Analog Devices Inc./Maxim Integrated MAX822MUS-T

Overview

MAX822MUS-T from Maxim Integrated is an active-high microprocessor supervisory IC that monitors +3V to +5V power supplies and asserts a reset signal when VCC falls below 4.38V (typical threshold), maintaining reset for a pin-selectable timeout of 1ms (max), 20ms (min), or 100ms (min). It operates over –40°C to +125°C, draws only 2.5µA supply current, and uses a 4-pin SOT143 package-ideal for portable equipment and critical µP power monitoring in bar-code scanners and controllers.

For engineers reviewing the MAX822MUS-T datasheet, MAX822MUS-T pinout, MAX822MUS-T application, or MAX822MUS-T equivalent, key selection criteria include its guaranteed active-high RESET output valid down to VCC = 1.2V, precision 4.38V reset threshold with ±1.5% accuracy over temperature, immunity to fast VCC transients (<12µs at 100mV overdrive), and compatibility with leaded or lead-free assembly via -T/+T suffix options.

Technical Context

The MAX822MUS-T implements a dedicated voltage-monitoring comparator with hysteresis and an internal timer controlled by the SRT pin. Its reset assertion logic is strictly level-sensitive: RESET goes high when VCC drops below the 4.38V threshold and remains high for the full timeout period after VCC recovers above threshold-even if brownouts recur mid-timer.

Unlike programmable supervisors, it offers no watchdog or manual reset input; its sole function is single-event power-on/brownout reset generation. The SRT pin supports three discrete timeout modes (GND = 1ms, VCC = 20ms, open = 100ms), with capacitive loading on SRT strictly limited to <200pF for reliable 100ms selection.

Key Specifications

Pinout & Package

SOT143-4 package: ultra-compact 1.3mm × 2.1mm surface-mount outline with gull-wing leads, optimized for space-constrained portable PCBs and compatible with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX822LUS-T, the MAX822MUS-T provides tighter threshold alignment with 5V ±5% rails; versus TLV803EB29DBZR, it delivers configurable timing and higher voltage rating but requires SOT143 routing and has higher unit cost.

Availability

MAX822MUS-T is available at Aetrix Electronics and suitable for portable medical devices, industrial PLC controllers, smart energy meters, and bar-code scanners requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX822MUS-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 and mixed-signal ICs for demanding industrial, automotive, and communications applications-with emphasis on reliability, low power, and integration.

The MAX821/MAX822 product line delivers cost-effective, single-function µP supervisory circuits targeting space-constrained and battery-operated systems needing guaranteed reset assertion during power faults.

FAQ

What is the exact reset threshold voltage for MAX822MUS-T, and how does it vary with temperature?

The MAX822MUS-T has a nominal reset threshold of 4.38V, with guaranteed minimum/maximum values of 4.31V and 4.45V over –40°C to +125°C. Its tempco is ±30ppm/°C, meaning threshold drift is bounded to ±0.013V across the full range-sufficient for stable operation in automotive and industrial environments without calibration.

Can MAX822MUS-T be used in 3.3V systems, and what are the implications?

The MAX822MUS-T is specified for 4.38V threshold and requires VCC ≥1.2V to guarantee RESET validity, but it is not recommended for 3.3V systems because its threshold exceeds the 3.3V rail by >30%. Using it risks failure to assert reset during actual brownout. For 3.3V, select MAX822TUS-T (3.08V threshold) or MAX822SUS-T (2.93V).

How does the SRT pin configuration affect reset timeout, and what happens if it's left floating unintentionally?

Connecting SRT to GND selects 1ms (max) timeout, to VCC selects 20ms (min), and leaving it unconnected selects 100ms (min). If unintentionally floating due to PCB leakage or contamination, SRT may settle near intermediate voltage, causing unpredictable timeout-always tie SRT explicitly to GND, VCC, or use a pull-up/down resistor per design intent.

Does MAX822MUS-T support lead-free soldering, and how is RoHS compliance indicated in the part number?

Yes, MAX822MUS-T supports lead-free soldering with standard reflow profiles. RoHS-compliant versions use the "+T" suffix (e.g., MAX822MUS+T); the "-T" suffix denotes tape-and-reel packaging but does not imply lead-free status. Always verify materials analysis reports for specific lot traceability and exemption status.

What is the maximum capacitive load allowed on the SRT pin for reliable 100ms timeout operation?

For guaranteed 100ms timeout when SRT is unconnected, total capacitive loading-including PCB trace, probe, and stray capacitance-must be kept below 200pF. Exceeding this limit slows SRT node charging, potentially causing the internal timer to interpret the condition as a VCC-connected state and default to 20ms timeout instead.