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Analog Devices Inc./Maxim Integrated MAX821LUS+T
- Part No.:
- MAX821LUS+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- TO-253-4, TO-253AA
- Datasheet:
-
MAX821LUS+T.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL SOT143-4
- Quantity:
- Payment:
- Shipping:
Inventory:999
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Product details
Overview
MAX821LUS+T from Maxim Integrated is an active-low microprocessor supervisory circuit in SOT143-4 package, monitoring 4.38V nominal VCC supply with ±1.5% reset threshold accuracy over -40°C to +125°C, 2.5µA quiescent current, and pin-selectable 1ms/20ms/100ms reset timeout - used for reliable power-on reset assertion in portable µP systems.
For engineers reviewing the MAX821LUS+T datasheet, MAX821LUS+T pinout, MAX821LUS+T application, or MAX821LUS+T equivalent, key selection criteria include guaranteed RESET validity down to VCC = 1V, immunity to sub-12µs VCC transients ≥100mV below threshold, and SRT pin configuration for deterministic timeout selection without external components.
Technical Context
The MAX821LUS+T implements a precision bandgap-based voltage comparator with 30ppm/°C tempco to detect VCC falling below 4.38V (±1.5%), asserting active-low RESET until VCC recovers and the internal timer expires. Its SRT input directly configures timeout via GND/VCC/open states - no logic decoding required.
Designed for single-function reliability, it excludes watchdog or manual reset features; reset assertion is purely voltage-triggered with transient immunity achieved through comparator hysteresis and internal filtering - no external RC network needed for basic operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Nominal VTH | 4.38V - precisely matches 5V-system brownout detection margin before logic failure |
| Reset Threshold Accuracy | ±1.5% over full temperature range - ensures deterministic reset assertion across industrial environments |
| Supply Current | 2.5µA at +25°C - enables multi-year battery life in always-on portable instrumentation |
| Operating Temp Range | -40°C to +125°C - qualified for under-hood automotive and industrial control applications |
| RESET Validity | Guaranteed low state down to VCC = 1V - maintains valid reset signal during deep brownout recovery |
| Timeout Options | 1ms (max), 20ms (min), or 100ms (min) - selected by SRT pin connection, no firmware or external timing components |
| VCC Transient Immunity | Rejects ≤12µs glitches ≥100mV below VTH - prevents spurious resets from switching noise or ESD coupling |
Pinout & Package
SOT143-4 surface-mount package: 1.3mm × 2.1mm footprint, 0.95mm height, gull-wing leads, RoHS-compliant lead-free finish (indicated by "+T" suffix).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Reference ground | 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 at VTH(min); requires external pull-up for logic-high level |
| SRT (Pin 3) | Timeout select input | Three-state logic: GND → 1ms max, VCC → 20ms min, open → 100ms min; <200pF loading required for open mode |
| VCC (Pin 4) | Supply input | Monitored voltage rail; operates from 1.0V to 5.5V; internal regulator powers comparator and timer independently |
Key Features
| Feature | Design Value |
|---|---|
| Pin-selectable reset timeout | Hardware-configured delay (1ms/20ms/100ms) eliminates firmware dependency and timing uncertainty in boot sequence |
| Guaranteed RESET down to VCC = 1V | Ensures continuous reset assertion during slow discharge of bulk capacitors, preventing partial initialization |
| 2.5µA supply current | Reduces standby power in battery-backed systems by >95% versus discrete reset IC alternatives |
| 30ppm/°C reset threshold tempco | Maintains ±1.5% accuracy across full -40°C to +125°C range without calibration or trimming |
| VCC transient immunity | Rejects fast glitches (≤12µs, ≥100mV undershoot) without requiring external RC snubbers or ferrite beads |
Applications
| Bar-Code Scanners | Portable Medical Instruments |
|---|---|
Use Scenario: Handheld scanners powered by single-cell Li-ion batteries experiencing voltage sag during laser activation. IC Role / Device Role / Timing Role: Supervisory circuit asserting active-low RESET during VCC dip below 4.38V, holding µP in reset until stable 5V rail resumes and 20ms timeout completes. Use Value: Prevents corrupted scan data and firmware crashes caused by marginal VCC during high-current pulses. | Use Scenario: Battery-powered glucose meters requiring guaranteed boot integrity after cold storage (-20°C) and rapid warm-up. IC Role / Device Role / Timing Role: Voltage monitor validating 5V supply stability before enabling ADC and display drivers, with 100ms timeout ensuring full LDO settling. Use Value: Eliminates false readings from incomplete power-rail sequencing in temperature-variable clinical environments. |
| Industrial PLC I/O Modules | Automotive Body Control Units |
Use Scenario: DIN-rail mounted controllers exposed to 12V bus transients during relay switching and load dump events. IC Role / Device Role / Timing Role: Reset supervisor detecting 5V rail collapse from upstream DC/DC failure, asserting RESET for 1ms to synchronize recovery across distributed nodes. Use Value: Enables deterministic multi-node restart without software coordination, reducing system-level fault propagation risk. | Use Scenario: Under-dash modules subjected to cold-crank (4.5V) and load-dump (28V) conditions per ISO 7637-2. IC Role / Device Role / Timing Role: Primary reset generator for microcontroller domain, monitoring post-regulator 5V rail with 20ms timeout to accommodate slow-start LDOs. Use Value: Meets AEC-Q100 Grade 1 requirements for reset validity and thermal stability without derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage supervisor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS3808G12DBVR | Fixed 1.2V threshold; 200ms timeout; 1.8µA ICC; requires external resistor for threshold adjustment | Targeted at ultra-low-voltage systems (1.2V–5.5V), not optimized for 4.38V 5V-rail monitoring | Select when precise 1.2V supervision is required and longer timeout improves robustness against slow-rising rails |
| ADM6710LAKSZ-REEL7 | 4.38V threshold; 200ms timeout; 3.5µA ICC; fixed timeout, no SRT pin | Lacks hardware-programmable timeout - requires PCB redesign to change delay | Choose when design freeze prohibits SRT routing and 200ms delay satisfies system boot timing constraints |
Compared with TPS3808G12DBVR and ADM6710LAKSZ-REEL7, the MAX821LUS+T uniquely delivers factory-trimmed 4.38V threshold with field-selectable timeout in a 4-pin SOT143, enabling one-BOM flexibility across multiple boot-time requirements without layout changes.
Availability
MAX821LUS+T is available at Aetrix Electronics and suitable for bar-code scanners, portable medical instruments, industrial PLC I/O modules, and automotive body control units requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for MAX821LUS+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 industrial, automotive, communications, and computing applications.
The MAX821LUS+T belongs to Maxim's µP supervisory product line, engineered specifically for deterministic, low-power reset generation in space-constrained embedded systems where supply voltage integrity is mission-critical.
FAQ
What is the exact reset threshold voltage for MAX821LUS+T?
The MAX821LUS+T has a nominal reset threshold of 4.38V with ±1.5% accuracy over -40°C to +125°C. This value is factory-trimmed and specified in the Ordering Information table of the datasheet. It is designed to reliably detect brownout conditions on standard 5V power rails while maintaining sufficient margin above minimum µP operating voltage.
How does the SRT pin configure the reset timeout on MAX821LUS+T?
The SRT pin on MAX821LUS+T selects reset timeout via three hardware states: connect to GND for 1ms (maximum), connect to VCC for 20ms (minimum), or leave unconnected for 100ms (minimum). Capacitive loading on SRT must remain below 200pF when open to prevent unintended timeout selection - verified in the Typical Operating Characteristics plots.
Is MAX821LUS+T compatible with 3V systems?
No - MAX821LUS+T is specifically configured for 4.38V threshold monitoring and is intended for 5V-rail applications. For 3V systems, Maxim offers variants like MAX821TUS+T (3.08V threshold) or MAX821SUS+T (2.93V threshold); the "L" suffix in MAX821LUS+T explicitly denotes the 4.38V version per the top-marking code AZ_ _.
Does MAX821LUS+T provide watchdog functionality?
No, MAX821LUS+T provides only power-supply voltage monitoring and power-on reset generation. It lacks watchdog timer, manual reset input, or window-detection capability. Its sole function is asserting active-low RESET when VCC falls below 4.38V and holding it for the SRT-selected timeout after recovery - confirmed in the General Description and Detailed Description sections.
What is the minimum VCC required for MAX821LUS+T to maintain valid RESET output?
The MAX821LUS+T guarantees valid active-low RESET output down to VCC = 1V, as explicitly stated in the Features list and Detailed Description. Below 1V, the RESET output becomes high-impedance; for operation down to 0V, a 100kΩ pull-down resistor is recommended per Figure 2a in the datasheet.
MAX821LUS+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:
- Simple Reset/Power-On Reset
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.63V
- Output:
- Push-Pull, Totem Pole
- Reset:
- Active Low
- Reset Timeout:
- Adjustable/Selectable
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-143-4
MAX821LUS+T FAQ
1.How can I place an order for MAX821LUS+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX821LUS+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 MAX821LUS+T reliable?
The price and inventory of MAX821LUS+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX821LUS+T is usually 5 days.
3.What payment methods are accepted for MAX821LUS+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX821LUS+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX821LUS+T?
MAX821LUS+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX821LUS+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 MAX821LUS+T?
For technical support, including MAX821LUS+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX821LUS+T requirements.
6.How does Aetrix verify that MAX821LUS+T is sourced from the original manufacturer or authorized distributors?
All MAX821LUS+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 MAX821LUS+T meets industry standards.
7.What is the process for return or replacement of MAX821LUS+T?
All MAX821LUS+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX821LUS+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 MAX821LUS+T part is unused and in its original packaging.
Return procedure for MAX821LUS+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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