperature, and compatibility with external pullup voltages up to 5.5V.

Technical Context

The MAX6340UK28-T implements a precision bandgap-based voltage detector with 0.65V internal ramp reference and 240nA constant-current source charging the external SRT capacitor. Reset assertion occurs when VCC falls below 2.8V; deassertion requires both VCC rise above threshold and SRT capacitor voltage ramp to 0.65V.

Its open-drain RESET output supports wired-OR configurations and logic-level translation across supplies from 0V to 5.5V. Immunity to short VCC transients (e.g., ≤50µs for 100mV overdrive) is achieved via internal timing hysteresis and transient filtering on the VCC detection path.

Key Specifications

Pinout & Package

MAX6340UK28-T is housed in a 5-pin SOT23-5 package with 1.6mm × 2.9mm footprint and 0.95mm height, optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3470ASX-2.83V and NCP302LSN28T1G, the MAX6340UK28-T uniquely combines pin-compatible SOT23-5 packaging, open-drain output, and capacitor-programmable timeout-enabling design flexibility without PCB revision or additional components.

Availability

MAX6340UK28-T is available at Aetrix Electronics and suitable for battery-powered medical monitors, automotive body control modules, industrial IoT sensor nodes, and portable test equipment requiring stable component supply across extended temperature ranges.

Supply support for MAX6340UK28-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, designs precision analog and mixed-signal ICs for industrial, automotive, communications, and computing markets.

The MAX6340 series belongs to Maxim's microprocessor supervisory circuits product line, engineered specifically for low-power, high-accuracy reset generation in space- and energy-constrained embedded systems.

FAQ

What is the exact reset threshold voltage of the MAX6340UK28-T and how tightly is it specified?

The MAX6340UK28-T has a factory-laser-trimmed nominal reset threshold of 2.80V, with guaranteed accuracy of ±2.5% 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" with VTH = 2.80V and tolerance bounds of VTH ± 2.5%. The suffix "28" in the part number explicitly denotes the 2.8V threshold variant per Table 1 in the datasheet.

How does the capacitor-adjustable reset timeout work on the MAX6340UK28-T, and what is the minimum achievable timeout?

The MAX6340UK28-T uses an internal 240nA current source to charge an external capacitor (CSRT) connected between the SRT pin and ground. Reset deassertion occurs when the capacitor voltage reaches 0.65V, yielding tRP = (0.65V / 240nA) + 275µs = 2.73×10⁶×CSRT + 275µs. With CSRT = 0 (shorted), the minimum timeout is 275µs - a fixed base delay independent of capacitor tolerance or temperature drift.

Why does the MAX6340UK28-T use an open-drain RESET output instead of push-pull, and what pullup resistor value is recommended?

The open-drain RESET output on the MAX6340UK28-T enables wired-OR functionality and voltage-level translation, allowing the same reset signal to interface with µPs operating at different supply voltages (0V to 5.5V). A pullup resistor between 10kΩ and 100kΩ is recommended: values ≥10kΩ ensure adequate noise margin when RESET is asserted (low), while ≤100kΩ guarantee sufficient drive strength to overcome input leakage and parasitic capacitance when RESET is deasserted (high).

Can the MAX6340UK28-T operate reliably when the supply voltage VCC drops below 1.6V, and what is its guaranteed functional limit?

Yes - the MAX6340UK28-T is explicitly guaranteed to provide valid reset assertion and deassertion down to VCC = 1.0V, as stated in the "Guaranteed Reset Valid to VCC = 1V" feature and confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables. Below 1.0V, RESET output drive capability degrades; however, for applications requiring validity down to 0V, an external 100kΩ pulldown resistor on the RESET line is recommended per the Applications Information section.

Is the MAX6340UK28-T pin-compatible with other members of the MAX6340/MAX6421–MAX6426 family, and which specific variants share the same SOT23-5 footprint?

Yes - the MAX6340UK28-T shares identical 5-pin SOT23-5 pinout and footprint with MAX6424UKxx-T, MAX6425UKxx-T, and MAX6426UKxx-T variants. All these parts have the same pin assignments: Pin 1 = GND, Pin 2 = N.C., Pin 3 = SRT, Pin 4 = VCC, Pin 5 = RESET. This allows direct substitution within the same package family when adjusting reset threshold or output type (e.g., replacing MAX6340UK28-T with MAX6425UK28-T for identical specs but different top-mark code).