Analog Devices Inc./Maxim Integrated MAX6340UK28

Overview

MAX6340UK28 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 period (275µs to >100ms) in a 5-pin SOT23-5 package. It monitors VCC from 1.0V to 5.5V, asserts reset below threshold, holds reset for timeout after VCC recovery, and operates down to VCC = 1V - used in battery-powered controllers and automotive ECUs for reliable power-on initialization.

For engineers reviewing the MAX6340UK28 datasheet, MAX6340UK28 pinout, MAX6340UK28 application, or MAX6340UK28 equivalent, key selection criteria include its open-drain logic compatibility with multiple supply rails, guaranteed reset validity at VCC ≥ 1V, capacitor-based timeout flexibility, and automotive-grade temperature range (–40°C to +125°C).

Technical Context

The MAX6340UK28 implements a precision voltage monitor with laser-trimmed internal reference and hysteresis (4 × VTH), coupled to a 240nA current source that charges an external capacitor on the SRT pin to generate the reset timeout delay. Its open-drain RESET output requires an external pullup and supports wired-OR configurations with auxiliary reset sources.

It uses BiCMOS process technology (295 transistors), features immunity to short VCC transients (<50µs for 100mV overdrive), and guarantees valid reset assertion/deassertion across –40°C to +125°C without requiring internal oscillator or watchdog functions.

Key Specifications

Pinout & Package

MAX6340UK28 is housed in a RoHS-compliant 5-pin SOT23-5 package (outline 21-0057, land pattern 90-0174), with 0.95mm pitch, 2.9mm × 1.6mm footprint, and thermal pad option not included. Pin 3 is internally unconnected (N.C.) and may be tied to GND.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3470ASX-28 and NCP302LSN28T1G, MAX6340UK28 provides superior threshold accuracy (±2.5% vs. ±3%), lower quiescent current (1.6µA vs. 1.8µA), and unique capacitor-adjustable timeout - enabling precise adaptation to diverse µP reset timing requirements without redesign.

Availability

MAX6340UK28 is available at Aetrix Electronics and suitable for battery-powered controllers, automotive engine control units, and portable medical devices requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6340UK28 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and computing markets.

The MAX6340 series belongs to Maxim's microprocessor supervisory product line, designed specifically for ultra-low-power, precision voltage monitoring and configurable reset timing in space-constrained, thermally demanding embedded systems.

FAQ

What is the exact reset threshold voltage of the MAX6340UK28?

The MAX6340UK28 has a factory-laser-trimmed reset threshold of 2.80V with ±2.5% accuracy over the full operating temperature range (–40°C to +125°C). This value is confirmed in Table 1 of the datasheet, where suffix "28" corresponds to nominal 2.8V, and electrical characteristics specify VTH = VTH ±2.5% at TA = –40°C to +125°C. The threshold is referenced to VCC and includes 4×VTH hysteresis.

Does the MAX6340UK28 require an external capacitor to function?

The MAX6340UK28 does not require an external capacitor to perform basic reset assertion - it will assert RESET whenever VCC falls below 2.8V. However, an external capacitor on the SRT pin is mandatory to enable the reset timeout delay function. Without CSRT, the reset timeout defaults to 275µs (minimum). To achieve longer delays (e.g., 50ms or 100ms), a capacitor (e.g., 18nF or 36nF) must be connected between SRT and GND per the formula tRP = 2.73×10⁶ × CSRT + 275µs.

Can the MAX6340UK28 drive a reset input directly without a pullup resistor?

No - the MAX6340UK28 features an open-drain RESET output and cannot drive a logic-high state actively. A pullup resistor (typically 10kΩ to 100kΩ) must be connected between the RESET pin and the target µP's logic supply rail (e.g., 3.3V or 5V). This ensures a defined high state when RESET is deasserted. The datasheet confirms this requirement in the Pin Description and Applications Information sections, noting that the output only sinks current when asserted.

Is the MAX6340UK28 qualified for automotive applications?

Yes - the MAX6340UK28 is rated for operation from –40°C to +125°C and is listed in the Ordering Information table with standard temperature grade covering that full range. While the specific part number MAX6340UK28-T does not carry the "/V" automotive qualification suffix (which denotes AEC-Q100 testing), its electrical specifications, packaging, and performance data (including transient immunity and thermal stability) align with automotive subsystem requirements. For AEC-Q100-certified use, the /V variant (e.g., MAX6340UK28/V+T) should be specified.

What is the maximum recommended value for the SRT capacitor in the MAX6340UK28?

The datasheet does not specify an absolute maximum CSRT value, but practical limits arise from leakage and board parasitics. Ceramic capacitors up to 15nF are validated in Typical Operating Characteristics (Figure toc02), showing stable timeout behavior. For timeouts beyond ~100ms, larger values (e.g., 22nF–47nF) may be used, provided low-leakage (<10nA) dielectric (e.g., C0G/NP0) is selected. Leakage currents degrade timing accuracy, so film or high-quality ceramic is preferred over electrolytic or Y5V types.