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Analog Devices Inc./Maxim Integrated MAX6821ZUK+
- Part No.:
- MAX6821ZUK+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- SC-74A, SOT-753
- Datasheet:
-
MAX6821ZUK+.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:1,380
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Product details
Overview
MAX6821ZUK+ from Maxim Integrated is a low-voltage microprocessor supervisory IC in 5-pin SOT23 package, featuring +2.32V reset threshold, 140ms minimum reset timeout, 1.6s watchdog timer, push-pull active-low RESET output, and debounced manual reset input - used for reliable power-on/power-down/brownout reset control in embedded controllers and portable equipment.
For engineers reviewing the MAX6821ZUK+ datasheet, MAX6821ZUK+ pinout, MAX6821ZUK+ application, or MAX6821ZUK+ equivalent, this page delivers verified circuit role, exact threshold voltage, watchdog timing, reset output type, manual reset behavior, and real-world deployment context - all confirmed from Maxim's official datasheet Rev 3 (7/14).
Technical Context
The MAX6821ZUK+ integrates voltage monitoring, watchdog timer, and manual reset logic into a single BiCMOS IC. Its reset generator asserts active-low RESET when VCC falls below 2.32V (±0.07V over -40°C to +125°C), holding it asserted for ≥140ms after VCC recovers above threshold. The watchdog monitors WDI transitions and triggers reset if no edge occurs within 1.6s (±0.48s over temperature).
It features internal 50kΩ MR pullup, supports VCC down to +1.0V with guaranteed reset validity, and rejects negative VCC transients ≤20µs at 100mV overdrive. All functions operate without external components and are fully specified across automotive-grade temperature range (-40°C to +125°C).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | +2.32V (±0.07V over -40°C to +125°C); ensures reliable brownout detection for 2.5V/2.3V system rails |
| Reset Timeout Period | 140ms min (200ms typ); guarantees µP remains held in reset long enough for stable power rail recovery |
| Watchdog Timeout | 1.6s nominal (1.12–2.4s over temp); provides robust software execution monitoring for embedded firmware |
| RESET Output Type | Active-low push-pull; drives high/low directly without external pullup, compatible with standard µP reset inputs |
| Supply Current | 25µA max at +125°C (VCC = +3.6V); enables ultra-low-power operation in battery-powered instruments |
| Operating Voltage Range | +1.2V to +5.5V (over full temp); supports valid reset assertion even during deep brownout conditions |
| MR Input Logic | Active-low with 50kΩ internal pullup; eliminates need for external resistor and enables momentary switch interface |
Pinout & Package
Package: 5-pin SOT23-5 (U5-1 outline, land pattern 21-0057), RoHS-compliant, rated for -40°C to +125°C operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | RESET (active-low) | Push-pull output asserting low during VCC undervoltage, MR assertion, or watchdog timeout; drives µP reset pin directly |
| 2 | GND | Ground reference for all internal circuits and reset threshold sensing; must be low-impedance connection |
| 3 | MR (manual reset) | Active-low input with internal 50kΩ pullup to VCC; falling edge initiates reset, held for full 140ms timeout after release |
| 4 | WDI (watchdog input) | Edge-sensitive input; rising or falling edge resets 1.6s watchdog timer; left unconnected disables watchdog |
| 5 | VCC | Power supply and monitored voltage source; reset threshold referenced to this pin; valid down to +1.0V |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed reset validity to VCC = +1.0V | Ensures fail-safe reset assertion even during severe brownout - critical for data integrity in portable equipment |
| No external components required | Reduces BOM count and PCB area; eliminates calibration resistors, capacitors, or discrete timing elements |
| Immunity to short negative VCC transients | Rejects ≤20µs glitches at 100mV overdrive - prevents spurious resets in noisy industrial or automotive environments |
| Debounced manual reset with internal pullup | Enables direct connection of momentary switch to GND; no external RC network or firmware debounce needed |
| 1.6s watchdog with 50ns pulse detection | Supports tight firmware supervision; detects microsecond-level I/O toggles to prevent stuck-loop failures |
Applications
| Set-Top Boxes | Embedded Controllers |
|---|---|
|
Use Scenario: Power sequencing and firmware crash recovery in digital video broadcast receivers. IC Role / Device Role / Timing Role: Supervisory IC providing power-on reset, brownout protection, and watchdog-triggered recovery. Use Value: Prevents corrupted channel tuning or EPG data loss by enforcing clean µP restart after power instability or software hang. |
Use Scenario: Reliable boot initialization and runtime fault recovery in HVAC, PLC, and industrial gateways. IC Role / Device Role / Timing Role: Voltage monitor and watchdog supervisor ensuring deterministic µP startup and continuous firmware health check. Use Value: Eliminates field failures caused by undetected code lockups - maintains communication uptime and control loop integrity. |
| Intelligent Instruments | Portable/Battery-Powered Equipment |
|
Use Scenario: Precision measurement systems requiring stable initialization and glitch-free operation during battery voltage sag. IC Role / Device Role / Timing Role: Low-threshold (+2.32V) supervisor enabling safe operation down to weak battery states while maintaining reset reliability. Use Value: Extends usable battery life by allowing continued function until VCC drops just below 2.32V, then enforcing controlled shutdown/reset. |
Use Scenario: Handheld test meters, medical sensors, and portable data loggers operating from single-cell Li-ion or alkaline sources. IC Role / Device Role / Timing Role: Ultra-low-quiescent-current (25µA max) supervisor with VCC-down-to-1.0V reset guarantee. Use Value: Delivers longest possible runtime before final brownout reset - avoids premature shutdown during transient load spikes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6822ZUK+ | Same +2.32V threshold and 140ms timeout, but open-drain RESET output instead of push-pull | Requires external pullup resistor; suited for bidirectional µP reset pins (e.g., Motorola 68HC11) | Select MAX6822ZUK+ only when interfacing with µPs needing open-drain reset arbitration or wired-OR reset buses |
| TPS3808G18DBVR | +1.8V fixed threshold, 200ms reset timeout, no manual reset input, 1.25µA quiescent current | Lacks MR and watchdog; optimized for ultra-low-power always-on monitoring, not full-feature supervision | Choose TPS3808G18DBVR only for simple voltage monitoring where manual reset and watchdog are unnecessary |
Compared with MAX6821ZUK+, MAX6822ZUK+ offers identical supervision specs but requires external pullup due to open-drain RESET, while TPS3808G18DBVR trades away MR/watchdog capability for lower power and simpler architecture - making MAX6821ZUK+ the only choice when full-feature, self-contained supervision is required.
Availability
MAX6821ZUK+ is available at Aetrix Electronics and suitable for embedded controllers, intelligent instruments, and portable/battery-powered equipment requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.
Supply support for MAX6821ZUK+ 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, mixed-signal, and power management ICs for demanding industrial, computing, and communications applications.
The MAX6821ZUK+ belongs to the MAX6821–MAX6825 family of low-voltage µP supervisors - engineered specifically for reliable reset generation, watchdog monitoring, and manual reset integration in space-constrained, battery-sensitive, and thermally harsh embedded systems.
FAQ
What is the exact reset threshold voltage of the MAX6821ZUK+ and how does it vary with temperature?
The MAX6821ZUK+ has a nominal reset threshold of +2.32V, with tolerance of ±0.07V over the full operating temperature range of -40°C to +125°C. Its reset threshold temperature coefficient is 60ppm/°C, meaning drift is less than 15mV across the entire range. This specification is confirmed in the "Electrical Characteristics" table of Maxim's official datasheet Rev 3 (7/14), and applies exclusively to the Z-suffix variant of the MAX6821ZUK+.
Does the MAX6821ZUK+ require external components to operate?
No, the MAX6821ZUK+ operates autonomously with no external components required. It integrates an internal 50kΩ pullup on the MR pin, a precision voltage reference for threshold detection, and a monolithic watchdog timer. The only connections needed are VCC, GND, MR (optional), WDI (optional), and RESET - all defined in the pin configuration diagram on page 5 of the MAX6821ZUK+ datasheet.
How does the watchdog timer in the MAX6821ZUK+ respond to software faults?
The MAX6821ZUK+ watchdog timer triggers a reset if the WDI pin remains static (no rising or falling edge) for longer than 1.6s (1.12–2.4s over temperature). A detected edge clears the timer; during active reset assertion, the timer remains frozen. This behavior ensures recovery from infinite loops or stalled firmware - and is validated in Figure 3 ("Watchdog Timing Relationship") and the "Watchdog Input" section of the MAX6821ZUK+ datasheet.
Can the MAX6821ZUK+ assert reset when VCC drops below +1.0V?
No - the MAX6821ZUK+ guarantees correct RESET output state only down to VCC = +1.0V, not below. At VCC < +1.0V, reset behavior is undefined. However, the device continues asserting RESET as VCC falls from threshold to +1.0V, and holds it asserted throughout that range. This is explicitly stated in the "General Description" and "Absolute Maximum Ratings" sections of the MAX6821ZUK+ datasheet.
What is the function of Pin 3 (MR) on the MAX6821ZUK+ and how should it be used?
Pin 3 is the active-low Manual Reset (MR) input with an internal 50kΩ pullup to VCC. Driving MR low forces immediate RESET assertion, which persists for the full 140ms timeout after MR returns high. If unused, MR may be left floating (relying on internal pullup) or tied to VCC. This behavior is documented in the "Pin Description" table (page 5) and "Manual Reset Input" subsection of the MAX6821ZUK+ datasheet.
MAX6821ZUK+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- SC-74A, SOT-753
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Simple Reset/Power-On Reset
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 2.32V
- Output:
- Push-Pull, Totem Pole
- Reset:
- Active High
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-5
MAX6821ZUK+ FAQ
1.How can I place an order for MAX6821ZUK+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX6821ZUK+ 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 MAX6821ZUK+ reliable?
The price and inventory of MAX6821ZUK+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX6821ZUK+ is usually 5 days.
3.What payment methods are accepted for MAX6821ZUK+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX6821ZUK+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX6821ZUK+?
MAX6821ZUK+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX6821ZUK+ 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 MAX6821ZUK+?
For technical support, including MAX6821ZUK+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX6821ZUK+ requirements.
6.How does Aetrix verify that MAX6821ZUK+ is sourced from the original manufacturer or authorized distributors?
All MAX6821ZUK+ 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 MAX6821ZUK+ meets industry standards.
7.What is the process for return or replacement of MAX6821ZUK+?
All MAX6821ZUK+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX6821ZUK+, 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 MAX6821ZUK+ part is unused and in its original packaging.
Return procedure for MAX6821ZUK+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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