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Analog Devices Inc./Maxim Integrated MAX6821VUK+
- Part No.:
- MAX6821VUK+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- SC-74A, SOT-753
- Datasheet:
-
MAX6821VUK+.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:4,608
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Product details
Overview
MAX6821VUK+ from Maxim Integrated is a low-voltage microprocessor supervisory circuit in 5-pin SOT23 package, featuring push-pull active-low RESET output, 1.58V reset threshold (V suffix), 140ms minimum reset timeout, 1.6s watchdog timeout, and debounced manual reset input. It monitors VCC down to +1.0V and asserts reset during power-up, brownout, or software fault conditions in embedded controllers and portable equipment.
For engineers reviewing the MAX6821VUK+ datasheet, MAX6821VUK+ pinout, MAX6821VUK+ application, or MAX6821VUK+ equivalent, this device supports critical µP monitoring in battery-powered systems where guaranteed reset validity at low VCC, immunity to short VCC transients, and no external components are essential selection criteria.
Technical Context
The MAX6821VUK+ integrates voltage monitoring, watchdog timer, and manual reset into a single BiCMOS IC. Its reset generator triggers on VCC falling below 1.58V ±3%, holds RESET low for ≥140ms after VCC recovers, and includes internal 50kΩ MR pullup with 1µs minimum pulse width support.
The watchdog circuit monitors WDI transitions with 1.6s nominal timeout (0.8–2.6s over temperature), clears on any edge or reset assertion, and tolerates WDI leakage ≤10µA when unconnected. RESET output remains valid down to VCC = +1.0V, with VOL ≤0.3V at ISINK = 500µA and VOH ≥0.8×VCC at ISOURCE = 200µA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 1.58V ±3% - precisely matches 1.8V supply brownout detection with 20mV hysteresis |
| Reset Timeout Period | 140ms min - ensures µP completes power stabilization before release |
| Watchdog Timeout | 1.6s nominal (0.8–2.6s over -40°C to +125°C) - balances fault detection speed and noise immunity |
| Supply Current | 20µA max at +5.5V, +125°C - enables ultra-low-power operation in battery systems |
| Operating Voltage Range | +1.2V to +5.5V - supports operation during deep brownout while maintaining reset integrity |
| RESET Output Type | Push-pull active-low - drives µP reset pin directly without external pullup resistor |
| MR Input Logic | Active-low with 50kΩ internal pullup - eliminates need for external biasing; accepts CMOS-level signals |
Pinout & Package
Package: 5-pin SOT23-5 (U5-1 outline), footprint compatible with industry-standard 0.95mm pitch land pattern.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | RESET | Active-low push-pull reset output; sinks 500µA at 0.3V max, sources 200µA at 0.8×VCC min |
| 2 | GND | Ground reference for all internal circuits and reset timing accuracy |
| 3 | MR | Active-low manual reset input; internally pulled up to VCC (50kΩ); 1µs minimum pulse width |
| 4 | WDI | Watchdog input; edge-sensitive; clears 1.6s timer on rising/falling transition; disabled if floating |
| 5 | VCC | Supply and monitored voltage input; reset asserted when VCC falls below 1.58V; valid down to +1.0V |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed reset validity to VCC = +1.0V | Enables reliable reset assertion even during severe brownout or battery depletion in portable gear |
| No external components required | Reduces BOM count and PCB area; eliminates calibration resistors or RC timing networks |
| 140ms minimum reset timeout | Meets JEDEC JESD78 requirements for µP power-on reset duration across full temperature range |
| Immunity to short negative VCC transients | Withstands ≤20µs glitches down to 100mV below threshold without spurious reset assertion |
| Debounced manual reset input | Internal filtering eliminates need for external RC debounce circuitry on front-panel reset switches |
Applications
| Set-Top Boxes | Portable/Battery-Powered Equipment |
|---|---|
Use Scenario: Power sequencing and firmware recovery during AC dropout or cold boot. IC Role / Device Role / Timing Role: Critical µP monitoring supervisor asserting active-low reset to ARM-based SoC during brownout. Use Value: Prevents corrupted bootloaders by holding reset until 1.58V rail stabilizes for ≥140ms post-recovery. |
Use Scenario: Deep-sleep wake-up and low-battery reset in handheld medical instruments. IC Role / Device Role / Timing Role: Voltage monitor and watchdog enforcing safe restart when Li-ion drops below 2.8V. Use Value: Guarantees RESET remains valid down to VCC = +1.0V, enabling controlled shutdown before battery cutoff. |
| Embedded Controllers | Intelligent Instruments |
Use Scenario: Industrial PLC controller reboot after EMI-induced code hang. IC Role / Device Role / Timing Role: Watchdog timer monitoring WDI toggles from FPGA logic; triggers 1.6s timeout on stall. Use Value: Resets µP within 1.6s + 140ms, meeting IEC 61508 functional safety timing constraints. |
Use Scenario: Calibration data retention and firmware integrity check in benchtop DMMs. IC Role / Device Role / Timing Role: Manual reset input tied to front-panel switch; debounced internally for user-initiated recalibration. Use Value: Eliminates external debounce components, reducing failure points in high-reliability test equipment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar µP supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6822VUK+ | Open-drain RESET output instead of push-pull; identical threshold, timeout, and watchdog specs | Required when interfacing with bidirectional µP reset pins (e.g., Motorola 68HC11) needing external pullup | Select MAX6822VUK+ only if system design mandates open-drain drive; otherwise MAX6821VUK+ reduces component count |
| TPS3808G15DBVR | 1.5V threshold, 200ms reset timeout, no manual reset input; TI's BiCMOS process, different pinout | Lacks MR input and watchdog; suited for simpler reset-only applications without software fault detection | Choose TPS3808G15DBVR only when manual reset and watchdog functions are unnecessary; not drop-in compatible |
Compared with MAX6821VUK+, MAX6822VUK+ offers identical supervision functionality but requires an external pullup resistor due to open-drain output, whereas TPS3808G15DBVR omits both MR and watchdog-making MAX6821VUK+ the sole option supporting full-feature µP supervision in space-constrained SOT23 designs.
Availability
MAX6821VUK+ is available at Aetrix Electronics and suitable for set-top boxes, portable/battery-powered equipment, and embedded controllers requiring stable component supply with guaranteed long-term availability and RoHS-compliant packaging.
Supply support for MAX6821VUK+ 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 industrial, computing, and consumer applications.
The MAX6821–MAX6825 family delivers integrated µP supervision in ultra-small SOT23 packages, targeting space- and power-constrained embedded systems needing reliable reset, watchdog, and manual reset functions.
FAQ
What is the exact reset threshold voltage of the MAX6821VUK+?
The MAX6821VUK+ has a factory-trimmed reset threshold of 1.58V ±3% over the full operating temperature range (-40°C to +125°C). This value is confirmed in the Electrical Characteristics table under "VTH" for suffix "V", with typical hysteresis of 2×VTH (≈3.16mV) ensuring noise immunity during voltage recovery.
Does the MAX6821VUK+ require external components for basic operation?
No, the MAX6821VUK+ operates autonomously with no external components required. Its internal 50kΩ MR pullup resistor, precise voltage reference, and self-timed reset/watchdog circuits eliminate the need for external resistors, capacitors, or timing elements-reducing BOM cost and PCB footprint.
How does the watchdog timer in the MAX6821VUK+ respond to software faults?
The MAX6821VUK+ watchdog timer triggers a reset if the WDI pin remains static (high or low) for longer than 1.6s (nominal). A rising or falling edge on WDI clears the timer; thus, firmware must toggle WDI at least once per timeout period to prevent unintended reset-enabling detection of infinite loops or stalled execution.
Can the MAX6821VUK+ operate reliably during battery voltage sag?
Yes, the MAX6821VUK+ guarantees correct RESET output state down to VCC = +1.0V, well below its 1.58V threshold. This ensures deterministic reset assertion even during deep battery discharge in portable equipment, preventing erratic µP behavior before complete power loss.
What is the function of Pin 3 (MR) on the MAX6821VUK+?
Pin 3 (MR) is the active-low manual reset input on the MAX6821VUK+. Pulling MR low forces an immediate reset assertion for ≥140ms after MR returns high. With an internal 50kΩ pullup, MR can be left unconnected if unused-or driven by a momentary switch to GND for field-serviceable reset capability.
MAX6821VUK+ 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:
- 1.58V
- 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
MAX6821VUK+ FAQ
1.How can I place an order for MAX6821VUK+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX6821VUK+ 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 MAX6821VUK+ reliable?
The price and inventory of MAX6821VUK+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX6821VUK+ is usually 5 days.
3.What payment methods are accepted for MAX6821VUK+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX6821VUK+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX6821VUK+?
MAX6821VUK+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX6821VUK+ 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 MAX6821VUK+?
For technical support, including MAX6821VUK+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX6821VUK+ requirements.
6.How does Aetrix verify that MAX6821VUK+ is sourced from the original manufacturer or authorized distributors?
All MAX6821VUK+ 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 MAX6821VUK+ meets industry standards.
7.What is the process for return or replacement of MAX6821VUK+?
All MAX6821VUK+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX6821VUK+, 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 MAX6821VUK+ part is unused and in its original packaging.
Return procedure for MAX6821VUK+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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