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Analog Devices Inc./Maxim Integrated MAX821PUS-T
- Part No.:
- MAX821PUS-T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- TO-253-4, TO-253AA
- Datasheet:
-
MAX821PUS-T.pdf
- Description:
- IC SUPERVISOR MPU VOLT MONITOR
- Quantity:
- Payment:
- Shipping:
Inventory:4,259
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Product details
Overview
MAX821PUS-T from Maxim Integrated is an active-low microprocessor supervisory IC in SOT-143-4 package, designed to monitor +4.00V nominal supply voltage and assert a guaranteed logic-low RESET output down to VCC = 1V. It provides pin-selectable power-on reset timeout delays of 1ms (max), 20ms (min), or 100ms (min) and draws only 2.5µA supply current. It is used in portable/battery-powered equipment for reliable power-up sequencing and brownout protection.
For engineers reviewing the MAX821PUS-T datasheet, MAX821PUS-T pinout, MAX821PUS-T application, or MAX821PUS-T equivalent, key selection criteria include its 4.00V reset threshold, SRT-pin programmable timeout, guaranteed RESET validity at VCC ≥ 1V, low 2.5µA quiescent current, and operation across –40°C to +125°C.
Technical Context
The MAX821PUS-T implements a precision voltage comparator with 30ppm/°C tempco and internal timer architecture triggered by VCC crossing the 4.00V threshold. Its SRT input directly selects one of three discrete timeout modes without external components.
Reset assertion is immune to fast transients (e.g., ≤12µs negative glitches at 100mV overdrive), and the RESET output remains valid during VCC decay down to 1V-critical for systems requiring deterministic behavior during deep brownout conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 4.00V nominal; ensures reset assertion before downstream logic (e.g., 5V µP) exits valid operating range. |
| Supply Current | 2.5µA typical; enables multi-year battery life in always-on portable instrumentation. |
| Operating Temp | –40°C to +125°C; supports industrial and automotive under-hood applications without derating. |
| Reset Timeout | PIN-selectable: 1ms (max), 20ms (min), or 100ms (min); eliminates need for external RC timing networks. |
| VCC Validity | RESET guaranteed low for VCC ≥ 1V; ensures controlled reset state even during severe undervoltage events. |
| Package | SOT-143-4; 1.3mm × 2.1mm footprint ideal for space-constrained handheld devices. |
| Transient Immunity | Rejects ≤12µs VCC glitches at 100mV overdrive; prevents spurious resets in noisy power environments. |
Pinout & Package
SOT-143-4 surface-mount package with 1.3mm × 2.1mm body, 0.95mm height, and gull-wing leads. RoHS-compliant, leaded variant (–T suffix).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 GND | Ground reference | Low-impedance return path for internal comparator and timer; must be connected directly to system ground plane. |
| 2 RESET | Active-low reset output | Open-drain output pulled low during reset condition; requires external pull-up for µP interface compatibility. |
| 3 SRT | Set Reset Timeout input | Three-state control: GND = 1ms max, VCC = 20ms min, open = 100ms min; capacitive loading <200pF required for open mode. |
| 4 VCC | Supply voltage input | Power input for internal circuitry; accepts 1.0V to 5.5V; decoupling capacitor recommended near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Pin-selectable reset timeout | Eliminates external timing components and PCB layout variability for 1ms/20ms/100ms delay selection. |
| 4.00V precision reset threshold | Matches standard 4.0V LDO outputs and 5V-system brownout margins with ±1.5% accuracy over temperature. |
| 2.5µA supply current | Reduces standby power in battery-backed systems-e.g., extends CR2032 life beyond 10 years in low-duty-cycle sensors. |
| VCC = 1V RESET validity | Ensures deterministic reset state during deep brownout, preventing µP lockup or undefined execution. |
| Transient-immune comparator | Rejects short-duration supply noise without requiring additional filtering, simplifying front-end design. |
Applications
| Bar-Code Scanners | Portable Medical Devices |
|---|---|
Use Scenario: Handheld scanner powers up from cold start with alkaline batteries dropping from 4.5V to 3.2V during discharge. IC Role / Device Role / Timing Role: Supervisory IC monitors VCC and asserts RESET until stable 4.00V is confirmed, then holds reset for 20ms to allow crystal oscillator stabilization. Use Value: Prevents firmware crash during marginal battery operation by enforcing minimum power-up timing and voltage margin. | Use Scenario: Battery-powered glucose meter operates intermittently with long sleep periods between measurements. IC Role / Device Role / Timing Role: Provides ultra-low-current (2.5µA) supervision during sleep; triggers clean reset on wake-up if VCC dips below 4.00V due to load transient. Use Value: Enables >5-year battery life while guaranteeing safe boot sequence after every power cycle. |
| Industrial PLC I/O Modules | Automotive Body Control Units |
Use Scenario: Module experiences 12V battery droop to 6V during cranking, followed by rapid recovery. IC Role / Device Role / Timing Role: Detects VCC fall below 4.00V and asserts RESET; maintains reset for 100ms after recovery to ensure full MCU initialization. Use Value: Avoids partial initialization and communication faults during engine start by enforcing robust power-good window. | Use Scenario: BCM powers from vehicle battery subject to load dump and cold-crank transients. IC Role / Device Role / Timing Role: Monitors 5V rail derived from DC-DC converter; ignores ≤12µs supply glitches but asserts reset on sustained brownout. Use Value: Increases system reliability by eliminating false resets during normal electrical noise, reducing warranty claims. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage supervisor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX822PUS-T | Active-high RESET output; identical 4.00V threshold, timeout options, and specs otherwise. | Requires inverted reset logic on µP side; unsuitable where hardware reset polarity is fixed. | Select when host µP accepts active-high reset or level-shifting is already present. |
| TPS3808G33DBVR | Fixed 3.3V threshold; 200ms default timeout (adjustable via external capacitor); 1.1µA IQ. | Lacks pin-selectable timeout; requires external component for timing; optimized for lower-voltage systems. | Choose for 3.3V systems needing ultra-low IQ, but not for 4.0V monitoring or no-component timeout flexibility. |
Compared with MAX822PUS-T, the MAX821PUS-T provides mandatory active-low reset signaling without logic inversion; compared with TPS3808G33DBVR, it delivers precise 4.00V detection and zero-component timeout selection-critical for legacy 5V designs and space-constrained layouts.
Availability
MAX821PUS-T is available at Aetrix Electronics and suitable for portable medical devices, industrial PLC I/O modules, and automotive body control units requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.
Supply support for MAX821PUS-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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.
The MAX821/MAX822 product line was designed specifically for cost-sensitive, space-constrained microprocessor systems requiring precision voltage monitoring and flexible, component-free reset timing across extended temperature ranges.
FAQ
What is the exact reset threshold voltage for MAX821PUS-T?
The MAX821PUS-T has a nominal reset threshold of 4.00V, with guaranteed minimum and maximum values of 3.91V and 4.09V respectively over the full –40°C to +125°C temperature range. This value is laser-trimmed during production and documented in the Electrical Characteristics table of the MAX821/MAX822 datasheet (Rev 3, 2006).
How does the SRT pin configure the reset timeout on MAX821PUS-T?
The SRT pin on MAX821PUS-T sets the reset timeout period: 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 left open to avoid unintended timeout selection, per the "Setting the Reset Timeout Delay" section of the datasheet.
Is MAX821PUS-T compatible with 3.3V microcontrollers?
No-MAX821PUS-T is specified for 4.00V threshold monitoring and is intended for use with 5V or 4V nominal supply rails. For 3.3V systems, Maxim offers the MAX821TUS-T (3.08V threshold) or alternatives like the TPS3808G33. Using MAX821PUS-T on a 3.3V rail would cause continuous reset assertion since VCC never reaches 4.00V.
Does MAX821PUS-T require an external pull-up resistor on the RESET pin?
Yes-MAX821PUS-T features an open-drain active-low RESET output and requires an external pull-up resistor (typically 10kΩ to VCC) to establish a valid high state when not asserting reset. The datasheet recommends this for proper interfacing with standard µP reset inputs, especially those with internal weak pull-ups insufficient for noise immunity.
What is the maximum operating temperature rating for MAX821PUS-T?
The MAX821PUS-T is rated for continuous operation from –40°C to +125°C ambient temperature, with all electrical specifications guaranteed across this full industrial/automotive range. This is confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables of the official MAX821/MAX822 datasheet (document 19-1122, Rev 3).
MAX821PUS-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- TO-253-4, TO-253AA
- Packaging:
- Bulk
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Simple Reset/Power-On Reset
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4V
- 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
MAX821PUS-T FAQ
1.How can I place an order for MAX821PUS-T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX821PUS-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 MAX821PUS-T reliable?
The price and inventory of MAX821PUS-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX821PUS-T is usually 5 days.
3.What payment methods are accepted for MAX821PUS-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX821PUS-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX821PUS-T?
MAX821PUS-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX821PUS-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 MAX821PUS-T?
For technical support, including MAX821PUS-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX821PUS-T requirements.
6.How does Aetrix verify that MAX821PUS-T is sourced from the original manufacturer or authorized distributors?
All MAX821PUS-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 MAX821PUS-T meets industry standards.
7.What is the process for return or replacement of MAX821PUS-T?
All MAX821PUS-T units undergo pre-shipment inspection (PSI). If there is an issue with MAX821PUS-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 MAX821PUS-T part is unused and in its original packaging.
Return procedure for MAX821PUS-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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