Analog Devices Inc./Maxim Integrated MAX6340UK28+

Overview

MAX6340UK28+ from Maxim Integrated is a low-power, open-drain microprocessor reset supervisor IC designed for precise VCC monitoring and capacitor-adjustable reset timeout in space-constrained systems. It monitors supply voltages from 1.6V to 5V with a factory-trimmed 2.800V reset threshold (±2.5% over –40°C to +125°C), asserts an active-low open-drain RESET signal during brownout, and guarantees valid operation down to VCC = 1V - used in battery-powered controllers and automotive ECUs requiring reliable power-on reset sequencing.

For engineers reviewing the MAX6340UK28+ datasheet, MAX6340UK28+ pinout, MAX6340UK28+ application, or MAX6340UK28+ equivalent, key selection criteria include its SOT23-5 open-drain output architecture, 1.6µA typical quiescent current, capacitor-programmable reset timeout (275µs base + 2.73×10⁶ × CSRT), ±2.5% reset threshold accuracy over temperature, and guaranteed operation at VCC ≥ 1V - critical for ultra-low-power embedded reset integrity.

Technical Context

The MAX6340UK28+ implements a precision voltage comparator with laser-trimmed internal reference and hysteresis (4×VTH) to reject short VCC transients. Its reset timeout is generated by a 240nA constant-current source charging an external capacitor (CSRT) to a 0.65V ramp threshold, enabling accurate, user-defined delay from 275µs to >100ms.

As an open-drain device, it requires an external pullup resistor (10kΩ–100kΩ) to any logic supply up to 5.5V, supporting mixed-voltage system interfacing and wired-OR reset architectures. The SRT pin is highly sensitive to leakage and stray capacitance, demanding careful PCB layout with short, isolated traces.

Key Specifications

Pinout & Package

MAX6340UK28+ is housed in a RoHS-compliant 5-pin SOT23-5 package (outline 21-0057), measuring 2.9mm × 1.6mm × 1.1mm, with gull-wing leads and thermal pad not connected internally.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3470ASX-28 and NCP302LSN28T1G, the MAX6340UK28+ uniquely combines capacitor-adjustable timeout, 1.0V minimum VCC operation, and ±2.5% threshold accuracy over full automotive temperature range - making it the only option for designs needing both timing flexibility and deep-brownout robustness.

Availability

MAX6340UK28+ is available at Aetrix Electronics and suitable for battery-powered controllers, automotive engine control units, and portable industrial sensors 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 semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The MAX6340 series belongs to Maxim's precision voltage supervisor product line, engineered for ultra-low-power, high-accuracy reset generation in harsh environments where supply stability cannot be assumed.

FAQ

What is the exact reset threshold voltage of the MAX6340UK28+?

The MAX6340UK28+ features a factory-trimmed nominal reset threshold of 2.800V, with guaranteed tolerance of ±2.5% over the full operating temperature range of –40°C to +125°C. This value is laser-trimmed during production and confirmed in the Electrical Characteristics table of the datasheet; it applies specifically to the "28" suffix variant and is not adjustable post-manufacture.

Does the MAX6340UK28+ require an external pullup resistor on the RESET pin?

Yes, the MAX6340UK28+ has an open-drain RESET output and requires an external pullup resistor to establish a defined logic-high level. A 10kΩ to 100kΩ resistor to any supply between 0V and 5.5V is recommended. The value must balance leakage current sinking (to ensure solid low) and rise time (to meet µP setup requirements); 47kΩ is commonly used for 3.3V systems.

How is the reset timeout period set for the MAX6340UK28+?

The reset timeout period for the MAX6340UK28+ is set by connecting an external capacitor (CSRT) between the SRT pin and ground. The relationship is tRP = (2.73 × 10⁶) × CSRT + 275µs, where tRP is in seconds and CSRT is in farads. For example, a 1500pF capacitor yields ~4.375ms timeout. CSRT must be low-leakage ceramic (≤10nA) to maintain accuracy.

Can the MAX6340UK28+ operate reliably when VCC drops below 1.5V?

Yes - the MAX6340UK28+ guarantees valid RESET assertion and deassertion down to VCC = 1.0V, as confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables. Below 1.0V, output drive capability degrades, but the device continues to monitor and respond to threshold crossing until VCC reaches ~0.8V. This makes MAX6340UK28+ suitable for deep brownout detection where other supervisors fail.

Is the MAX6340UK28+ pin-compatible with other members of the MAX642x family?

No - the MAX6340UK28+ uses a 5-pin SOT23-5 package with pinout {SRT, GND, N.C., VCC, RESET}, whereas MAX6421/MAX6422/MAX6423 use 4-pin SC70 or SOT143 packages. However, MAX6340UK28+ is explicitly stated in the datasheet to be pin-compatible with the LP3470, sharing identical pin assignment and function mapping in the SOT23-5 footprint.