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Analog Devices Inc./Maxim Integrated MAX805SEPA+
- Part No.:
- MAX805SEPA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
MAX805SEPA+.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:619
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Product details
Overview
MAX805SEPA+ from Maxim Integrated is a 3.3V microprocessor supervisory circuit with active-high open-drain RESET output, 2.925V reset threshold (S-suffix), 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover capability. It monitors VCC supply integrity, asserts reset during brownout or watchdog timeout, and switches CMOS RAM to VBATT when VCC falls below 2.40V - used in embedded controllers and portable equipment requiring reliable power-up sequencing and data retention.
For engineers reviewing the MAX805SEPA+ datasheet, MAX805SEPA+ pinout, MAX805SEPA+ application, or MAX805SEPA+ equivalent, this page delivers verified technical context, exact pin functions, real-world use cases for battery-backed µP systems, and validated alternative parts with documented functional differences.
Technical Context
The MAX805SEPA+ integrates a precision reset comparator with ±4% threshold tolerance (2.925V nominal), a 1.6s watchdog timer that clears on WDI edge transitions, and a dual-path power switch: VCC-to-VOUT via 3Ω PMOS and VBATT-to-VOUT via 140Ω NMOS. Its PFI input accepts external voltage dividers for auxiliary supply monitoring, while PFO provides an independent low-active power-fail signal.
It operates across –40°C to +85°C (E-grade), supports VCC from 3.02V to 5.5V and VBATT up to 6.0V, guarantees RESET assertion down to VCC = 1.0V, and draws only 40µA typical VCC supply current - enabling long-term operation in battery-powered systems without compromising reset accuracy or timing stability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.925V (VCC falling), ±4% tolerance - ensures reset triggers before 3.3V supply drops below 2.85V system minimum. |
| Reset Timeout Period | 200ms (typical) - provides sufficient hold time for µP initialization after power stabilization. |
| Watchdog Timeout | 1.6s - detects µP lockup in real-time control loops without requiring software intervention. |
| VCC Supply Current | 40µA (typ, VCC < 3.6V) - enables multi-year operation on coin-cell batteries in standby mode. |
| Battery Leakage Current | 0.01–0.5µA - minimizes self-discharge of lithium backup cells during extended storage. |
| VBATT Switch Threshold | 2.40V (VCC rising), 65mV hysteresis - initiates switchover early enough to preserve CMOS RAM data above 2.0V. |
| PFO Input Threshold | 1.237V ±20mV - supports accurate undervoltage detection of auxiliary rails via resistor divider. |
Pinout & Package
MAX805SEPA+ is supplied in an 8-pin plastic DIP package (PDIP) with lead-free finish (+ suffix), 0.300" wide body, and through-hole mounting. Pin spacing conforms to JEDEC MS-001 standard.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - VOUT | CMOS RAM supply output | Switches between VCC (via 3Ω PMOS) and VBATT (via 140Ω NMOS); connects to RAM VDD to maintain data during brownout. |
| 2 - VCC | Main system supply input | Accepts 3.02V–5.5V; powers internal circuitry and enables VCC-to-VOUT path; reset asserted if VCC < 2.925V. |
| 3 - GND | Ground reference | Common return for all analog/digital functions; substrate tied to higher of VCC/VBATT per chip topology. |
| 4 - PFI | Power-fail input | Monitors auxiliary supply via external divider; trips PFO low when voltage falls below 1.237V. |
| 5 - PFO | Power-fail output | Open-drain, active-low signal indicating PFI undervoltage or VCC < 2.40V; can drive MR on MAX704/MAX806. |
| 6 - WDI | Watchdog input | Edge-sensitive (rising/falling); clears 1.6s timer on transition; no disable function - always active. |
| 7 - RESET | Active-high open-drain reset | Inverse of MAX690/704/802 RESET; requires external pull-up; asserts high for 200ms on fault or MR trigger. |
| 8 - VBATT | Backup battery input | Accepts 3.6V lithium cell; may exceed VCC; enables VOUT switchover when VCC drops below 2.40V. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed RESET assertion to VCC = 1V | Ensures fail-safe reset even during deep brownout - critical for retaining state in low-power µP sleep modes. |
| Battery-backup switchover with 2.40V threshold | Activates before VOUT reaches 2.0V RAM retention limit, extending data hold time without premature battery drain. |
| 200ms reset timeout with restart-on-brownout | Each VCC dip below 2.925V resets the timer - prevents spurious release during unstable power recovery. |
| 1.6s watchdog timer with edge-triggered clear | Eliminates need for periodic software "kick"; tolerates µP glitches while detecting true lockup. |
| 40µA VCC supply current (typ) | Reduces quiescent load on primary supply - extends battery life in always-on portable instrumentation. |
| ±4% reset threshold tolerance | Matches 3.3V ±10% system supply spec; avoids false resets due to nominal rail variation or temperature drift. |
Applications
| Battery-Powered Embedded Controller | Portable Medical Instrument |
|---|---|
Use Scenario: A handheld glucose meter uses a 3.3V µP and SRAM to store calibration data and recent readings between battery changes. IC Role / Device Role / Timing Role: MAX805SEPA+ monitors main 3.3V rail, asserts RESET during power-up/brownout, and switches SRAM to 3.6V lithium backup when VCC drops below 2.40V. Use Value: Guarantees RAM data retention down to VCC = 1.0V and prevents corrupted firmware execution during battery insertion/removal. |
Use Scenario: An ECG monitor runs on AA batteries and must retain patient waveform buffers during brief power interruptions caused by battery replacement. IC Role / Device Role / Timing Role: MAX805SEPA+ provides 200ms reset hold time and seamless VBATT switchover at 2.40V to sustain SRAM voltage above 2.0V. Use Value: Enables hot-swap battery operation without loss of clinical data - meeting IEC 60601-1 reliability requirements. |
| Industrial Data Logger | Smart Sensor Node |
Use Scenario: A remote environmental logger powered by solar-charged Li-ion operates unattended for months, storing sensor readings in nonvolatile SRAM. IC Role / Device Role / Timing Role: MAX805SEPA+ watches VCC, triggers watchdog reset if µP hangs during wireless transmission, and preserves SRAM via VBATT during nighttime low-light periods. Use Value: Eliminates field failures from µP lockup or brownout-induced memory corruption - reducing maintenance costs. |
Use Scenario: A LoRaWAN node sleeps most of the time but wakes periodically to sample temperature/humidity and transmit data. IC Role / Device Role / Timing Role: MAX805SEPA+ holds µP in reset until VCC stabilizes post-wakeup, monitors supply health, and guards against watchdog timeout during RF burst transmission. Use Value: Ensures deterministic boot sequence and prevents missed transmissions due to supply sag under RF load. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX805TEPA+ | Reset threshold = 3.075V (T-suffix), same package/timing/features | Suitable for 3.3V ±5% supplies where tighter brownout margin is required | Select when system VCC must remain ≥3.075V to avoid reset - e.g., high-precision ADC references. |
| MAX805REPA+ | Reset threshold = 2.625V (R-suffix), same package/timing/features | Designed for 3.0V ±10% systems; asserts reset later than S-version | Choose for legacy 3.0V designs or where extended brownout tolerance is needed before reset activation. |
Compared with MAX805SEPA+, the T-version offers earlier reset assertion for stricter 3.3V supply regulation, while the R-version delays reset to accommodate wider 3.0V supply tolerances - both share identical watchdog, switchover, and PFI/PFO functionality.
Availability
MAX805SEPA+ is available at Aetrix Electronics and suitable for battery-powered embedded controllers, portable medical instruments, industrial data loggers, smart sensor nodes, and critical µP power monitoring applications requiring stable component supply and long-term lifecycle support.
Supply support for MAX805SEPA+ 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, automotive, communications, and computing markets.
The MAX805SEPA+ belongs to Maxim's µP supervisory family targeting 3.0V/3.3V systems - engineered to replace discrete reset circuits with integrated reset, watchdog, and battery switchover in space-constrained, battery-sensitive applications.
FAQ
What is the reset threshold voltage of the MAX805SEPA+?
The MAX805SEPA+ has a nominal reset threshold voltage of 2.925V (S-suffix), specified with ±4% tolerance over temperature. This value applies to VCC falling conditions and ensures reset assertion before the 3.3V supply drops below 2.85V - matching typical 3.3V ±10% system specifications. The rising threshold is 2.935V, providing 10mV hysteresis to prevent oscillation near the trip point. MAX805SEPA+ guarantees valid reset operation down to VCC = 1.0V.
Does the MAX805SEPA+ support battery backup switching, and what is the switchover voltage?
Yes, the MAX805SEPA+ supports automatic battery backup switching via its VBATT pin. Switchover from VCC to VBATT occurs when VCC falls below 2.40V (VSW), with 65mV typical hysteresis. This ensures VOUT remains above 2.0V - the minimum required for reliable CMOS RAM data retention. When VCC recovers, VOUT reconnects to VCC only after VCC rises above the 2.925V reset threshold, preventing premature reversion during unstable recovery. MAX805SEPA+ allows VBATT to exceed VCC, supporting standard 3.6V lithium cells.
How does the watchdog timer in the MAX805SEPA+ operate, and can it be disabled?
The MAX805SEPA+ features a fixed 1.6s watchdog timer that cannot be disabled. It clears on any rising or falling edge at the WDI pin and triggers a reset if WDI remains static (high or low) for longer than 1.6s. Unlike older families, there is no hardware disable option - ensuring continuous supervision even if firmware fails to service the watchdog. The timer restarts immediately upon reset deassertion. MAX805SEPA+ guarantees this behavior across –40°C to +85°C and supports WDI logic levels of 0.3×VCC (low) and 0.7×VCC (high).
What is the function of the PFI and PFO pins on the MAX805SEPA+?
The PFI (Power-Fail Input) pin on the MAX805SEPA+ accepts an external voltage - typically from a resistor divider - and compares it to a 1.237V internal reference. When PFI falls below this threshold, the open-drain PFO (Power-Fail Output) pin pulls low. PFO can signal undervoltage on auxiliary rails or drive the MR input of compatible devices like MAX704/MAX806 to generate a system reset. If unused, PFI must be grounded and PFO left floating. MAX805SEPA+ specifies ±20mV PFI hysteresis to reject noise on monitored supplies.
Is the RESET output of the MAX805SEPA+ active-high or active-low, and what type of driver does it use?
The RESET output of the MAX805SEPA+ is active-high and open-drain - meaning it pulls low only when deasserted and requires an external pull-up resistor to VCC to generate a logic high when asserted. This configuration allows wired-OR connection with other reset sources and simplifies interfacing with µPs having bidirectional reset pins. The output sinks up to 1.2mA while asserted and maintains high impedance otherwise. MAX805SEPA+ guarantees RESET remains high for 200ms after fault clearance and stays asserted as long as VCC remains below 2.925V or MR is held low.
MAX805SEPA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Battery Backup Circuit
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 2.925V
- Output:
- Open Drain or Open Collector
- Reset:
- Active High
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
MAX805SEPA+ FAQ
1.How can I place an order for MAX805SEPA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX805SEPA+ 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 MAX805SEPA+ reliable?
The price and inventory of MAX805SEPA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX805SEPA+ is usually 5 days.
3.What payment methods are accepted for MAX805SEPA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX805SEPA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX805SEPA+?
MAX805SEPA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX805SEPA+ 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 MAX805SEPA+?
For technical support, including MAX805SEPA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX805SEPA+ requirements.
6.How does Aetrix verify that MAX805SEPA+ is sourced from the original manufacturer or authorized distributors?
All MAX805SEPA+ 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 MAX805SEPA+ meets industry standards.
7.What is the process for return or replacement of MAX805SEPA+?
All MAX805SEPA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX805SEPA+, 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 MAX805SEPA+ part is unused and in its original packaging.
Return procedure for MAX805SEPA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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