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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 SUPERVISOR MPU VOLT MONITOR
- Quantity:
- Payment:
- Shipping:
Inventory:3,158
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Product details
Overview
MAX821RUS-T from Maxim Integrated is an active-low microprocessor supervisory IC that monitors +2.63V supply rails and asserts a reset signal during power-up, brownout, or power-down events. It features pin-selectable reset timeout delays (1ms max / 20ms min / 100ms min), 2.5µA quiescent current, guaranteed RESET validity down to VCC = 1V, and operates across –40°C to +125°C for industrial and automotive power monitoring.
For engineers reviewing the MAX821RUS-T datasheet, MAX821RUS-T pinout, MAX821RUS-T application, or MAX821RUS-T equivalent, this device serves as a precision voltage monitor for critical µP reset control in portable, battery-powered, and high-reliability embedded systems where supply rail stability and deterministic reset timing are essential.
Technical Context
The MAX821RUS-T implements a dedicated voltage-comparator-based reset generator with hysteresis-immune threshold detection and an internal timer synchronized to VCC transitions. Its reset assertion logic is triggered only when VCC falls below the 2.63V nominal threshold (±1.5% over temperature), and it ignores transients ≤12µs at 100mV overdrive.
Reset timeout is configured solely via the SRT pin: grounded for 1ms (max), tied to VCC for 20ms (min), or left floating (<200pF loading) for 100ms (min). The active-low RESET output remains valid and actively driven down to VCC = 1V, enabling robust reset signaling even during deep brownout conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.63V nominal (±1.5% over –40°C to +125°C); ensures reliable assertion before downstream ICs drop out of spec. |
| Supply Current | 2.5µA typical at +25°C; enables multi-year operation in coin-cell–powered devices without compromising reset integrity. |
| Reset Timeout Options | 1ms (max), 20ms (min), or 100ms (min) - selected by SRT pin state; supports fast-boot microcontrollers and legacy systems requiring extended hold times. |
| Operating Temperature | –40°C to +125°C; qualified for under-hood automotive, industrial PLC, and harsh-environment sensor nodes. |
| VCC Validity Range | RESET output guaranteed functional down to VCC = 1V; prevents undefined logic states during gradual power collapse. |
| Transient Immunity | Rejects VCC glitches ≤12µs wide when dipping 100mV below threshold; eliminates false resets from switching noise or ESD coupling. |
Pinout & Package
SOT-143 (4-pin, 1.3mm × 2.1mm, 0.95mm height), leaded package with exposed pad not electrically connected. RoHS-compliant version available as MAX821RUS+T.
| 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; sinks ≥1.2mA at VTH(MIN); requires external pull-up for µP interface compatibility. |
| 3 SRT | Set Reset Timeout input | Three-state logic input: GND → 1ms, VCC → 20ms, open → 100ms; capacitive loading <200pF required for reliable 100ms mode. |
| 4 VCC | Supply voltage input | Monitored rail input (2.7V to 5.5V); powers internal circuitry and defines reset threshold reference point. |
Key Features
| Feature | Design Value |
|---|---|
| Pin-selectable reset timeout | Hardware-configurable delay (1/20/100ms) eliminates need for external RC networks or firmware calibration. |
| Precision 2.63V threshold | Tight ±1.5% tolerance over full temperature range ensures consistent reset assertion across environmental stress. |
| Ultra-low 2.5µA supply current | Enables integration into always-on, energy-harvesting, or battery-backed systems without measurable drain impact. |
| VCC = 1V RESET validity | Guaranteed active drive capability down to 1V allows deterministic reset signaling during deep brownout recovery. |
| Transient-immune comparator | Rejects sub-12µs supply glitches, preventing spurious resets in noisy DC-DC or motor-drive environments. |
Applications
| Industrial PLC Power Monitoring | Automotive Body Control Module |
|---|---|
|
Use Scenario: Monitors 3.3V auxiliary rail powering CAN transceivers and I/O expanders in programmable logic controllers. IC Role / Device Role / Timing Role: Voltage supervisor asserting active-low reset to ARM Cortex-M7 MCU during undervoltage lockout. Use Value: Prevents corrupted register writes and flash corruption during line-sag events with guaranteed 20ms hold time after VCC recovery. |
Use Scenario: Supervises 2.63V LDO output feeding microcontroller watchdog and safety-critical sensors in door module ECUs. IC Role / Device Role / Timing Role: Dedicated reset generator with 100ms timeout ensuring full initialization before CAN bus arbitration begins. Use Value: Eliminates race conditions between power stabilization and firmware boot sequence in ASIL-B compliant subsystems. |
| Portable Medical Sensor Node | Smart Meter Battery Backup Circuit |
|
Use Scenario: Watches coin-cell–supplied 2.63V rail in wearable ECG patch during cold-start and low-battery shutdown. IC Role / Device Role / Timing Role: Low-current supervisor triggering graceful shutdown and memory save via active-low RESET to ultra-low-power MCU. Use Value: 2.5µA ICC extends shelf life >5 years; 1V RESET validity ensures last-data integrity during final discharge phase. |
Use Scenario: Monitors supercapacitor-backed 2.63V rail maintaining RTC and tamper-detection logic during main AC failure. IC Role / Device Role / Timing Role: Brownout detector holding meter SoC in reset until backup voltage stabilizes above 2.63V threshold. Use Value: Pin-selectable 1ms timeout enables rapid resumption of metrology functions post-failure, minimizing billing gap. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage monitor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX822RUS-T | Identical pinout and package; active-high RESET output instead of active-low. | Requires inverted reset logic on host µP or external inverter; unsuitable for systems with dedicated active-low reset inputs. | Select MAX822RUS-T only when µP reset pin is active-high or system-level logic accommodates polarity inversion. |
| TPS3808G12DBVR | 2.63V threshold, but fixed 200ms timeout; 1.6µA ICC; SOT-23-5 package with manual reset input. | Lacks pin-selectable timeout; adds manual reset functionality; larger footprint and different pin count preclude direct layout reuse. | Choose TPS3808G12DBVR when longer, fixed timeout is acceptable and manual reset capability is required for field service. |
Compared with MAX822RUS-T, the MAX821RUS-T provides native active-low reset signaling without level-shifting overhead; compared with TPS3808G12DBVR, it offers hardware-selectable timeout modes in a smaller 4-pin SOT-143 footprint but omits manual reset functionality.
Availability
MAX821RUS-T is available at Aetrix Electronics and suitable for industrial PLC power monitoring, automotive body control modules, and portable medical sensor nodes requiring stable component supply with long-term manufacturability and temperature-grade assurance.
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 precision analog and mixed-signal ICs for power, sensing, and connectivity applications, with emphasis on reliability and integration for demanding environments.
The MAX821/MAX822 product line delivers compact, low-power supervisory circuits optimized for deterministic reset generation in µP-based systems operating across extended industrial and automotive temperature ranges.
FAQ
What is the exact reset threshold voltage for MAX821RUS-T?
The MAX821RUS-T has a nominal reset threshold of 2.63V, with guaranteed tolerance of ±1.5% over the full operating temperature range (–40°C to +125°C). This value is laser-trimmed at wafer test and confirmed in the Electrical Characteristics table of the MAX821/MAX822 datasheet (Rev 3, 2006). The MAX821RUS-T variant is specifically binned and marked for this threshold.
How does the SRT pin configure the reset timeout on MAX821RUS-T?
On the MAX821RUS-T, the SRT pin selects reset timeout duration: connect to GND for 1ms (maximum), tie to VCC for 20ms (minimum), or leave unconnected (with <200pF parasitic capacitance) for 100ms (minimum). This configuration occurs at power-up and remains static; no dynamic reconfiguration is supported. The internal timer starts only after VCC rises above the 2.63V threshold.
Is MAX821RUS-T compatible with 3.3V and 5V systems?
Yes - the MAX821RUS-T operates with VCC from 2.7V to 5.5V and monitors its own supply rail. Its 2.63V threshold is designed for use with 3V-class systems (e.g., 3.3V LDOs with dropout margin) and is also applicable in 5V systems where a dedicated 2.63V reference rail is generated. It does not monitor external voltages; only VCC is sensed.
Does MAX821RUS-T require external components for basic operation?
No - the MAX821RUS-T requires no external resistors, capacitors, or diodes for core supervision functionality. Only a 0.1µF bypass capacitor on VCC (recommended per datasheet Figure 1) and an external pull-up resistor on the open-drain RESET pin are needed for robust operation. The SRT pin may require a pull-down or pull-up resistor if actively driven, but floating is valid for 100ms mode.
What is the minimum VCC level at which MAX821RUS-T guarantees RESET output validity?
The MAX821RUS-T guarantees that its active-low RESET output remains a valid logic low (sinking ≥1.2mA) down to VCC = 1V. Below 1V, the output enters high-impedance state. This specification is explicitly tested and guaranteed across –40°C to +125°C, making MAX821RUS-T suitable for applications requiring reset assertion during deep brownout recovery.
MAX821RUS-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:
- Power Supply Monitor
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 2.63V
- Output:
- -
- Reset:
- Active Low
- Reset Timeout:
- 100ms Minimum
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-4
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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