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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 MPU VOLT MONITOR
- Quantity:
- Payment:
- Shipping:
Inventory:10,000
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Product details
Overview
MAX821UUS-T from Maxim Integrated is an active-low microprocessor supervisory IC that monitors +3V to +5V power supplies and asserts a reset signal when VCC falls below 2.78V, maintaining reset for a pin-selectable timeout (1ms max, 20ms min, or 100ms min) after VCC recovers. It operates from -40°C to +125°C with 2.5µA supply current and guarantees RESET validity down to VCC = 1V. It is used in portable battery-powered equipment requiring reliable power-on reset.
For engineers reviewing the MAX821UUS-T datasheet, MAX821UUS-T pinout, MAX821UUS-T application, or MAX821UUS-T equivalent, this page delivers verified specifications, SOT143 package details, temperature-stable reset threshold accuracy (±1.5% over -40°C to +125°C), transient immunity against VCC glitches ≤12µs at 100mV overdrive, and design guidance for interfacing with bidirectional µP reset pins.
Technical Context
The MAX821UUS-T implements a precision bandgap-based voltage comparator with internal hysteresis and a digital timeout timer controlled by the SRT pin state (GND/VCC/unconnected). Its reset assertion logic is asynchronous to VCC transitions and immune to fast transients due to built-in filtering and comparator overdrive tolerance.
It features guaranteed monotonic reset behavior across full temperature range, with reset threshold tempco of 30ppm/°C and power-down reset delay under 50µs (typical) when VCC falls at 1mV/µs - enabling robust brownout detection in embedded controllers and intelligent instruments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.78V nominal; ensures reset assertion before downstream logic (e.g., 3V µCs) drops below minimum operating voltage. |
| Supply Current | 2.5µA typical at +25°C; enables multi-year battery life in portable barcode scanners and handheld devices. |
| Operating Temp | -40°C to +125°C; supports industrial and automotive under-hood applications without derating. |
| Reset Timeout Options | 1ms (max), 20ms (min), or 100ms (min); selected via SRT pin connection - no external timing components required. |
| VCC Validity Range | RESET guaranteed low for VCC ≥1V; allows clean reset assertion even during deep brownout or partial power collapse. |
| Transient Immunity | Rejects VCC glitches ≤12µs wide at 100mV below threshold; prevents spurious resets in noisy power environments. |
| Reset Threshold Tempco | 30ppm/°C; maintains ±1.5% threshold stability over full temperature range - critical for high-reliability systems. |
Pinout & Package
SOT143-4 surface-mount package (3.0mm × 1.5mm × 1.0mm height), lead-free compatible, rated for reflow soldering per JEDEC J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 GND | Ground reference | Return path for internal comparator and output driver; must be low-impedance connection to system ground plane. |
| 2 RESET | Active-low reset output | Open-drain output asserted low during reset; requires external pull-up for µP interface; sinks ≥1.2mA at VTH(MIN). |
| 3 SRT | Set Reset Timeout input | Digital control pin: GND = 1ms timeout, VCC = 20ms timeout, unconnected = 100ms timeout; <200pF loading required for 100ms mode. |
| 4 VCC | Supply voltage input | Accepts +2.7V to +5.5V; powers internal circuitry and defines reset threshold reference point. |
Key Features
| Feature | Design Value |
|---|---|
| Pin-selectable reset timeout | Three discrete delay options (1ms/20ms/100ms) implemented with single resistor-free SRT connection - eliminates BOM cost and layout complexity. |
| Precision voltage monitoring | 2.78V threshold with ±1.5% tolerance over -40°C to +125°C - ensures deterministic reset timing across environmental extremes. |
| Ultra-low quiescent current | 2.5µA typical supply current - extends battery runtime in always-on portable instrumentation without compromising supervision integrity. |
| Brownout resilience | Internal timer resets on every VCC dip below threshold, guaranteeing reset reassertion during sustained undervoltage - prevents lockup in unstable power conditions. |
| VCC transient immunity | Designed to ignore negative-going VCC glitches ≤12µs at 100mV overdrive - avoids false resets in electrically noisy systems like motor-driven controllers. |
Applications
| Bar-Code Scanners | Portable/Battery-Powered Equipment |
|---|---|
Use Scenario: Handheld scanner powered by single Li-ion cell with dynamic load switching causing VCC sags during laser activation. IC Role / Device Role / Timing Role: Supervisory IC asserting active-low reset to ARM Cortex-M0 host MCU during brownout events. Use Value: Prevents firmware corruption by ensuring MCU remains held in reset until VCC stabilizes above 2.78V and sustains for ≥20ms post-recovery. | Use Scenario: Wireless sensor node operating on coin-cell battery with intermittent RF transmission causing supply droop. IC Role / Device Role / Timing Role: Voltage monitor providing power-on reset and brownout protection for ultra-low-power MSP430 microcontroller. Use Value: 2.5µA supply current minimizes standby drain while guaranteeing valid RESET output down to VCC = 1V - enabling safe shutdown sequencing. |
| Intelligent Instruments | Critical µP and µC Power Monitoring |
Use Scenario: Portable multimeter with auto-ranging analog front-end and LCD display drawing pulsed current. IC Role / Device Role / Timing Role: Reset supervisor ensuring consistent boot initialization of PIC18F microcontroller after battery insertion or cold start. Use Value: Pin-selectable 100ms timeout accommodates slow-rising LDO outputs, eliminating need for external RC timing networks. | Use Scenario: Industrial PLC module with redundant 3.3V supply rails where failure of one rail must trigger controlled processor halt. IC Role / Device Role / Timing Role: Precision voltage monitor detecting undervoltage on primary 3.3V rail and asserting reset to prevent erratic execution. Use Value: 30ppm/°C tempco and -40°C to +125°C operation ensure stable threshold across thermal cycling in enclosed enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX822UUS-T | Identical pinout, package, and threshold (2.78V), but features active-high RESET output instead of active-low. | Requires inverted reset logic on µP side; unsuitable for systems with dedicated active-low reset inputs. | Select MAX822UUS-T only when target microcontroller accepts active-high reset assertion or level-shifting is already present. |
| TPS3123QDBVRQ1 | Automotive-grade (AEC-Q100), 2.73V threshold, fixed 200ms timeout, higher 8µA ICC, SOT-23-5 package. | Designed for automotive infotainment and ADAS; lacks pin-selectable timeout and SOT143 footprint compatibility. | Choose TPS3123QDBVRQ1 only for AEC-Q100-compliant designs requiring extended qualification - not a drop-in replacement. |
Compared with MAX822UUS-T, the MAX821UUS-T provides native active-low reset signaling without external inversion, while TPS3123QDBVRQ1 adds automotive qualification at the cost of fixed timing and larger package - making MAX821UUS-T optimal for space-constrained industrial portable designs needing flexible timeout and minimal current draw.
Availability
MAX821UUS-T is available at Aetrix Electronics and suitable for portable/battery-powered equipment, intelligent instruments, bar-code scanners, and critical µP power monitoring requiring stable component supply across extended temperature ranges and long production lifecycles.
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) is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and computing markets.
The MAX821/MAX822 product line was designed specifically for cost-sensitive, space-constrained embedded systems requiring reliable, low-power voltage supervision with programmable reset timing - targeting portable instrumentation and industrial controllers.
FAQ
What is the exact reset threshold voltage of the MAX821UUS-T?
The MAX821UUS-T has a nominal reset threshold voltage of 2.78V, with guaranteed limits of 2.74V (min) and 2.81V (max) over the full operating temperature range (-40°C to +125°C). This value is factory-trimmed and specified in the Electrical Characteristics table of the official datasheet (Rev 3, 19-1122).
Does the MAX821UUS-T support operation down to 1V supply voltage?
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 RESET validity down to 0V, a 100kΩ pull-down resistor on the RESET pin is recommended per the datasheet's Figure 2a.
How is the reset timeout delay configured on the MAX821UUS-T?
The reset timeout delay on the MAX821UUS-T is set via the SRT pin: connect SRT to GND for 1ms (maximum) delay, connect SRT to VCC for 20ms (minimum) delay, or leave SRT unconnected for 100ms (minimum) delay. Capacitive loading on SRT must remain below 200pF to ensure correct 100ms operation.
Can the MAX821UUS-T be used with a 3.3V microcontroller?
Yes - the MAX821UUS-T is explicitly designed for +3V to +5V power-supply monitoring and is fully compatible with 3.3V systems. Its 2.78V reset threshold ensures assertion before most 3.3V µCs fall below their 2.97V minimum operating voltage, providing safe margin for brownout detection.
What package type does the MAX821UUS-T use, and is it RoHS compliant?
The MAX821UUS-T uses the SOT143-4 package (3.0mm × 1.5mm footprint, 1.0mm height) with lead-free termination. The "-T" suffix indicates tape-and-reel packaging; RoHS compliance is achieved with the "+T" variant (MAX821UUS+T), while MAX821UUS-T is leaded but meets JEDEC reflow standards.
MAX821UUS-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:
- 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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