Analog Devices Inc./Maxim Integrated MAX6391KA23-T

Overview

MAX6391KA23-T from Maxim Integrated is a dual-voltage microprocessor supervisory circuit with sequenced open-drain reset outputs, monitoring VCC (2.32V factory-fixed threshold) and adjustable RESET IN2 (625mV reference), delivering 140ms minimum timeout on RESET1 and fixed or capacitor-adjustable timeout on RESET2 for controlled power-up sequencing in multivoltage systems.

For engineers reviewing the MAX6391KA23-T datasheet, MAX6391KA23-T pinout, MAX6391KA23-T application, or MAX6391KA23-T equivalent, this device supports precise reset ordering between master and slave supplies, guarantees valid reset operation down to VCC = 1V, and integrates internal 47kΩ pullup resistors for independent VOH level setting-critical for industrial controllers, servers, and multirail embedded systems requiring deterministic startup behavior.

Technical Context

The MAX6391KA23-T implements two independent voltage-monitoring comparators: one for VCC (with 2.32V ±5% threshold) and one for RESET IN2 (625mV reference), enabling dual-supply supervision where RESET1 responds only to VCC while RESET2 responds to either supply. RESET2 deasserts only after both VCC and RESET IN2 exceed thresholds and RESET1 has deasserted-enforcing strict power-up sequence.

RESET1 uses an internal timer with guaranteed 140ms minimum timeout; RESET2 timing is selectable via CSRT pin connection-tied to VCC for fixed 140ms min delay or to external capacitor for user-adjustable delay (e.g., 3.1ms with 1500pF). The device operates from 1.2V to 5.5V and draws only 15µA typical supply current.

Key Specifications

Pinout & Package

MAX6391KA23-T is housed in an 8-pin SOT23 package (JEDEC MO-178 compliant, 1.95mm × 2.80mm footprint, 1.45mm height), optimized for space-constrained PCB layouts in industrial and computing applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-voltage supervisory applications.

Compared with MAX6391KA23-T, MAX6392KA23-T adds manual reset but sacrifices R1 pin and changes RESET1 drive type, while TPS3808G33DBVR lacks dual-monitor capability entirely-neither offers pin-compatible replacement, and both require schematic and layout revision to implement.

Availability

MAX6391KA23-T is available at Aetrix Electronics and suitable for industrial controllers, servers/workstations, and set-top boxes requiring stable component supply, long-term lifecycle support, and guaranteed reset timing across -40°C to +85°C.

Supply support for MAX6391KA23-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, mixed-signal, and power-management ICs for demanding industrial, computing, and communications applications.

The MAX6391/MAX6392 product line delivers sequenced dual-supply supervision for multivoltage systems-specifically engineered to replace discrete reset solutions in servers, controllers, and embedded platforms where power-up order integrity is critical.

FAQ

What is the factory-set VCC reset threshold voltage for MAX6391KA23-T?

The MAX6391KA23-T has a factory-set VCC reset threshold of 2.32V, with ±5% tolerance across temperature. This value is laser-trimmed during production and applies specifically to the KA23 variant-confirmed in the Selector Guide and Electrical Characteristics table. The MAX6391KA23-T uses this threshold to assert RESET1 whenever VCC drops below 2.32V, and it remains asserted for at least 140ms after VCC recovers.

Can MAX6391KA23-T monitor a 1.8V supply as the secondary voltage?

Yes, MAX6391KA23-T can monitor a 1.8V supply using the RESET IN2 pin with an external resistor divider. Since the internal reference is 625mV, a divider with R3 = 925kΩ and R4 = 500kΩ yields VRST ≈ 1.8V. The MAX6391KA23-T's high-impedance RESET IN2 input draws only 50nA, minimizing divider current. This configuration allows precise supervision of 1.8V rails while maintaining full compatibility with the MAX6391KA23-T's sequenced reset architecture.

How is the RESET2 timeout period configured on MAX6391KA23-T?

The RESET2 timeout on MAX6391KA23-T is configured via the CSRT pin: connecting CSRT to VCC selects a fixed 140ms minimum delay, while connecting CSRT to a capacitor-to-ground enables user-adjustable timing (e.g., 3.1ms with 1500pF). The MAX6391KA23-T contains an internal 600nA current source that ramps voltage across the capacitor; the time to reach 1.25V determines the delay. This dual-mode flexibility is intrinsic to the MAX6391KA23-T and requires no external logic or firmware.

Does MAX6391KA23-T provide internal pullup resistors for both reset outputs?

Yes, MAX6391KA23-T integrates two 47kΩ internal pullup resistors-one connected to RESET1 (via R1 pin) and one to RESET2 (via R2 pin). These allow independent connection to different VOH rails (e.g., 3.3V for RESET1, 5V for RESET2) without external components. Unlike many supervisors, the MAX6391KA23-T places full control of pullup voltage selection directly on the user via dedicated R1/R2 terminals-no compromise on voltage level or current drive.

Is MAX6391KA23-T compatible with lead-free assembly processes?

Yes, MAX6391KA23-T is available in lead-free packaging-specified by replacing the "-T" suffix with "+T" per Maxim's ordering guide. The SOT23-8 package meets JEDEC J-STD-020 moisture sensitivity level 1 and supports standard Pb-free reflow profiles (peak 260°C). The MAX6391KA23-T's BiCMOS process and 150°C junction rating ensure robust thermal performance during lead-free soldering, and its 1.2V–5.5V operating range accommodates post-reflow voltage margin requirements.