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Analog Devices Inc./Maxim Integrated MAX805RESA+
- Part No.:
- MAX805RESA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX805RESA+.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:228
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Product details
Overview
MAX805RESA+ from Maxim Integrated is a 3.0V/3.3V microprocessor supervisory circuit with active-high open-drain RESET output, 2.625V reset threshold (R-suffix), 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover. It monitors VCC supply integrity, asserts reset during brownout or watchdog timeout, and switches CMOS RAM to VBATT when VCC drops below 2.40V - used in embedded controllers and portable equipment requiring reliable power-up sequencing and data retention.
For engineers reviewing the MAX805RESA+ datasheet, MAX805RESA+ pinout, MAX805RESA+ application, or MAX805RESA+ equivalent, this page delivers verified technical context, exact pin functions, real-world timing behavior, battery-switching design meaning, and validated alternative options for 3V/3.3V µP supervision with ±2% reset threshold tolerance.
Technical Context
The MAX805RESA+ integrates a precision reset comparator with 2.625V nominal threshold (±2% over temperature), 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 monitors external supplies at 1.237V with 10mV hysteresis, while RESET remains high-impedance until asserted.
It operates across –40°C to +85°C (E-grade), supports VCC from 2.72V to 5.5V and VBATT up to 6.0V, draws only 40µA typical VCC supply current, and guarantees RESET assertion down to VCC = 1.0V - enabling robust brownout detection even under severe undervoltage conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.625V (±2%), precisely calibrated for 3.0V ±10% systems - ensures reset triggers before VCC falls below 2.59V, preventing µP operation in unstable voltage regions. |
| Reset Timeout Period | 200ms (140–280ms over temp), fixed internal timer - guarantees sufficient hold time for µP initialization after power-up or brownout recovery. |
| Watchdog Timeout | 1.6s (1.12–2.24s), non-disableable timer cleared by WDI edges - detects µP lockup without software intervention, critical for unattended systems. |
| VCC Supply Current | 40µA typical (VCC < 3.6V), ultra-low quiescent draw - extends battery life in always-on portable applications without sacrificing supervision accuracy. |
| Battery Leakage Current | 0.01–0.5µA (C/E grade), sub-1µA VBATT standby drain - preserves lithium cell capacity over years of backup operation. |
| Power-Fail Threshold | 1.237V ±10mV at PFI input - enables accurate monitoring of auxiliary rails (e.g., 5V or –5V) via resistor divider, independent of main reset path. |
| VBATT Switch Threshold | VSW = 2.40V (2.30–2.50V), hysteresis-enabled switchover - initiates battery backup before VOUT drops below 2.0V, ensuring CMOS RAM data retention. |
Pinout & Package
MAX805RESA+ is housed in an 8-pin SOIC package (SO, 150mil width), RoHS-compliant with "+" suffix, suitable for surface-mount assembly and industrial temperature operation (–40°C to +85°C).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - VOUT | Supply output for CMOS RAM | Switches between VCC (via 3Ω PMOS) and VBATT (via 140Ω NMOS); connects to RAM VDD - must be decoupled with 0.1µF capacitor. |
| 2 - VCC | Main system supply input | Primary power source (2.72–5.5V); powers internal circuitry and enables VCC-to-VOUT path; monitored for reset and watchdog functions. |
| 3 - GND | Ground reference | Common return for all analog and digital blocks; substrate tied to higher of VCC/VBATT - must be low-impedance connection. |
| 4 - PFI | Power-fail input | Monitors external rail via resistor divider; trips PFO low when voltage falls below 1.237V - used for secondary supply monitoring or low-battery warning. |
| 5 - PFO | Power-fail output | Open-drain active-low signal; asserts when PFI < 1.237V or VCC < VSW - can drive MR on MAX704/MAX806 to trigger cascaded reset. |
| 6 - WDI | Watchdog input | Edge-sensitive (rising/falling) input; resets watchdog timer on transition; tied high/low causes 1.6s timeout - no pull-up/pull-down required. |
| 7 - RESET | Active-high open-drain reset output | Inverse of MAX690-style RESET; requires external pull-up to VCC; drives µP reset pin directly - compatible with bidirectional I/O when buffered. |
| 8 - VBATT | Backup battery input | Accepts 0–6.0V; may exceed VCC (e.g., 3.6V Li-cell); enables seamless switchover to preserve RAM during main supply failure. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed RESET assertion to VCC = 1V | Ensures fail-safe reset activation even during deep brownout, preventing µP execution in undefined states. |
| Battery-backup switchover with 2.40V threshold | Activates backup power before VOUT drops below 2.0V, preserving CMOS RAM contents without external circuitry. |
| 200ms reset timeout with automatic restart on VCC dip | Provides consistent reset pulse width regardless of how many times VCC crosses threshold - eliminates race conditions. |
| 1.237V ±10mV PFI comparator with independent enable | Allows monitoring of secondary supplies (e.g., 5V, –5V) without affecting primary reset function - enhances system-level fault coverage. |
| 40µA VCC supply current (typ) | Minimizes load on primary supply in battery-powered systems, extending operational lifetime without compromising supervision fidelity. |
Applications
| Battery-Powered Embedded Controller | Portable Medical Instrument |
|---|---|
Use Scenario: A handheld glucose meter uses a 3.0V coin-cell battery and ARM Cortex-M0 µP with static RAM for calibration data storage. IC Role / Device Role / Timing Role: MAX805RESA+ monitors VCC, asserts RESET on brownout, and switches RAM to VBATT within 2.40V switchover window to retain settings. Use Value: Guarantees data integrity during battery depletion and enables cold-start reliability - no data loss across 10,000+ power cycles. |
Use Scenario: A portable ECG device operates from rechargeable Li-ion (3.6V) and requires continuous memory retention during charging interruptions. IC Role / Device Role / Timing Role: MAX805RESA+ provides 200ms reset hold time on power-up and activates VBATT switchover at 2.40V to sustain RAM voltage above 2.0V. Use Value: Eliminates need for external backup diodes or regulators - reduces BOM count by 3 components while meeting IEC 60601-1 reliability requirements. |
| Industrial PLC Remote I/O Module | Smart Sensor Node with Watchdog |
Use Scenario: A DIN-rail mounted I/O module powered by 3.3V DC-DC converter experiences intermittent field wiring faults causing VCC dips. IC Role / Device Role / Timing Role: MAX805RESA+ detects sub-2.625V excursions, holds RESET low for 200ms, and restarts µP cleanly after each brownout event. Use Value: Prevents firmware corruption during transient line faults - achieves >99.99% uptime in 24/7 factory automation environments. |
Use Scenario: A LoRaWAN environmental sensor node runs on AA batteries and must recover autonomously from µP lockups caused by RF interference. IC Role / Device Role / Timing Role: MAX805RESA+ watches WDI pin; if µP fails to toggle it within 1.6s, it forces RESET to reboot the system without host intervention. Use Value: Enables fully autonomous field operation for 5+ years - eliminates manual resets and remote firmware updates for stuck nodes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX805TESA+ | 3.075V reset threshold (±2%), identical pinout and features | Designed for 3.3V ±5% systems; asserts reset earlier than R-suffix during gradual VCC decay | Select when main supply is tightly regulated 3.3V and brownout margin must align with ±5% spec. |
| MAX804RESA+ | Same 2.625V threshold, but active-low RESET (push-pull), no WDI pin | Lacks watchdog functionality; RESET output drives low actively instead of open-drain high | Choose when watchdog is unnecessary and µP reset pin requires direct active-low drive without pull-up. |
Compared with MAX805RESA+, MAX805TESA+ offers tighter reset timing for stable 3.3V rails, while MAX804RESA+ trades watchdog capability for simpler reset control - both share identical SOIC packaging and battery switchover, making them drop-in alternatives only where functional alignment matches system requirements.
Availability
MAX805RESA+ is available at Aetrix Electronics and suitable for battery-powered computers and controllers, embedded controllers, and intelligent instruments requiring stable component supply with guaranteed long-term availability and full traceability.
Supply support for MAX805RESA+ 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 and mixed-signal ICs for power management, sensing, and interface applications in industrial, medical, and communications systems.
The MAX805RESA+ belongs to Maxim's µP supervisory family engineered specifically for 3.0V/3.3V systems needing accurate reset, watchdog, and battery-backup switching - targeting applications where data integrity and autonomous recovery are mission-critical.
FAQ
What is the exact reset threshold voltage for MAX805RESA+ and how is it specified?
The MAX805RESA+ has a nominal reset threshold of 2.625V, with ±2% tolerance over temperature (–40°C to +85°C). This value is specified for VCC rising and falling conditions per the datasheet's Electrical Characteristics table, and applies strictly to the R-suffix variant. The threshold is laser-trimmed during production and guaranteed not to assert reset above 2.70V or fail to assert below 2.55V.
Does MAX805RESA+ support watchdog functionality, and what is its timeout behavior?
Yes, MAX805RESA+ includes a non-disableable watchdog timer with a nominal timeout of 1.6 seconds (1.12–2.24s over temperature). The timer clears on any rising or falling edge at the WDI pin and triggers RESET if WDI remains static beyond timeout. It remains inactive while RESET is asserted, and resumes counting immediately upon RESET deassertion.
How does the battery-backup switchover work on MAX805RESA+, and what is the VSW voltage?
MAX805RESA+ switches VOUT from VCC to VBATT when VCC falls below the battery switchover threshold VSW = 2.40V (2.30–2.50V), provided VBATT exceeds VCC. Switchover occurs through a 140Ω internal NMOS switch. When VCC recovers above the 2.625V reset threshold, VOUT reconnects to VCC via a 3Ω PMOS switch - ensuring clean transition without glitches.
Can MAX805RESA+ operate without a backup battery, and what connections are required?
Yes, MAX805RESA+ can operate without a backup battery: connect both VBATT and VOUT pins directly to VCC. This disables battery switchover and configures VOUT as a direct VCC output. Do not leave VBATT floating - tying it to VCC ensures proper internal biasing and prevents undefined behavior in the switchover comparator.
What is the function of the PFI and PFO pins on MAX805RESA+, and how are they used?
PFI is a dedicated input referenced to 1.237V ±10mV; when voltage at PFI falls below this threshold, PFO (an open-drain active-low output) pulls low. This allows monitoring of auxiliary supplies (e.g., 5V rail via resistor divider) or low-battery detection. PFO can be wired to MR on MAX704/MAX806 devices to generate a cascaded reset, or used as an interrupt to the µP.
MAX805RESA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Battery Backup Circuit
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 2.625V
- Output:
- Open Drain or Open Collector
- Reset:
- Active High
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX805RESA+ FAQ
1.How can I place an order for MAX805RESA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX805RESA+ 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 MAX805RESA+ reliable?
The price and inventory of MAX805RESA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX805RESA+ is usually 5 days.
3.What payment methods are accepted for MAX805RESA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX805RESA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX805RESA+?
MAX805RESA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX805RESA+ 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 MAX805RESA+?
For technical support, including MAX805RESA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX805RESA+ requirements.
6.How does Aetrix verify that MAX805RESA+ is sourced from the original manufacturer or authorized distributors?
All MAX805RESA+ 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 MAX805RESA+ meets industry standards.
7.What is the process for return or replacement of MAX805RESA+?
All MAX805RESA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX805RESA+, 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 MAX805RESA+ part is unused and in its original packaging.
Return procedure for MAX805RESA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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