The MAX6365-MAX6368 from Maxim Integrated (now part of Analog Devices) are low-power µP supervisory circuits that do three jobs at once: monitor the supply and hold the processor in reset until it is valid, switch a backup battery in when the main supply fails, and gate the chip-enable so external CMOS RAM cannot be corrupted during a power transition. The MAX6368 is the version with an auxiliary user-adjustable RESET IN. MAX6368LKA29+T is the RoHS ("+"), tape-and-reel ("T") option in 8-pin SOT23; the "29" sets the reset threshold at 2.93 V and the "L" selects the push-pull RESET output.

The supervisor watches V_CC against the factory-trimmed 2.93 V threshold. When V_CC falls below it - on power-up, power-down or a brownout - the device asserts RESET and holds it for a guaranteed 150 ms minimum after V_CC recovers, giving the processor a clean start. The RESET/RESET̅ outputs are valid down to 1.2 V of V_CC or V_BATT, so the reset stays asserted even as the rail collapses. Power-supply transient immunity prevents false resets on short glitches.

For non-volatile memory, the battery-backup and chip-enable gating work together. The OUT pin powers the RAM from V_CC normally and switches to the BATT input when the main supply fails, so data is retained. At the same time, the supervisor passes the processor's CE IN through to CE OUT only while the supply is valid - blocking writes during power transitions to protect memory contents. The MAX6368 adds the auxiliary RESET IN comparator so a second voltage (a different rail or a divided input) can also force a reset.

Note: Values are taken from the Maxim MAX6365-MAX6368 datasheet. Confirm every parameter (especially the exact threshold and RESET polarity for the LKA29 code) against the latest official documentation before committing a design.

MAX6368LKA29+T ships in the 8-pin SOT23 - the small surface-mount body that lets a full supervisor with battery backup and CE gating sit beside the processor and its CMOS RAM. Keep the BATT trace clean to the coin cell, route the RAM supply from OUT, and pass the memory chip-enable through CE IN/CE OUT. Bypass V_CC at the pin. The package image is shown below.

The 8-pin SOT23 carries the reset, battery-backup and chip-enable signals (MAX6368 pin configuration, per the MAX6365-MAX6368 datasheet):

• Pin 1 - RESET̅/RESET: Reset output (push-pull on the L grade); asserted while V_CC is below threshold and for 150 ms after.
• Pin 2 - CE IN: Chip-enable input from the processor.
• Pin 3 - GND: Ground.
• Pin 4 - RESET IN: Auxiliary user-adjustable reset comparator input (monitors a second voltage); tie to V_CC if unused.
• Pin 5 - V_CC: Main supply input (monitored).
• Pin 6 - OUT: Backup-switched output to CMOS RAM (V_CC normally, V_BATT on power-fail).
• Pin 7 - BATT: Backup-battery input.
• Pin 8 - CE OUT: Gated chip-enable output to memory (blocked during power transitions).

Within the MAX6365-MAX6368 family the variants differ by feature: the MAX6365 has a manual-reset input, the MAX6366 a watchdog, the MAX6367 a battery-on output and power-fail comparator, and the MAX6368 (this part) the auxiliary RESET IN. Related power-management parts are listed below.

Selection Tips: Choose the MAX6368 when you need a µP supervisor with battery backup, chip-enable gating and an auxiliary adjustable RESET IN at a 2.93 V threshold. Within the family the MAX6365 (manual reset), MAX6366 (watchdog) and MAX6367 (battery-on/power-fail) cover other feature sets; the threshold and RESET polarity are set by the part-code suffix.

Maxim Integrated, now part of Analog Devices, Inc. (ADI), built the MAX6365-MAX6368 to combine reset supervision, battery-backup switchover and memory write-protection in one SOT23 - the housekeeping a microprocessor system needs to start cleanly and keep its data through a power loss.

ADI maintains the datasheet, the threshold/timeout/polarity option tables and the battery-backup and CE-gating application guidance for the family - the documentation behind a reliable supervisory design.