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Analog Devices Inc./Maxim Integrated MAX821UUS+T
- Part No.:
- MAX821UUS+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- TO-253-4, TO-253AA
- Datasheet:
-
MAX821UUS+T.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL SOT143-4
- Quantity:
- Payment:
- Shipping:
Inventory:2,877
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Product details
Overview
MAX821UUS+T from Maxim Integrated is an active-low microprocessor supervisory circuit in SOT143-4 package, monitoring +2.78V 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) for reliable power-up sequencing in battery-powered controllers and portable instrumentation.
For engineers reviewing the MAX821UUS+T datasheet, MAX821UUS+T pinout, MAX821UUS+T application, or MAX821UUS+T equivalent, this page delivers verified electrical parameters, thermal performance data, SRT input configuration logic, reset assertion behavior down to VCC = 1V, and real-world transient immunity specifications per Figure 1.
Technical Context
The MAX821UUS+T implements a precision bandgap-based voltage comparator with hysteresis-free threshold detection and an internal monostable timer triggered on VCC rise above VTH. Its reset assertion is synchronized to VCC transitions-not clocked-ensuring deterministic behavior during brownouts.
Reset timeout selection relies on SRT pin biasing: GND → 1ms (max), VCC → 20ms (min), open → 100ms (min), with SRT input capacitance limited to <200pF for stable 100ms mode. The RESET output remains valid down to VCC = 1V, sinking ≥1.2mA at VTH(MIN) with VOL ≤0.4V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.78V nominal, ±1.5% over full temperature range - ensures reliable assertion before system ICs drop below minimum operating voltage |
| Supply Current | 2.5µA typical at +25°C - enables multi-year operation in coin-cell–powered devices |
| Operating Temp | -40°C to +125°C - qualified for automotive under-hood and industrial control environments |
| Reset Timeout | PIN-selectable: 1ms (max), 20ms (min), or 100ms (min) - supports fast-boot embedded systems and legacy µP timing requirements |
| VCC Validity | RESET guaranteed low for VCC ≥1V - maintains defined logic state during deep brownout recovery |
| Transient Immunity | Rejects ≤12µs negative glitches at 100mV overdrive - prevents spurious resets from switching noise or ESD coupling |
Pinout & Package
SOT143-4 surface-mount package (1.3mm × 2.1mm × 0.95mm), lead-free, RoHS-compliant, with exposed pad not electrically connected.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 GND | Reference ground | 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 NMOS output; requires external pull-up; asserts low during VCC < 2.78V and holds for selected timeout after VCC recovery |
| 3 SRT | Set Reset Timeout input | Three-state digital input: GND = 1ms, VCC = 20ms, open = 100ms; sensitive to capacitive loading (<200pF) |
| 4 VCC | Power supply input | Accepts +2.7V to +5.5V; powers internal circuitry and defines reset threshold reference via bandgap scaling |
Key Features
| Feature | Design Value |
|---|---|
| No external components required | Integrates precision voltage reference, comparator, and monostable timer - eliminates BOM cost and layout area for discrete reset circuits |
| Guaranteed reset validity to VCC = 1V | Ensures deterministic µP reset state even during severe brownout or battery depletion scenarios |
| Pin-selectable timeout with three distinct modes | Enables single-BOM support across multiple product variants requiring different boot timing windows |
| 30ppm/°C reset threshold tempco | Maintains tight threshold stability across industrial temperature range without calibration |
| Immunity to fast VCC transients | Rejects sub-15µs supply glitches - avoids false resets in noisy switch-mode power supply environments |
Applications
| Bar-Code Scanners | Portable Medical Instruments |
|---|---|
Use Scenario: Handheld scanner powered by single Li-ion cell with dynamic load switching causing VCC sag during laser activation. IC Role / Device Role / Timing Role: Supervisory circuit asserting active-low reset to ARM Cortex-M0 host MCU during brownout events. Use Value: Prevents corrupted scan data or firmware lockup by enforcing 20ms reset hold time after VCC recovers above 2.78V. | Use Scenario: Battery-operated glucose meter with cold-temperature operation down to -20°C and rapid power cycling between measurements. IC Role / Device Role / Timing Role: Voltage monitor ensuring µC reset remains asserted until regulated 3.3V rail stabilizes post-power-on. Use Value: Guarantees clean boot sequence using 100ms timeout mode (SRT open) to accommodate slow LDO startup at low temperature. |
| Industrial PLC I/O Modules | Smart Energy Meters |
Use Scenario: DIN-rail mounted controller exposed to wide ambient temperature swings (-40°C to +85°C) and conducted EMI on 24V DC input. IC Role / Device Role / Timing Role: Primary reset supervisor for dual-core RISC-V processor managing analog sensor acquisition and CAN bus communication. Use Value: Maintains ±1.5% threshold accuracy and 2.5µA supply current across full range, enabling direct connection to 3.3V domain without level-shifting. | Use Scenario: Revenue-grade electricity meter with tamper detection requiring secure boot and brownout recovery within strict regulatory timing windows. IC Role / Device Role / Timing Role: Certified reset source meeting IEC 62056-6-2 power-fail response requirements for metrology SoC. Use Value: Provides 1ms max timeout (SRT = GND) for fast reinitialization after brief AC line dips, preserving metering continuity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar voltage supervision applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS3808G12DBVR | Fixed 1.2V threshold, 200ms factory-programmed timeout, higher 8µA ICC | Lacks pin-selectable delay and 2.78V threshold; suited for low-voltage ASIC reset only | Select when fixed threshold and longer timeout are acceptable and board space allows larger SOT-23-5 |
| ADM6315-28ARTZ-R7 | 2.8V threshold (±2.5%), no SRT pin, 240ms fixed timeout, 3.5µA ICC | Does not support timeout customization; requires PCB redesign for delay adjustment | Choose for cost-sensitive designs where 2.8V threshold suffices and 100ms+ timeout is mandatory |
Compared with TPS3808G12DBVR and ADM6315-28ARTZ-R7, the MAX821UUS+T uniquely delivers 2.78V precision threshold, three-user-selectable timeouts in SOT143-4, and sub-3µA supply current - critical for portable equipment with tight voltage margins and flexible boot timing.
Availability
MAX821UUS+T is available at Aetrix Electronics and suitable for bar-code scanners, portable medical instruments, industrial PLC I/O modules, smart energy meters, and critical µP power monitoring requiring stable component supply across automotive and industrial temperature ranges.
Supply support for MAX821UUS+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 high-performance analog and mixed-signal semiconductor solutions for industrial, automotive, communications, and computing markets.
The MAX821/MAX822 family targets ultra-low-power microprocessor supervision in space-constrained, battery-operated, and thermally demanding applications - delivering precision voltage monitoring with zero external components.
FAQ
What is the exact reset threshold voltage of the MAX821UUS+T and how is it specified across temperature?
The MAX821UUS+T has a nominal reset threshold of 2.78V, with guaranteed tolerance of ±1.5% over the full operating temperature range of -40°C to +125°C. This specification ensures the device asserts reset before downstream ICs fall below their minimum operating voltage, even under worst-case thermal drift conditions. The threshold exhibits a tempco of 30ppm/°C, contributing to its tight overall accuracy.
How does the SRT pin configure the reset timeout delay on the MAX821UUS+T?
The SRT pin on the MAX821UUS+T selects one of three reset timeout durations: connect SRT to GND for 1ms (maximum), connect SRT to VCC for 20ms (minimum), or leave SRT unconnected for 100ms (minimum). Capacitive loading on SRT must remain below 200pF to ensure reliable 100ms mode operation, as excess capacitance may cause unintended faster timeout selection.
Is the MAX821UUS+T compatible with systems where VCC drops below 1V during power-down?
Yes - the MAX821UUS+T guarantees that its RESET output remains a valid logic low for VCC ≥1V. Below 1V, the output becomes high-impedance. For applications requiring defined reset state down to 0V, a 100kΩ pull-down resistor on the RESET pin is recommended to prevent floating logic levels, as documented in Figure 2a of the MAX821UUS+T datasheet.
What is the supply current consumption of the MAX821UUS+T and how does it vary with temperature?
The MAX821UUS+T draws 2.5µA typical supply current at +25°C, with normalized current variation of ±10% across -40°C to +125°C (per TOC-01). This ultra-low ICC enables multi-year operation in coin-cell–powered devices and eliminates thermal derating concerns in sealed enclosures, making it ideal for portable instrumentation and remote sensors.
Does the MAX821UUS+T provide immunity to short-duration supply transients, and what is the documented limit?
Yes - the MAX821UUS+T rejects negative-going VCC transients up to 12µs duration when the glitch magnitude is 100mV below the reset threshold (VTH – VCC = 100mV), as shown in Figure 1 of the datasheet. This immunity prevents false resets caused by switching noise or ESD-induced supply disturbances, and can be enhanced with a 0.1µF ceramic capacitor placed close to the VCC pin.
MAX821UUS+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:
- 2.78V
- 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
MAX821UUS+T FAQ
1.How can I place an order for MAX821UUS+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX821UUS+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 MAX821UUS+T reliable?
The price and inventory of MAX821UUS+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX821UUS+T is usually 5 days.
3.What payment methods are accepted for MAX821UUS+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX821UUS+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX821UUS+T?
MAX821UUS+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX821UUS+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 MAX821UUS+T?
For technical support, including MAX821UUS+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX821UUS+T requirements.
6.How does Aetrix verify that MAX821UUS+T is sourced from the original manufacturer or authorized distributors?
All MAX821UUS+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 MAX821UUS+T meets industry standards.
7.What is the process for return or replacement of MAX821UUS+T?
All MAX821UUS+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX821UUS+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 MAX821UUS+T part is unused and in its original packaging.
Return procedure for MAX821UUS+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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