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Analog Devices Inc./Maxim Integrated MAX821MUS+T
- Part No.:
- MAX821MUS+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- TO-253-4, TO-253AA
- Datasheet:
-
MAX821MUS+T.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL SOT143-4
- Quantity:
- Payment:
- Shipping:
Inventory:4,710
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Product details
Overview
MAX821MUS+T from Maxim Integrated is an active-low microprocessor supervisory circuit in SOT143-4 package, monitoring +4.38V nominal 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) - used for reliable power-on reset assertion in portable µP systems.
For engineers reviewing the MAX821MUS+T datasheet, MAX821MUS+T pinout, MAX821MUS+T application, or MAX821MUS+T equivalent, this page delivers verified electrical parameters, thermal performance data, SRT input configuration logic, reset timing behavior under brownout, and design guidance for interfacing with bidirectional µP reset pins and low-voltage validity down to VCC = 1V.
Technical Context
The MAX821MUS+T implements a precision bandgap-based reset comparator with 30ppm/°C tempco and guaranteed operation from VCC = 1V, asserting active-low RESET only when VCC falls below 4.38V (±1.5%) and holding it low for the SRT-configured timeout after recovery. Its internal timer resets on every VCC dip below threshold, ensuring robust brownout response.
Reset immunity to fast transients is achieved via comparator hysteresis and filtering; typical immunity allows ≤12µs negative-going VCC glitches of 100mV amplitude without spurious reset. The SRT pin accepts three discrete states - GND, VCC, or open - each selecting a distinct timeout mode with defined min/max bounds and temperature stability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Nominal Reset Threshold | 4.38V - matches standard +5V system rails with margin above minimum µP operating voltage. |
| 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 portable equipment without compromising supervision integrity. |
| Reset Timeout Options | 1ms (max), 20ms (min), or 100ms (min) - selected by SRT pin state, supporting fast-boot or legacy-timing requirements. |
| Operating Temperature | -40°C to +125°C - qualified for under-hood automotive, industrial control, and harsh-environment embedded use. |
| VCC Validity Range | RESET guaranteed valid down to VCC = 1V - maintains known logic state during deep brownout before power collapse. |
| Transient Immunity | Rejects ≤12µs, 100mV VCC dips - prevents false resets from switching noise or ESD-induced supply disturbances. |
Pinout & Package
SOT143-4 surface-mount package (1.3mm × 2.1mm × 0.95mm), thermally enhanced with exposed pad (not electrically connected), JEDEC-compliant lead-free finish (indicated by "+T" suffix).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - GND | Ground reference | Return path for internal comparator and output driver; must be low-impedance to ensure accurate threshold sensing. |
| 2 - RESET | Active-low reset output | Open-drain NMOS output sinking up to 1.2mA; requires external pull-up; asserts low during VCC fault and timeout period. |
| 3 - SRT | Set Reset Timeout input | Three-state logic input: GND → 1ms max delay; VCC → 20ms min delay; open → 100ms min delay; <200pF loading required for open mode. |
| 4 - VCC | Supply voltage input | Monitored rail input (4.38V nominal); powers internal circuitry and defines reset comparator reference point. |
Key Features
| Feature | Design Value |
|---|---|
| Pin-selectable reset timeout | Three discrete delay modes (1ms/20ms/100ms) configured without resistors or firmware - reduces BOM count and layout complexity. |
| Precision voltage monitoring | 4.38V threshold with ±1.5% tolerance over -40°C to +125°C - eliminates need for external trimming or calibration in production. |
| Ultra-low supply current | 2.5µA typical ICC - enables integration into always-on subsystems without measurable battery drain impact. |
| Brownout immunity | Internal timer resets on every VCC dip below threshold - guarantees reset reassertion even during repeated supply sag events. |
| VCC = 1V reset validity | RESET remains actively driven low down to VCC = 1V - ensures µP stays held in reset until supply is fully collapsed. |
Applications
| Bar-Code Scanners | Portable Medical Devices |
|---|---|
|
Use Scenario: Handheld scanners powered by single-cell Li-ion batteries experiencing rapid voltage droop during laser activation and motor startup. IC Role / Device Role / Timing Role: Supervisory circuit asserting active-low reset to prevent µP code corruption during transient brownouts. Use Value: 1ms timeout option enables fast wake-up after brief interruptions while maintaining immunity to 12µs switching noise. |
Use Scenario: Battery-powered glucose meters requiring guaranteed reset during cold-weather battery voltage sag below 3.0V. IC Role / Device Role / Timing Role: Voltage monitor holding µP in reset until VCC recovers above 4.38V and sustains for ≥100ms. Use Value: 100ms timeout prevents premature boot during marginal battery recovery; -40°C to +125°C rating covers clinical and field use. |
| Industrial PLC I/O Modules | Automotive Body Control Units |
|
Use Scenario: DIN-rail mounted controllers exposed to 24V supply ripple and load-dump transients in factory environments. IC Role / Device Role / Timing Role: Primary reset supervisor validating clean 5V local rail before enabling FPGA configuration sequence. Use Value: 20ms timeout aligns with FPGA power-good timing; 30ppm/°C tempco ensures stable threshold across ambient shifts. |
Use Scenario: Under-dash modules subjected to wide temperature swings and ignition-switch bounce during cold cranking. IC Role / Device Role / Timing Role: Brownout detector asserting reset during VCC collapse below 4.38V and holding until stable for 100ms post-cranking. Use Value: Guaranteed operation to +125°C and VCC = 1V reset validity prevent spurious restarts during engine start transients. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX809SEUR+T | Fixed 3.08V threshold, 240ms reset timeout, same SOT143-4 package and 2.5µA ICC. | Lacks pin-selectable timeout; suited for systems requiring longer fixed delay and lower-voltage monitoring. | Select when fixed 3.08V threshold and 240ms delay meet system timing, avoiding SRT pin routing. |
| TPS3808G12QDBVRQ1 | Automotive-grade (AEC-Q100), 3.08V threshold, adjustable timeout via external capacitor (1.2ms–10s), 1.8µA ICC. | Requires external RC network; supports wider timeout range but adds component count and layout sensitivity. | Choose for automotive qualification and programmable delay flexibility where SOT143 footprint is acceptable. |
Compared with MAX821MUS+T, MAX809SEUR+T offers simpler fixed-delay supervision at lower voltage but no timeout configurability, while TPS3808G12QDBVRQ1 provides AEC-Q100 compliance and broader timeout tuning at the cost of added passive components and higher design overhead.
Availability
MAX821MUS+T is available at Aetrix Electronics and suitable for portable medical devices, industrial PLC I/O modules, bar-code scanners, automotive body control units, and battery-powered instrumentation requiring stable component supply across extended temperature ranges.
Supply support for MAX821MUS+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, mixed-signal, and power management ICs for demanding industrial, automotive, and computing applications.
The MAX821 series belongs to Maxim's microprocessor supervisory product line, engineered specifically for deterministic power-on and brownout reset generation in space-constrained, low-power embedded systems.
FAQ
What is the exact reset threshold voltage for MAX821MUS+T and how is it specified?
The MAX821MUS+T has a nominal reset threshold of 4.38V, with guaranteed limits of 4.31V (min) and 4.45V (max) over the full -40°C to +125°C temperature range. This value is laser-trimmed at wafer test and specified in the Electrical Characteristics table under "VTH Reset Threshold" with ±1.5% tolerance. The threshold remains stable with 30ppm/°C tempco, ensuring predictable behavior across operating conditions.
How does the SRT pin configure the reset timeout on MAX821MUS+T?
The SRT pin on MAX821MUS+T selects one of three reset timeout modes: connect to GND for 1ms (maximum), connect to VCC for 20ms (minimum), or leave unconnected for 100ms (minimum). Capacitive loading on SRT must stay below 200pF when left open to avoid unintended faster timeout selection. The internal timer begins counting only after VCC rises above the 4.38V threshold.
Is MAX821MUS+T compatible with systems where VCC drops below 1V during shutdown?
Yes - the MAX821MUS+T guarantees that its active-low RESET output remains valid (driven low) down to VCC = 1V. Below 1V, the output transitions to high-impedance; for applications requiring RESET validity down to 0V, a 100kΩ pull-down resistor on the RESET pin is recommended per Maxim's application guidance to prevent floating logic states.
What is the supply current consumption of MAX821MUS+T and how does it vary with temperature?
The MAX821MUS+T draws 2.5µA typical supply current at +25°C, with maximum 7.0µA over -40°C to +125°C. Typical operating characteristics show normalized supply current varies less than ±10% across temperature, confirming stable ultra-low power operation essential for battery longevity in portable equipment using MAX821MUS+T.
Can MAX821MUS+T interface directly with µPs having bidirectional reset pins?
No - direct connection to µPs with bidirectional reset I/O (e.g., Motorola 68HC11) risks contention. Maxim recommends inserting a 4.7kΩ series resistor between the MAX821MUS+T RESET output and the µP reset pin to isolate drive sources. Additional buffering may be needed for fan-out to other system components, as outlined in Figure 3 of the MAX821/MAX822 datasheet.
MAX821MUS+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:
- 4.38V
- 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
MAX821MUS+T FAQ
1.How can I place an order for MAX821MUS+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX821MUS+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 MAX821MUS+T reliable?
The price and inventory of MAX821MUS+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX821MUS+T is usually 5 days.
3.What payment methods are accepted for MAX821MUS+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX821MUS+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX821MUS+T?
MAX821MUS+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX821MUS+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 MAX821MUS+T?
For technical support, including MAX821MUS+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX821MUS+T requirements.
6.How does Aetrix verify that MAX821MUS+T is sourced from the original manufacturer or authorized distributors?
All MAX821MUS+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 MAX821MUS+T meets industry standards.
7.What is the process for return or replacement of MAX821MUS+T?
All MAX821MUS+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX821MUS+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 MAX821MUS+T part is unused and in its original packaging.
Return procedure for MAX821MUS+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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