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Analog Devices Inc./Maxim Integrated MAX821RUS+T
- Part No.:
- MAX821RUS+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- TO-253-4, TO-253AA
- Datasheet:
-
MAX821RUS+T.pdf
- Description:
- IC MONITOR VOLT MPU SOT143-4
- Quantity:
- Payment:
- Shipping:
Inventory:7,488
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Product details
Overview
MAX821RUS+T from Maxim Integrated is an active-low microprocessor supervisory circuit in SOT143-4 package, monitoring +2.63V supply voltage with ±1.5% threshold accuracy over -40°C to +125°C, 2.5µA quiescent current, and pin-selectable reset timeout (1ms max / 20ms min / 100ms min) for reliable power-up sequencing in battery-powered controllers and portable instrumentation.
For engineers reviewing the MAX821RUS+T datasheet, MAX821RUS+T pinout, MAX821RUS+T application, or MAX821RUS+T equivalent, key selection criteria include guaranteed RESET validity down to VCC = 1V, immunity to fast VCC transients (<12µs at 100mV overdrive), SRT pin configuration options, and compatibility with 3V/5V digital systems requiring precise brownout detection.
Technical Context
The MAX821RUS+T implements a precision bandgap-based voltage comparator with 30ppm/°C tempco to detect VCC falling below 2.63V ±1.5%, triggering an active-low RESET signal that remains asserted for a user-defined timeout period determined solely by the SRT pin state (GND/VCC/open). Its internal timer resets on every VCC dip below threshold, ensuring robust brownout recovery.
No external components are required: the device integrates all timing, reference, and output drive circuitry. The RESET output guarantees logic-low state for VCC ≥1V and transitions cleanly without glitches during power transitions, with transient immunity validated up to 12µs for 100mV comparator overdrive.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.63V ±1.5% - precisely matches 2.7V system rails while allowing margin for regulation tolerance and temperature drift |
| Supply Current | 2.5µA typical - enables multi-year operation in coin-cell–powered devices without compromising supervision reliability |
| Operating Temp | -40°C to +125°C - supports automotive under-hood and industrial control environments without derating |
| Reset Timeout Options | 1ms (max), 20ms (min), or 100ms (min) - selected via SRT pin connection, enabling optimization for fast-boot or noise-immune systems |
| VCC Validity Range | RESET guaranteed low for VCC ≥1V - ensures deterministic reset assertion even during deep brownout or partial power collapse |
| Transient Immunity | Rejects <12µs negative VCC glitches at 100mV overdrive - eliminates false resets from switching noise or ESD-induced supply dips |
Pinout & Package
MAX821RUS+T is housed in a 4-pin SOT143 package (3.0mm × 1.6mm × 1.1mm), surface-mount, lead-free compliant. Pin 1 is GND, Pin 2 is active-low RESET, Pin 3 is SRT (Set Reset Timeout), and Pin 4 is VCC. The package supports reflow soldering per JEDEC J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Ground reference | Return path for internal comparator and output driver; must be low-impedance to ensure accurate threshold sensing |
| RESET (Pin 2) | Active-low reset output | Open-drain NMOS output sinking up to 1.2mA; requires external pull-up for µP interface; valid down to VCC = 1V |
| SRT (Pin 3) | Reset timeout select input | Three-state logic input: GND → 1ms max delay, VCC → 20ms min delay, open → 100ms min delay; <200pF loading required for open mode |
| VCC (Pin 4) | Supply voltage input | Accepts 1.0V to 5.5V; powers internal circuitry and defines reset threshold reference; tolerant of -0.3V to +6.0V absolute max |
Key Features
| Feature | Design Value |
|---|---|
| Pin-selectable reset timeout | Three discrete delay modes (1ms/20ms/100ms) set without resistors or capacitors-reduces BOM count and layout sensitivity |
| Precision 2.63V threshold | ±1.5% accuracy over full temperature range ensures consistent brownout detection across operating conditions |
| Ultra-low 2.5µA supply current | Enables permanent installation in energy-constrained systems such as handheld meters and wireless sensors |
| VCC = 1V RESET validity | Guaranteed active-low output state even when supply collapses to 1V-critical for fail-safe shutdown sequencing |
| Transient-immune comparator | Rejects sub-12µs supply glitches without external filtering-eliminates need for bulk capacitance on VCC rail |
Applications
| Bar-Code Scanners | Portable Medical Instruments |
|---|---|
Use Scenario: Handheld scanners powered by single Li-ion cells experience rapid VCC droop during laser activation and RF transmission bursts. IC Role / Device Role / Timing Role: MAX821RUS+T monitors VCC and asserts RESET if voltage falls below 2.63V, preventing corrupted scan data or firmware lockup during transient brownouts. Use Value: Ensures deterministic restart after power recovery without requiring software watchdog intervention or manual reset. | Use Scenario: Battery-operated glucose meters and pulse oximeters must retain calibration integrity and avoid spurious resets during low-battery operation. IC Role / Device Role / Timing Role: MAX821RUS+T provides guaranteed RESET assertion down to VCC = 1V, enabling safe shutdown before memory corruption or sensor misread occurs. Use Value: Extends usable battery life by 8–12% compared to higher-threshold supervisors, while maintaining functional safety compliance. |
| Industrial PLC I/O Modules | Smart Energy Meters |
Use Scenario: DIN-rail mounted I/O modules endure wide ambient temperature swings (-40°C to +85°C) and noisy 24VDC supply rails with ripple and transients. IC Role / Device Role / Timing Role: MAX821RUS+T supervises the 3.3V logic rail derived from the 24V bus, asserting RESET during undervoltage events while rejecting switching noise via built-in transient immunity. Use Value: Eliminates field failures caused by false resets due to 24V bus ripple, reducing warranty returns and service calls. | Use Scenario: Revenue-grade electricity meters operate continuously for 15+ years on backup supercapacitors during mains failure, requiring ultra-low-power supervision. IC Role / Device Role / Timing Role: MAX821RUS+T monitors the 3.0V backup rail with 2.5µA current draw, asserting RESET only on true brownout-not on brief capacitor discharge dips. Use Value: Prevents meter firmware corruption during extended outages while extending supercapacitor service life by minimizing unnecessary reset cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS3808G12DBVR | Fixed 1.2V threshold, 350ms fixed timeout, 1.4µA ICC - no SRT pin; requires external resistor for threshold adjustment | Designed for low-voltage ASICs; lacks 2.63V precision match and pin-selectable timing flexibility | Select when system uses 1.2V core rail and fixed long timeout suffices; not suitable for 2.63V/3V systems needing programmable delay |
| ADM6705LAKSZ-REEL7 | 2.63V threshold (±1.2%), 200ms fixed timeout, 3.5µA ICC - no SRT pin; includes manual reset input | Targets industrial controllers requiring manual reset capability; timeout not configurable per board design | Choose when manual reset button integration is mandatory and 200ms timeout aligns with system boot requirements |
Compared with TPS3808G12DBVR and ADM6705LAKSZ-REEL7, the MAX821RUS+T uniquely delivers 2.63V precision threshold with three factory-trimmed timeout options in a 4-pin SOT143, enabling minimal-footprint, zero-component supervision for 3V systems where timing flexibility and ultra-low ICC are critical.
Availability
MAX821RUS+T is available at Aetrix Electronics and suitable for bar-code scanners, portable medical instruments, industrial PLC I/O modules, smart energy meters, and battery-powered controllers requiring stable component supply across automotive, industrial, and medical end equipment.
Supply support for MAX821RUS+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 high-performance analog, mixed-signal, and power management ICs for demanding industrial, automotive, communications, and computing applications.
The MAX821 series targets cost-sensitive, space-constrained microprocessor supervision tasks where precision threshold matching, ultra-low power, and flexible reset timing are essential-especially in portable and battery-operated systems.
FAQ
What is the exact reset threshold voltage of the MAX821RUS+T and how is it trimmed?
The MAX821RUS+T has a nominal reset threshold of 2.63V with ±1.5% accuracy over -40°C to +125°C. This value is factory-trimmed using laser or fuse techniques during wafer sort and is specified in the Electrical Characteristics table under "VTH" for ordering option "R". No external calibration is required.
How does the SRT pin configure the reset timeout delay on the MAX821RUS+T?
The SRT pin on the MAX821RUS+T selects one of three timeout modes: connect to GND for ≤1ms delay, connect to VCC for ≥20ms delay, or leave unconnected (with <200pF parasitic capacitance) for ≥100ms delay. The internal timer starts counting only after VCC rises above 2.63V and resets on every subsequent threshold crossing.
Is the MAX821RUS+T compatible with 3.3V microcontrollers and what is its RESET output behavior?
Yes, the MAX821RUS+T is fully compatible with 3.3V µCs. Its active-low RESET output is open-drain and sinks up to 1.2mA at VCC ≥2.63V. It remains valid (guaranteed low) down to VCC = 1V, and requires an external pull-up resistor (typically 10kΩ to 3.3V) to interface with standard CMOS inputs.
Does the MAX821RUS+T require any external components for basic operation?
No, the MAX821RUS+T requires zero external components for core supervision functionality. Only an external pull-up resistor on the RESET pin is needed for interfacing with most µPs. No timing capacitors, resistors, or reference sources are necessary-enabling minimal PCB footprint and simplified qualification.
What is the maximum VCC transient duration the MAX821RUS+T can reject without asserting reset?
The MAX821RUS+T rejects negative-going VCC transients up to 12µs in duration when the overdrive (VTH – VCC) is 100mV, as characterized in Figure 1 of the datasheet. Transient rejection degrades as overdrive increases; for example, a 200mV overdrive limits immunity to ~5µs. A 0.1µF ceramic capacitor near VCC further enhances immunity.
MAX821RUS+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- TO-253-4, TO-253AA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Power Supply Monitor
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 2.63V
- Output:
- Push-Pull, Totem Pole
- Reset:
- Active Low
- Reset Timeout:
- 100ms Minimum
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-143-4
MAX821RUS+T FAQ
1.How can I place an order for MAX821RUS+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX821RUS+T on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MAX821RUS+T reliable?
The price and inventory of MAX821RUS+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX821RUS+T is usually 5 days.
3.What payment methods are accepted for MAX821RUS+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX821RUS+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX821RUS+T?
MAX821RUS+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX821RUS+T order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MAX821RUS+T?
For technical support, including MAX821RUS+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX821RUS+T requirements.
6.How does Aetrix verify that MAX821RUS+T is sourced from the original manufacturer or authorized distributors?
All MAX821RUS+T products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MAX821RUS+T meets industry standards.
7.What is the process for return or replacement of MAX821RUS+T?
All MAX821RUS+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX821RUS+T, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MAX821RUS+T part is unused and in its original packaging.
Return procedure for MAX821RUS+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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