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Analog Devices Inc./Maxim Integrated MAX791EPE
- Part No.:
- MAX791EPE
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
MAX791EPE.pdf
- Description:
- IC SUPERVISOR MAX791 MPU
- Quantity:
- Payment:
- Shipping:
Inventory:1,750
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Product details
Overview
MAX791EPE from Maxim Integrated is a microprocessor supervisory circuit designed for power monitoring and battery switchover in embedded systems. It provides precision 4.65V reset threshold, 200ms reset timeout, 250mA VCC-mode output drive, 25mA battery-backup mode output, and independent watchdog timer with preset (1.6s) or adjustable timeout. It is used in portable/battery-powered equipment requiring reliable reset and power-fail warning.
For engineers reviewing the MAX791EPE datasheet, MAX791EPE pinout, MAX791EPE application, or MAX791EPE equivalent, key selection criteria include guaranteed RESET validity down to VCC = 1V, dual-stage power-fail detection (PFI/LOWLINE), CE signal gating with 6ns propagation delay, and battery-switchover hysteresis of 60mV.
Technical Context
The MAX791EPE integrates a precision voltage monitor, manual-reset input with 1.25V threshold, two-stage power-fail comparator (PFI at 1.25V, LOWLINE at 4.80V), and watchdog timer with internal 1.6s default timeout or external capacitor-adjustable period (4.7–100nF). Its battery-switchover logic activates when VCC falls below both the reset threshold (4.65V) and VBATT, with on-resistance of 13–25Ω in battery mode.
It features active-low open-drain outputs including RESET, WDO, WDPO, PFO, and LOWLINE, all pulled up to VOUT-not VCC-enabling valid operation during battery-backup mode. The CE gating function disables chip-enable propagation during reset assertion, with 75Ω series resistance and 6ns typical delay under 50Ω/50pF test conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 4.65V (typ), ±15mV tolerance; ensures deterministic µP reset at stable supply level |
| Reset Timeout | 200ms (typ); guarantees sufficient hold time after power-up or brownout recovery |
| VCC Supply Current | 50µA (typ) in normal mode; enables long battery life in portable applications |
| Battery-Backup Current | 1µA (max); minimizes drain on backup source during extended VCC loss |
| Output Drive (VCC mode) | 250mA sink capability on VOUT; supports direct driving of CMOS RAM or real-time clocks |
| Watchdog Timeout | 1.6s (preset) or adjustable via SWT capacitor (2.1 × CnF ms); provides flexible software fault detection window |
| CE Propagation Delay | 6ns (typ); preserves timing integrity for high-speed memory access during power transitions |
| Operating Temp Range | -40°C to +85°C; qualified for industrial and extended-temperature embedded deployments |
Pinout & Package
MAX791EPE is supplied in a 16-pin plastic DIP package (0.300" wide), RoHS-compliant and available in leaded or lead-free variants. Pin 1 is VBATT; pin 16 is WDPO. All pins are electrically defined per Maxim's official pin description table.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VBATT | Backup-battery input | Connects to external battery/capacitor; enables switchover when VCC drops below reset threshold and VBATT |
| 2 VOUT | Output supply voltage | Switches between VCC and VBATT; powers downstream logic (RAM, RTC) without external diodes |
| 3 VCC | Main supply input | +5V nominal input; monitored for reset, LOWLINE, and watchdog enable/disable logic |
| 4 GND | Ground reference | 0V return for all analog comparators, digital outputs, and internal bias networks |
| 5 BATT ON | Battery-on status indicator | Active-high open-drain output signaling VOUT is sourced from VBATT (not VCC) |
| 6 PFO | Power-fail output | Open-drain comparator output asserting low when PFI < 1.25V; usable as NMI or system alert |
| 7 PFI | Power-fail input | Non-inverting input to uncommitted comparator; monitors auxiliary supplies (e.g., -5V, +3.3V) via divider |
| 8 SWT | Watchdog timeout select | Connect to VOUT for 1.6s default; connect capacitor to GND for adjustable timeout (4.7–100nF) |
| 9 MR | Manual reset input | 1.25V threshold comparator input; accepts pushbutton or logic-level assertion; no external pull-up needed |
| 10 LOWLINE | Low-line comparator output | Asserts low when VCC falls to 150mV above reset threshold (≈4.80V); provides early brownout warning |
| 11 WDI | Watchdog input | Three-level input (high/mid/low); toggling resets watchdog timer; floating disables watchdog |
| 12 CE OUT | Chip-enable output | Gated version of CE IN; disabled during RESET to prevent memory corruption during power failure |
| 13 CE IN | Chip-enable input | High-impedance when RESET active; 75Ω series resistance when enabled; supports TTL/CMOS levels |
| 14 WDO | Watchdog output | Open-drain output asserting low after watchdog timeout; remains low until next WDI transition |
| 15 RESET | Reset output | Active-low open-drain output; guaranteed valid down to VCC = 1V; sinks 3.2mA @ 0.1V |
| 16 WDPO | Watchdog-pulse output | Pulses low for ≥1ms 70ns before WDO assertion; enables two-fault latching via external flip-flop |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed RESET validity to VCC = 1V | Enables robust reset behavior even during deep brownout; eliminates need for external pull-down in most designs |
| Two-stage power-fail detection | Separate PFI (1.25V) and LOWLINE (4.80V) comparators provide early warning and hard reset boundary |
| On-board CE signal gating | Prevents spurious memory writes during power transitions by disabling CE path when RESET is asserted |
| MaxCap®/SuperCap® compatible | Supports high-capacity backup capacitors (e.g., 0.47F) without external charge control circuitry |
| Independent watchdog with pulse output | WDPO enables hardware latching of consecutive faults; avoids reliance on software-only recovery |
| Battery-switchover hysteresis | 60mV hysteresis prevents oscillation during VCC/VBATT crossover; ensures clean mode transition |
Applications
| Portable Data Logger | Industrial PLC Controller |
|---|---|
Use Scenario: Battery-backed data acquisition unit logging sensor readings during mains outage. IC Role / Device Role / Timing Role: Supervises 5V rail, switches VOUT to VBATT upon mains loss, asserts RESET to halt µP, and pulses WDPO to trigger safe shutdown sequence. Use Value: Prevents data corruption during switchover; maintains RTC and RAM state for >24h on 2.8V coin cell; 1µA standby current extends battery life. | Use Scenario: Programmable logic controller operating in factory environment with fluctuating 24VDC supply. IC Role / Device Role / Timing Role: Monitors regulated 5V supply derived from 24VDC; uses LOWLINE to generate NMI on early brownout; asserts RESET if VCC drops below 4.65V. Use Value: Enables graceful I/O freeze and state save before full reset; 200ms timeout allows firmware to execute critical shutdown code. |
| Medical Infusion Pump | Point-of-Sale Terminal |
Use Scenario: Battery-powered infusion device requiring fail-safe operation and regulatory-compliant power monitoring. IC Role / Device Role / Timing Role: Provides redundant reset supervision; uses PFI to monitor auxiliary 3.3V rail; asserts PFO to disable motor drivers on power-fail event. Use Value: Dual-comparator architecture satisfies IEC 62304 safety requirements; 15µs PFI-to-PFO delay ensures timely response to supply collapse. | Use Scenario: Retail terminal with EEPROM-based configuration storage and real-time clock. IC Role / Device Role / Timing Role: Protects CMOS RAM and EEPROM during AC dropout; gates CE signals to prevent write cycles during unstable VCC; monitors battery health via software-readable PFI. Use Value: Eliminates need for discrete CE gating logic; 25mA battery-backup drive sustains RTC and RAM without external LDO. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX691ACPE+ | Same pinout, 4.65V reset, but lacks watchdog timer and CE gating; 100µA supply current vs. 50µA | No hardware fault detection or memory write protection; suitable only for basic reset-only use cases | Select MAX691ACPE+ only if watchdog and CE functions are unnecessary and cost is primary constraint |
| TPS3823MPW | 3-pin SOT-23 package, fixed 200ms reset timeout, no battery switchover or CE gating; 16µA quiescent current | Designed for space-constrained single-rail monitoring; cannot support backup-battery systems or memory protection | Choose TPS3823MPW for compact, low-power 5V-only monitoring where battery backup is absent |
Compared with MAX691ACPE+ and TPS3823MPW, the MAX791EPE uniquely combines precision reset, dual-stage power-fail warning, watchdog with pulse output, and CE signal gating in a single 16-pin DIP-making it the only option supporting battery-backed RAM retention, hardware fault latching, and memory write-cycle completion in industrial portable systems.
Availability
MAX791EPE is available at Aetrix Electronics and suitable for industrial PLC controllers, portable medical devices, battery-powered data loggers, and point-of-sale terminals requiring stable component supply across extended temperature ranges.
Supply support for MAX791EPE 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for industrial, automotive, and communications markets.
The MAX791 product line was engineered for microprocessor supervisory functions in battery-critical embedded systems-delivering integrated reset, watchdog, power-fail detection, and backup-switchover in a single chip to reduce board area and improve reliability.
FAQ
What is the guaranteed minimum operating voltage for RESET assertion in MAX791EPE?
The MAX791EPE guarantees valid RESET output down to VCC = 1V, even with no battery connected. This is achieved through internal biasing that maintains gate drive to the RESET output transistor. When using an external 10kΩ pull-down resistor on the RESET pin, the output saturation voltage remains below 0.4V while sinking 40µA, ensuring compatibility with µP reset inputs across the full VCC range. This specification is confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables of the MAX791EPE datasheet.
How does the MAX791EPE handle chip-enable (CE) signal gating during power failure?
The MAX791EPE disables the CE path during RESET assertion by turning off an internal 75Ω transmission gate between CE IN and CE OUT. In this state, CE OUT is actively pulled to VOUT, preventing spurious memory writes. The CE propagation delay is 6ns (typ) under standard test conditions (50Ω driver, 50pF load), and the gate re-enables only after RESET deassertion completes its 200ms timeout. This behavior is documented in the "Chip-Enable Signal Gating" section and verified in Figure 7 (Reset and Chip-Enable Timing) of the MAX791EPE datasheet.
Can the watchdog timeout period of MAX791EPE be adjusted, and what is the valid capacitor range?
Yes, the MAX791EPE watchdog timeout can be adjusted by connecting a capacitor between the SWT pin and GND. The timeout period equals 2.1 × CnF milliseconds, with valid values from 4.7nF to 100nF-yielding timeouts from ~10ms to ~210ms. Connecting SWT to VOUT selects the default 1.6s timeout. The formula and range are validated in the "Selecting an Alternative Watchdog-Timeout Period" section and the "Watchdog Timeout vs. Timing Capacitor" graph (Figure 11) of the MAX791EPE datasheet.
What is the function of the LOWLINE output in MAX791EPE, and how does it differ from RESET?
The LOWLINE output in MAX791EPE asserts low when VCC falls to 150mV above the 4.65V reset threshold (i.e., ~4.80V), providing early brownout warning before RESET activates. Unlike RESET-which holds for 200ms and halts µP execution-LOWLINE is intended for nonmaskable interrupt (NMI) generation to initiate graceful shutdown. Its 15mV hysteresis prevents chatter near threshold, and it sinks 3.2mA at 0.1V. This staged alerting is explicitly defined in the "LOWLINE Output" section and Figure 1 of the MAX791EPE datasheet.
Does MAX791EPE support backup-battery monitoring and switchover, and what are the key electrical parameters?
Yes, MAX791EPE supports automatic backup-battery switchover when VCC falls below both the reset threshold (4.65V) and VBATT. In battery-backup mode, VOUT connects to VBATT via an internal PMOS switch with on-resistance of 13–25Ω (typ), delivering up to 25mA continuous output. Battery standby current is ≤1µA, and switchover hysteresis is 60mV. These parameters are specified in the "Battery-Backup Mode" section and Table 1 ("Input and Output States in Battery-Backup Mode") of the MAX791EPE datasheet.
MAX791EPE Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Power Supply Monitor
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.65V
- Output:
- Open Drain or Open Collector
- Reset:
- Active Low
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
MAX791EPE FAQ
1.How can I place an order for MAX791EPE through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX791EPE 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 MAX791EPE reliable?
The price and inventory of MAX791EPE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX791EPE is usually 5 days.
3.What payment methods are accepted for MAX791EPE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX791EPE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX791EPE?
MAX791EPE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX791EPE 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 MAX791EPE?
For technical support, including MAX791EPE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX791EPE requirements.
6.How does Aetrix verify that MAX791EPE is sourced from the original manufacturer or authorized distributors?
All MAX791EPE 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 MAX791EPE meets industry standards.
7.What is the process for return or replacement of MAX791EPE?
All MAX791EPE units undergo pre-shipment inspection (PSI). If there is an issue with MAX791EPE, 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 MAX791EPE part is unused and in its original packaging.
Return procedure for MAX791EPE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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