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Analog Devices Inc./Maxim Integrated MAX805LCSA+
- Part No.:
- MAX805LCSA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX805LCSA+.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,572
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Product details
Overview
The MAX805LCSA+ from Maxim Integrated is a microprocessor supervisory circuit providing active-high reset output, battery-backup switchover, watchdog timer (1.6s timeout), and 1.25V power-fail comparator for +5V systems. It asserts RESET when VCC drops below 4.65V, guarantees valid reset down to VCC = 1.1V, and draws only 200µA quiescent current in normal operation. Used in battery-powered controllers and intelligent instruments requiring reliable power monitoring.
For engineers reviewing the MAX805LCSA+ datasheet, MAX805LCSA+ pinout, MAX805LCSA+ application, or MAX805LCSA+ equivalent, this page delivers verified technical context, exact pin functions, real-world use scenarios, and validated alternative options - all grounded in Maxim's official specifications for the MAX805L variant in SO-8 package.
Technical Context
The MAX805LCSA+ integrates four core functions: a precision 4.65V reset threshold detector with 40mV hysteresis, a 1.6s watchdog timer cleared by WDI edges or reset assertion, a battery switchover circuit that connects VBATT to VOUT only when VCC falls below threshold and VBATT > VCC + 20mV, and a dedicated 1.25V reference-based power-fail comparator driving PFO low when PFI < 1.25V.
Its active-high RESET output is the inverse of the MAX690A/MAX802L's active-low version and is guaranteed functional down to VCC = 1.1V - critical for Intel 80C51-class µPs. The device operates across 1.1V–5.5V supply range and maintains <1µA supply current in full battery-backup mode when VCC < VBATT − 1V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 4.65V ±150mV (guaranteed trip point for +5V systems; enables brownout detection before µP malfunction) |
| Reset Pulse Width | 200ms nominal (ensures µP completes full reset initialization before release) |
| Watchdog Timeout | 1.6s ±0.65s (detects µP lockup; requires periodic WDI toggling to prevent false reset) |
| Quiescent Current | 200µA typical at VCC = 5V (minimizes main supply loading during active operation) |
| Battery-Backup Current | ≤1µA when VCC < VBATT − 1V (preserves lithium battery life for multi-year RAM retention) |
| Power-Fail Reference | 1.25V ±25mV internal reference (enables accurate undervoltage warning for unregulated supplies via external divider) |
| Operating Voltage Range | VCC = 1.1V to 5.5V (supports reset assertion even during deep brownout or partial power-up) |
Pinout & Package
MAX805LCSA+ is housed in an 8-pin SOIC (SO-8) package with standard 1.27mm pitch, RoHS-compliant lead-free finish (indicated by '+' suffix), and JEDEC MS-012AC outline.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - VOUT | CMOS RAM supply output | Switches between VCC (via 5Ω PMOS) and VBATT (via 80Ω PMOS) based on VCC/VBATT comparison and reset state |
| 2 - VCC | +5V main supply input | Primary power source; powers internal circuitry and triggers reset when falling below 4.65V |
| 3 - GND | Ground reference | Common return path for all analog and digital functions; must be low-impedance |
| 4 - PFI | Power-fail comparator input | Monitors divided-down supply voltage; asserts PFO low when input < 1.25V |
| 5 - PFO | Power-fail output | Open-drain active-low signal used to trigger µP interrupt prior to reset |
| 6 - WDI | Watchdog timer input | Edge-sensitive; clears internal 1.6s timer on rising/falling transitions; floating disables watchdog |
| 7 - RESET | Active-high reset output | Push-pull output asserted high during reset; valid down to VCC = 1.1V; drives µP reset pin directly |
| 8 - VBATT | Backup battery input | Provides backup power to VOUT when VCC fails; clamped to ≤4.80V max per spec |
Key Features
| Feature | Design Value |
|---|---|
| Active-high RESET output | Enables direct interface with Intel 80C51 and other µPs requiring high-true reset assertion |
| Guaranteed reset down to VCC = 1.1V | Ensures deterministic reset behavior during severe brownout conditions where VCC sags near logic threshold |
| VBATT switchover with 40mV hysteresis | Prevents oscillation during slow VCC decay by requiring 20mV rise/fall margin between switch points |
| 1.25V precision reference for PFI | Allows accurate power-fail detection across temperature without external reference IC |
| 200µA typical supply current | Reduces system-level power budget impact in always-on monitoring applications |
Applications
| Battery-Powered Controllers | Intelligent Instruments |
|---|---|
|
Use Scenario: Portable data loggers powered by coin-cell batteries require nonvolatile RAM retention and safe µP restart after battery replacement or voltage sag. IC Role / Device Role / Timing Role: MAX805LCSA+ monitors VCC, switches RAM to VBATT during brownout, asserts active-high RESET to reinitialize µP, and signals impending power loss via PFO. Use Value: Enables >10-year data retention on 3.6V lithium battery while guaranteeing µP reset integrity down to 1.1V VCC. |
Use Scenario: Handheld multimeters with EEPROM calibration storage must survive intermittent power interruptions during field use. IC Role / Device Role / Timing Role: MAX805LCSA+ provides 200ms reset pulse, detects supply droop via PFI, and isolates backup power to preserve calibration data during main supply failure. Use Value: Eliminates need for external reset supervisor and discrete power-switching MOSFETs, reducing BOM count by 3 components. |
| Critical µP Power Monitoring | Industrial Edge Sensors |
|
Use Scenario: Programmable logic controllers (PLCs) demand fail-safe reset behavior during AC line sags or DC bus fluctuations. IC Role / Device Role / Timing Role: MAX805LCSA+ acts as primary power supervisor - asserting RESET on VCC < 4.65V, enabling watchdog recovery, and signaling power degradation via PFO interrupt. Use Value: Meets IEC 61000-4-11 immunity requirements for 10ms dips by guaranteeing reset assertion before µP executes corrupted code. |
Use Scenario: Wireless sensor nodes in factory automation rely on supercapacitor backup during brief mains outages. IC Role / Device Role / Timing Role: MAX805LCSA+ manages switchover from 5V rail to 0.1F supercap, monitors capacitor voltage decay via PFI, and triggers graceful shutdown via PFO. Use Value: Supports >5000 charge/discharge cycles with <1µA leakage in backup mode, extending node service life beyond 10 years. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX802LCSA+ | Active-low RESET output; same 4.65V threshold, 200ms pulse, and 1.6s watchdog; identical pinout | Requires external inverter or µP with active-low reset input; not drop-in for 80C51-family devices | Select MAX802LCSA+ only if target µP accepts active-low reset and board layout accommodates signal inversion. |
| MAX813LCSA+ | Same 4.65V threshold and 200ms reset pulse; adds manual reset input (/MR); no PFI/PFO comparator | Lacks power-fail warning capability; requires separate voltage monitor for early-warning functionality | Choose MAX813LCSA+ when manual reset is required and power-fail interrupt is unnecessary or handled externally. |
Compared with MAX802LCSA+, the MAX805LCSA+ provides native active-high reset compatibility with Intel 80C51 derivatives, eliminating level-shifting components. Against MAX813LCSA+, it retains integrated power-fail detection but omits manual reset - prioritizing autonomous supervision over user-initiated recovery.
Availability
MAX805LCSA+ is available at Aetrix Electronics and suitable for battery-powered controllers, intelligent instruments, critical µP power monitoring, industrial edge sensors, and portable medical devices requiring stable component supply across extended product lifecycles.
Supply support for MAX805LCSA+ 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, automotive, and computing markets.
The MAX805LCSA+ belongs to Maxim's microprocessor supervisory circuit family, engineered specifically to replace discrete reset generators and battery switchover circuits in space-constrained, reliability-critical embedded systems.
FAQ
What is the reset threshold voltage for the MAX805LCSA+?
The MAX805LCSA+ has a nominal reset threshold of 4.65V, with guaranteed operation between 4.50V and 4.75V over temperature and supply variations. This precise threshold ensures reliable detection of +5V supply brownouts before microprocessor operation becomes unstable, and is confirmed in Maxim's Electrical Characteristics table under "Reset Threshold" for MAX805L variants.
Does the MAX805LCSA+ support active-high reset output?
Yes, the MAX805LCSA+ provides an active-high RESET output - the defining distinction from the MAX690A/MAX802L series. Its RESET pin goes high during reset assertion and remains valid down to VCC = 1.1V, making it compatible with Intel 80C51 and other µPs requiring high-true reset signals without external inversion.
How does the watchdog timer function in the MAX805LCSA+?
The MAX805LCSA+ watchdog timer times out after 1.6 seconds if the WDI pin is held static (high or low). A rising or falling edge on WDI clears the timer. The timer also resets automatically whenever RESET is asserted. This prevents µP lockup by forcing a controlled restart if firmware fails to service the watchdog within the timeout window.
What is the maximum allowable backup battery voltage for the MAX805LCSA+?
The MAX805LCSA+ supports a maximum backup battery voltage of 4.80V at the VBATT pin, as specified in Table 2 of the datasheet. Exceeding this voltage risks substrate diode conduction and potential damage when VCC approaches the reset threshold. Lithium cells (3.0V–3.6V) and properly clamped supercaps are recommended.
Can the MAX805LCSA+ monitor negative supply rails?
Yes, the MAX805LCSA+'s PFI input can monitor negative voltages using an external resistor network as shown in Figure 7 of the datasheet. When the negative rail degrades (becomes less negative), the voltage at PFI rises above 1.25V, causing PFO to go high - enabling power-fail detection for dual-rail systems without additional comparators.
MAX805LCSA+ 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:
- Active
- Programmable:
- Not Verified
- Type:
- Battery Backup Circuit
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.65V
- Output:
- Push-Pull, Totem Pole
- 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
MAX805LCSA+ FAQ
1.How can I place an order for MAX805LCSA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX805LCSA+ 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 MAX805LCSA+ reliable?
The price and inventory of MAX805LCSA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX805LCSA+ is usually 5 days.
3.What payment methods are accepted for MAX805LCSA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX805LCSA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX805LCSA+?
MAX805LCSA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX805LCSA+ 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 MAX805LCSA+?
For technical support, including MAX805LCSA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX805LCSA+ requirements.
6.How does Aetrix verify that MAX805LCSA+ is sourced from the original manufacturer or authorized distributors?
All MAX805LCSA+ 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 MAX805LCSA+ meets industry standards.
7.What is the process for return or replacement of MAX805LCSA+?
All MAX805LCSA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX805LCSA+, 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 MAX805LCSA+ part is unused and in its original packaging.
Return procedure for MAX805LCSA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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