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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 MPU VOLT MONITOR
- Quantity:
- Payment:
- Shipping:
Inventory:4,514
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Product details
Overview
MAX821LUS-T from Maxim Integrated is an active-low microprocessor supervisory IC that monitors +4.38V supply voltage, asserts a guaranteed logic-low RESET output down to VCC = 1V, and provides pin-selectable power-on reset timeout delays of 1ms (max), 20ms (min), or 100ms (min) in a 4-pin SOT143 package for embedded power monitoring in portable and industrial systems.
For engineers reviewing the MAX821LUS-T datasheet, MAX821LUS-T pinout, MAX821LUS-T application, or MAX821LUS-T equivalent, this device delivers precision voltage supervision with transient immunity, ultra-low 2.5µA supply current, and guaranteed operation across –40°C to +125°C - critical for reliable µP reset sequencing in battery-powered and harsh-environment designs.
Technical Context
The MAX821LUS-T implements a dedicated voltage-monitoring comparator with hysteresis and an internal timer controlled by the SRT pin. Its reset threshold is fixed at 4.38V (nominal), with ±30ppm/°C tempco and guaranteed accuracy over full temperature range.
It features active-low open-drain RESET output with VOL ≤0.4V at ISINK = 3.2mA (VCC = VTH(MIN)), and supports three discrete timeout modes via SRT pin state: GND (1ms max), VCC (20ms min), or unconnected (100ms min), with <200pF SRT capacitance requirement for stable 100ms selection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 4.38V nominal - precisely matches +5V system rails with margin above typical regulator dropout. |
| Supply Current | 2.5µA typical - enables multi-year battery life in always-on portable equipment. |
| Operating Temp | –40°C to +125°C - qualified for automotive under-hood and industrial control environments. |
| RESET Output | Active-low, open-drain - compatible with standard µP reset inputs and allows wired-OR configuration. |
| Reset Timeout | PIN-selectable: 1ms (max), 20ms (min), or 100ms (min) - eliminates external RC timing components. |
| VCC Validity | RESET guaranteed low down to VCC = 1V - ensures deterministic reset assertion during deep brownout. |
| Transient Immunity | Rejects <12µs negative VCC glitches ≥100mV below threshold - prevents false resets from noise. |
Pinout & Package
SOT143-4 surface-mount package (3.0mm × 1.6mm × 1.1mm), leaded, with exposed pad not electrically connected. RoHS-compliant version available as MAX821LUS+T.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 GND | Ground reference | Return path for internal comparator and output stage; must be low-impedance connection to system ground plane. |
| 2 RESET | Active-low reset output | Open-drain output asserted low during VCC undervoltage or timeout; requires external pull-up for logic-high state. |
| 3 SRT | Set Reset Timeout input | Three-state control: GND = 1ms max delay, VCC = 20ms min delay, open = 100ms min delay; <200pF loading required for open mode. |
| 4 VCC | Supply voltage input | Monitored +4.38V rail; powers internal circuitry and defines reset threshold reference point. |
Key Features
| Feature | Design Value |
|---|---|
| Pin-selectable reset timeout | Eliminates external timing resistors/capacitors and reduces BOM count by one component. |
| Guaranteed RESET down to VCC = 1V | Ensures valid reset signal throughout full power-rail collapse - no undefined logic states during brownout. |
| 2.5µA supply current | Reduces quiescent power consumption by >90% vs. legacy reset ICs, extending battery runtime significantly. |
| –40°C to +125°C operation | Validates functionality across full industrial and extended automotive temperature ranges without derating. |
| VCC transient immunity | Prevents spurious resets from EMI or switching noise, improving system robustness in noisy power environments. |
Applications
| Portable Medical Devices | Industrial PLC Controllers |
|---|---|
Use Scenario: Battery-powered glucose meters and handheld diagnostic tools requiring long shelf life and reliable cold-start behavior. IC Role / Device Role / Timing Role: Voltage supervisor asserting active-low reset until regulated +4.38V rail stabilizes post-battery insertion. Use Value: 2.5µA quiescent current extends shelf life beyond 5 years; 100ms timeout ensures complete µP initialization before firmware execution. |
Use Scenario: DIN-rail mounted programmable logic controllers operating in factory-floor environments with wide ambient temperature swings. IC Role / Device Role / Timing Role: Primary reset source for ARM-based controller SoC, monitoring 5V backplane supply with immunity to motor-drive-induced transients. Use Value: –40°C to +125°C rating guarantees operation without thermal derating; 12µs glitch rejection prevents false resets during contactor switching. |
| Barcode Scanner Handhelds | Automotive Body Control Modules |
Use Scenario: Ruggedized handheld scanners used in warehouse logistics with frequent on/off cycling and vibration exposure. IC Role / Device Role / Timing Role: Supervises 5V DC-DC output powering image sensor and decode engine, using 1ms timeout for rapid wake-up. Use Value: Pin-selectable 1ms max delay enables sub-10ms boot time; SOT143 footprint minimizes PCB area in space-constrained housing. |
Use Scenario: Low-voltage body electronics modules powered from vehicle battery (9V–16V) with LDO-regulated 5V domain. IC Role / Device Role / Timing Role: Monitors post-LDO 4.38V rail to ensure clean reset during ignition cycling and load-dump events. Use Value: Guaranteed RESET validity down to VCC = 1V prevents latch-up during cranking; 20ms timeout aligns with CAN bus initialization timing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX822LUS-T | Identical pinout and timing, but active-high RESET output. | Requires redesign of reset logic polarity; incompatible with µPs expecting active-low reset. | Select only when host system reset input is active-high or pull-up/pull-down strategy differs. |
| TPS3808G12DBVR | Fixed 1.2V threshold, 200ms default timeout (adjustable via capacitor), 1.6µA ICC. | Lacks pin-selectable timeout; requires external timing cap; lower supply current but different voltage range. | Choose for ultra-low-power designs needing <2µA ICC, but accept added BOM and layout complexity. |
Compared with MAX822LUS-T, the MAX821LUS-T provides mandatory active-low reset signaling for legacy µPs, while TPS3808G12DBVR trades pin-selectable simplicity for lower current and adjustable timing - making MAX821LUS-T optimal for cost-sensitive, drop-in 4.38V supervision where polarity and zero-component timing are design priorities.
Availability
MAX821LUS-T is available at Aetrix Electronics and suitable for portable medical devices, industrial PLC controllers, barcode scanner handhelds, and automotive body control modules requiring stable component supply with full temperature-range qualification and leaded packaging.
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) is a U.S.-based 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 guaranteed reset assertion during power-up, brownout, and shutdown - with emphasis on eliminating external components and supporting wide-temperature operation.
FAQ
What is the exact reset threshold voltage of the MAX821LUS-T?
The MAX821LUS-T has a nominal reset threshold of 4.38V, with guaranteed minimum and maximum values of 4.31V and 4.45V respectively over the full –40°C to +125°C temperature range. This value is laser-trimmed at wafer test and specified in the Ordering Information table of the datasheet.
How does the SRT pin configure the reset timeout on the MAX821LUS-T?
The SRT pin on the MAX821LUS-T selects reset timeout via three states: connect to GND for 1ms (maximum), connect to VCC for 20ms (minimum), or leave unconnected for 100ms (minimum). The unconnected mode requires SRT pin capacitance <200pF to avoid unintended timeout shortening.
Is the MAX821LUS-T compatible with 3.3V microcontrollers?
No - the MAX821LUS-T is configured for 4.38V threshold and monitors a +5V-derived rail. For 3.3V systems, use MAX821TUS-T (3.08V threshold) or MAX821SUS-T (2.93V threshold); the 'L' suffix explicitly denotes the 4.38V variant and is not voltage-flexible.
Does the MAX821LUS-T require an external pull-up resistor on the RESET pin?
Yes - the MAX821LUS-T features an open-drain active-low RESET output, so an external pull-up resistor (typically 10kΩ to VCC) is required to establish a defined logic-high state when reset is inactive. Without it, the RESET line floats and may cause µP startup failure.
What is the maximum VCC voltage the MAX821LUS-T can withstand?
The MAX821LUS-T has an absolute maximum VCC rating of 6.0V. Operation above this voltage risks permanent damage. The device is intended for monitoring 5V nominal supplies, and its 4.38V threshold provides appropriate margin relative to typical 5V ±5% regulation limits.
MAX821LUS-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:
- 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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