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Analog Devices Inc./Maxim Integrated MAX805SCSA+T
- Part No.:
- MAX805SCSA+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX805SCSA+T.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,113
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Product details
Overview
MAX805SCSA+T from Maxim Integrated is a 3.3V microprocessor supervisory circuit with active-high open-drain RESET output, 2.925V reset threshold, 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 sequencing.
For engineers reviewing the MAX805SCSA+T datasheet, MAX805SCSA+T pinout, MAX805SCSA+T application, or MAX805SCSA+T equivalent, key selection criteria include reset threshold accuracy (±2% for MAX805S), battery-switch hysteresis (25mV typical), VCC-to-VOUT on-resistance (3Ω), guaranteed RESET assertion down to VCC = 1V, and compatibility with lithium backup cells exceeding VCC.
Technical Context
The MAX805SCSA+T integrates a precision reset comparator with 2.925V nominal threshold (VCC rising: 2.85V–3.02V), a 1.6s watchdog timer cleared by WDI edges, 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 at 1.237V threshold with 10mV hysteresis.
Battery switchover occurs at VSW = 2.40V (VBATT > VCC) on power-down and defers reconnection to VCC until VCC rises above the reset threshold-ensuring stable supply before RAM reconnection. The device operates across –40°C to +85°C, draws 40µA VCC supply current (VCC < 3.6V), and supports manual reset with 70µA internal pull-up.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.925V (VCC falling), ±2% tolerance - ensures reset assertion before 3.3V supply drops below system stability margin. |
| Reset Timeout Period | 200ms (typical) - guarantees µP remains held in reset long enough for power stabilization after VCC recovery. |
| Watchdog Timeout | 1.6s - detects µP lockup if WDI fails to toggle; timer clears on any edge, preventing false triggers. |
| VCC Supply Current | 40µA (VCC < 3.6V, TA = +25°C) - enables ultra-low-power operation in battery-backed systems. |
| Battery Leakage Current | 0.01–0.5µA - minimizes self-discharge of lithium backup cells during long-term storage. |
| VCC-to-VOUT On-Resistance | 3Ω (typical) - limits voltage drop under 50mA load, preserving RAM retention voltage. |
| VBATT-to-VOUT On-Resistance | 140Ω (typical) - balances low-loss backup delivery with controlled inrush during switchover. |
Pinout & Package
MAX805SCSA+T is housed in an 8-pin SOIC package (SO, 150mil width), RoHS-compliant (indicated by '+' suffix), with standard JEDEC MS-012AC outline and thermal pad not connected.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1: VOUT | CMOS RAM supply output | Switches between VCC (via 3Ω PMOS) and VBATT (via 140Ω NMOS); must be decoupled with 0.1µF capacitor. |
| 2: VCC | Main system supply input | Accepts 3.02V–5.5V; powers internal circuitry and drives VOUT when above reset threshold. |
| 3: GND | Ground reference | Common return for all analog/digital functions; substrate tied to higher of VCC/VBATT. |
| 4: PFI | Power-fail input | Monitors auxiliary supply via external divider; trips PFO low when voltage falls below 1.237V. |
| 5: PFO | Power-fail open-drain output | Active-low signal indicating PFI undervoltage or VCC < VSW; can drive MR on MAX704/MAX806. |
| 6: WDI | Watchdog input | Edge-sensitive (rising/falling); resets watchdog timer; cannot be disabled. |
| 7: RESET | Active-high open-drain reset output | Inverse of MAX690/704/802 RESET; requires external pull-up to VCC for logic-high level. |
| 8: VBATT | Backup battery input | Supports voltages up to 6.0V; may exceed VCC; connects to VOUT during brownout. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed RESET assertion to VCC = 1V | Ensures fail-safe reset even during deep brownout, critical for data retention in low-VCC conditions. |
| Battery-backup switchover at 2.40V | Triggers before CMOS RAM minimum retention voltage (2.0V), maximizing backup duration without premature switch. |
| ±2% reset threshold tolerance (MAX805S) | Tighter than MAX690S (±4%), enabling robust operation in 3.3V ±10% systems without margin overdesign. |
| 1µA typical VBATT supply current | Extends shelf life of lithium coin cells beyond 10 years in standby, reducing maintenance in remote deployments. |
| 25mV typical hysteresis on VCC-to-VBATT comparator | Prevents oscillation during slow VCC ramp-down, eliminating chatter on VOUT during switchover. |
Applications
| Battery-Powered Embedded Controllers | Intelligent Portable Instruments |
|---|---|
Use Scenario: Industrial handheld meter with lithium backup powering SRAM and real-time clock during main supply interruption. IC Role / Device Role / Timing Role: Supervisory IC providing brownout detection, 200ms reset hold, and seamless VBATT switchover at 2.40V. Use Value: Prevents data corruption during field battery swaps and extends operational uptime via low 1µA VBATT leakage. |
Use Scenario: Portable medical diagnostic device requiring guaranteed reset on power-up and watchdog supervision of firmware execution. IC Role / Device Role / Timing Role: Active-high RESET output interfaces directly to µP reset pin; 1.6s watchdog enforces firmware liveness. Use Value: Eliminates need for discrete RC reset circuits and external watchdog ICs, reducing BOM count and PCB area. |
| Critical µP Power Monitoring | Portable Computing Peripherals |
Use Scenario: USB-powered peripheral with volatile configuration memory that must retain state across host suspend/resume cycles. IC Role / Device Role / Timing Role: Monitors 3.3V rail; asserts RESET if VCC dips below 2.925V; uses PFI to detect USB VBUS dropout. Use Value: 10mV PFI hysteresis rejects noise on divided VBUS line, preventing spurious resets during transient load changes. |
Use Scenario: Bluetooth audio headset with flash memory and sensor subsystem requiring clean power sequencing on battery insertion. IC Role / Device Role / Timing Role: Provides 200ms power-on reset delay and manual reset via pushbutton on MR pin. Use Value: Internal 70µA MR pull-up eliminates external resistor, simplifying layout and reducing component count. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX804SCSA+T | Active-low RESET output (push-pull), same 2.925V threshold and 200ms timeout | Requires no external pull-up; better suited for µPs with active-low reset inputs | Select MAX804SCSA+T when interfacing to legacy µPs expecting active-low reset assertion without pull-up. |
| MAX706SCSA+T | No watchdog timer, no battery switchover; 2.93V reset threshold, 140ms timeout | Lower cost, simpler function set; intended for non-battery-backed applications only | Choose MAX706SCSA+T only if battery backup and watchdog supervision are unnecessary and shorter reset hold is acceptable. |
Compared with MAX804SCSA+T, MAX805SCSA+T provides active-high reset compatible with newer µPs but requires external pull-up; versus MAX706SCSA+T, it adds critical watchdog and battery switchover-justifying its use in safety-critical portable systems where firmware reliability and data retention are mandatory.
Availability
MAX805SCSA+T is available at Aetrix Electronics and suitable for battery-powered computers and controllers, intelligent instruments, and critical µP power monitoring requiring stable component supply across industrial temperature ranges.
Supply support for MAX805SCSA+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, designs high-performance analog and mixed-signal ICs for power, sensing, and connectivity applications.
The MAX805SCSA+T belongs to Maxim's 3.0V/3.3V microprocessor supervisory family, engineered specifically for reliable power monitoring, reset generation, and battery-backed RAM preservation in space-constrained portable and embedded systems.
FAQ
What is the exact reset threshold voltage of the MAX805SCSA+T?
The MAX805SCSA+T has a nominal reset threshold of 2.925V, specified as 2.85V (min) to 3.00V (max) for VCC falling and 2.85V to 3.02V for VCC rising. This ±2% tolerance is tighter than the MAX690S series and ensures precise brownout detection in 3.3V ±10% systems. The threshold is factory-trimmed and tested across temperature.
Does the MAX805SCSA+T support battery voltages higher than VCC?
Yes, the MAX805SCSA+T explicitly supports VBATT exceeding VCC-up to 6.0V-as confirmed in Absolute Maximum Ratings and Backup-Battery Switchover section. When VCC falls below 2.40V and VBATT > VCC, VOUT automatically switches to VBATT, enabling use with standard 3.6V lithium cells without level-shifting circuitry.
How does the watchdog timer in the MAX805SCSA+T operate?
The MAX805SCSA+T watchdog timer has a fixed 1.6s timeout (1.12s–2.24s over temperature). It clears on any WDI edge (rising or falling) and triggers reset if WDI remains static. Unlike older families, the watchdog cannot be disabled. Reset deassertion restarts the timer, ensuring continuous µP supervision during normal operation.
Can the MAX805SCSA+T be used without a backup battery?
Yes, but with modification: connect both VBATT and VOUT pins directly to VCC. The MAX805SCSA+T is designed for battery-backed applications; omitting the battery while leaving VBATT floating or unconnected risks undefined behavior. For non-battery applications, Maxim recommends alternatives like MAX706SCSA+T.
What is the purpose of the PFI and PFO pins on the MAX805SCSA+T?
PFI is a dedicated input for monitoring auxiliary power supplies via external resistor dividers, comparing against a 1.237V internal reference. PFO is its open-drain output, going low when PFI falls below threshold or VCC drops below 2.40V. PFO can drive MR on MAX704/MAX806 devices to generate cascaded resets, extending fault coverage beyond primary VCC monitoring.
MAX805SCSA+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX805SCSA+T FAQ
1.How can I place an order for MAX805SCSA+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX805SCSA+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 MAX805SCSA+T reliable?
The price and inventory of MAX805SCSA+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX805SCSA+T is usually 5 days.
3.What payment methods are accepted for MAX805SCSA+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX805SCSA+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX805SCSA+T?
MAX805SCSA+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX805SCSA+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 MAX805SCSA+T?
For technical support, including MAX805SCSA+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX805SCSA+T requirements.
6.How does Aetrix verify that MAX805SCSA+T is sourced from the original manufacturer or authorized distributors?
All MAX805SCSA+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 MAX805SCSA+T meets industry standards.
7.What is the process for return or replacement of MAX805SCSA+T?
All MAX805SCSA+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX805SCSA+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 MAX805SCSA+T part is unused and in its original packaging.
Return procedure for MAX805SCSA+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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