Analog Devices Inc./Maxim Integrated MAX6368HKA31+

Overview

The MAX6368HKA31+ from Maxim Integrated is a low-power microprocessor supervisory circuit with auxiliary user-adjustable reset input, battery backup switchover, and chip-enable gating. It monitors VCC supply voltage (reset threshold 3.00V–3.15V), provides active-high open-drain RESET output, operates down to 1.2V supply, and supports CMOS RAM write protection in brownout conditions. Used in portable industrial controllers requiring reliable power-fail response and secondary supply monitoring.

For engineers reviewing the MAX6368HKA31+ datasheet, MAX6368HKA31+ pinout, MAX6368HKA31+ application, or MAX6368HKA31+ equivalent, key selection criteria include its 1.235V internal RESET IN comparator threshold, 150ms minimum reset timeout, 10µA quiescent current, SOT23-8 package, and support for dual-supply undervoltage detection via external resistor divider.

Technical Context

The MAX6368HKA31+ integrates a precision voltage monitor for VCC (factory-set 3.08V nominal threshold), an independent 1.235V reference-based comparator for the RESET IN pin, and a bidirectional transmission gate for CE IN/CE OUT with 1.5ns propagation delay. Its battery switchover logic activates when VCC falls below both VTH and VBATT by ≥20mV, switching OUT from VCC to BATT with hysteresis to prevent chatter.

RESET assertion is triggered by VCC falling below 3.08V, RESET IN falling below 1.235V, or MR (if present) going low - but only MAX6368 variants use RESET IN; no manual reset or watchdog functionality is included. The open-drain active-high RESET output remains asserted for ≥150ms after recovery and is guaranteed functional down to 1.2V VCC or VBATT.

Key Specifications

Pinout & Package

MAX6368HKA31+ is housed in an 8-pin SOT23 package (2.9mm × 1.6mm × 1.1mm), surface-mount, lead(Pb)-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6367HKA31+, MAX6368HKA31+ trades BATT ON status signaling for flexible secondary supply monitoring via RESET IN; compared with TPS3808G33DBVR, it adds full battery backup, CE gating, and adjustable reset input at higher pin count and current consumption.

Availability

MAX6368HKA31+ is available at Aetrix Electronics and suitable for industrial data loggers, medical portable monitors, POS terminals, ruggedized telematics units, and battery-backed memory systems requiring stable component supply across extended temperature ranges.

Supply support for MAX6368HKA31+ 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, automotive, and computing applications.

The MAX6365–MAX6368 family delivers integrated power-supply supervision, battery backup control, and memory write protection in ultra-small SOT23 packages for space-constrained µP systems.

FAQ

What is the factory-set reset threshold voltage for MAX6368HKA31+?

The MAX6368HKA31+ has a factory-set VCC reset threshold of 3.00V (min), 3.08V (typ), and 3.15V (max). This range is optimized for reliable supervision of 3.3V logic rails during brownout conditions. The threshold is laser-trimmed at wafer test and does not require external components. This specification applies across the full -40°C to +85°C operating temperature range and is guaranteed by design per the datasheet's Electrical Characteristics table.

How does the RESET IN pin function on MAX6368HKA31+?

The RESET IN pin on MAX6368HKA31+ connects to an internal 1.235V precision reference comparator. When the voltage at RESET IN falls below 1.185V (min), the device asserts RESET. This enables monitoring of secondary supplies (e.g., 5V analog, 2.5V sensor rails) using an external resistor divider. The input leakage is ±25nA max, allowing use of high-value resistors (e.g., 100kΩ/273kΩ) without accuracy loss. RESET IN assertion holds RESET active for ≥150ms after the pin rises above threshold.

What package type and dimensions does MAX6368HKA31+ use?

MAX6368HKA31+ uses an 8-pin SOT23 package measuring 2.9mm × 1.6mm × 1.1mm (L × W × H) with standard 0.65mm lead pitch. It is lead(Pb)-free, RoHS-compliant, and marked "AACX" on top. The package supports reflow soldering per JEDEC J-STD-020, with peak reflow temperature of +260°C for lead-free profiles. Thermal resistance θ_JA is 210°C/W, and maximum continuous power dissipation at +70°C is 700mW.

Does MAX6368HKA31+ support battery backup switchover, and what are the conditions?

Yes, MAX6368HKA31+ supports automatic battery backup switchover. Switchover engages when two conditions are met simultaneously: (1) VCC falls below the reset threshold (3.08V), and (2) VCC is at least 20mV lower than VBATT. Once engaged, OUT is sourced from BATT instead of VCC. A 40mV hysteresis (20mV up, 20mV down) prevents oscillation during slow VCC decay. The device draws only 3µA from BATT in backup mode (VBATT = 2.8V, VCC = 0V), ensuring long hold-up time.

What is the purpose of the CE IN and CE OUT pins on MAX6368HKA31+?

The CE IN and CE OUT pins implement chip-enable signal gating to prevent memory corruption during power faults. During normal operation, CE IN passes through to CE OUT with 1.5ns propagation delay. When RESET asserts, CE OUT is forced low for 12µs (typ) if CE IN was low, ensuring ongoing memory read/write completes. If CE IN is high during reset, CE OUT remains high. This feature protects SRAM and EEPROM from partial writes caused by brownout, and is critical for systems requiring data integrity across power interruptions.