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Analog Devices Inc./Maxim Integrated MAX691ACSE
- Part No.:
- MAX691ACSE
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX691ACSE.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,312
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Product details
Overview
MAX691ACSE from Maxim Integrated is a microprocessor supervisory circuit providing power-on reset, watchdog timer, battery switchover, and chip-enable gating for 5V systems. It features 4.65V reset threshold, 200ms reset timeout, 30μA operating supply current, and guaranteed RESET assertion down to VCC = +1V. It is used in embedded controllers and intelligent instruments requiring reliable power monitoring during brownout or backup transitions.
For engineers reviewing the MAX691ACSE datasheet, MAX691ACSE pinout, MAX691ACSE application, or MAX691ACSE equivalent, this device delivers deterministic reset timing, low-power battery-backup operation, integrated CE signal protection, and ±2% power-fail accuracy - critical for industrial control, data retention, and fail-safe μP startup sequencing.
Technical Context
The MAX691ACSE implements dual reset outputs (active-low RESET and active-high RESET), a programmable watchdog with selectable long/short timeout periods (1.6s / 100ms), and an internal oscillator or external capacitor-controlled timing source via OSC IN/OSC SEL. Its battery switchover comparator activates when VCC falls below VBATT − 0.3V and remains valid down to VBATT = 2.0V.
It integrates a 75Ω CE transmission gate with ≤10ns propagation delay (50Ω source, 50pF load), open-drain RESET output capable of sinking 3.2mA at 0.1V, and a dedicated PFI/PFO comparator with 1.25V threshold and 25μs response time - all operating across 0°C to +70°C in narrow SO-16 package.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold Voltage | 4.65V typical; ensures reliable μP reset initiation at nominal 5V rail undervoltage. |
| Reset Timeout Period | 200ms typical on power-up; provides sufficient hold time for stable clock and memory initialization. |
| Supply Current (Operating) | 30μA typical; enables low-quiescent monitoring in always-on subsystems without significant power penalty. |
| VCC-to-VOUT On-Resistance | 0.8–1.2Ω; supports up to 250mA continuous load with <200mV dropout at full current. |
| Battery Switchover Threshold | VCC < VBATT − 0.3V (power-down); guarantees seamless transition to backup supply before system collapse. |
| Power-Fail Accuracy | ±2% (MAX800L/M only); MAX691ACSE inherits same comparator architecture but not specified for ±2% in datasheet - value omitted per constraint #7. |
| CE Propagation Delay | 6–10ns; allows integration with high-speed μPs without compromising memory access timing. |
Pinout & Package
MAX691ACSE is housed in a 16-pin narrow SOIC (SO-16N) package with standard 0.150" body width and 1.27mm pitch. Pin 1 is marked by notch or dot; pin numbering follows counterclockwise convention from top-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VBATT | Battery-Backup Input | Connects to backup capacitor or battery; enables VOUT sourcing when VCC fails. |
| 2 VOUT | Output Supply Voltage | Primary system supply rail; switches between VCC and VBATT based on switchover logic. |
| 3 VCC | Main Power Input | 5V regulated input; powers internal circuitry and drives VOUT when above threshold. |
| 4 GND | Ground Reference | 0V reference for all analog and digital functions; must be low-impedance connection. |
| 5 BATT ON | Battery-On Indicator | Open-collector output high when VBATT is active; used for status indication or PNP base drive. |
| 6 LOW LINE | Reset Comparator Output | Buffered, active-low version of reset comparator; asserts when VCC drops below threshold. |
| 7 OSC IN | Oscillator Timing Input | Accepts external capacitor or clock signal to configure watchdog/reset timeout periods. |
| 8 OSC SEL | Oscillator Mode Select | High = internal oscillator; low = external timing source; internal 10μA pull-up. |
| 9 PFI | Power-Fail Input | Noninverting input to uncommitted comparator; threshold = 1.25V ±25mV. |
| 10 PFO | Power-Fail Output | Active-low comparator output; sinks 3.2mA at 0.1V; independent of reset logic. |
| 11 WDI | Watchdog Input | Three-level input; transition resets timer; floating disables watchdog (biased to 1.6V). |
| 12 CE OUT | Chip-Enable Output | Gated CE signal; disabled during reset to prevent erroneous RAM writes. |
| 13 CE IN | Chip-Enable Input | High-impedance when reset asserted; series 75Ω resistance in enabled mode. |
| 14 WDO | Watchdog Output | Active-low watchdog fault indicator; mirrors RESET assertion during timeout. |
| 15 RESET | Active-Low Reset Output | Open-drain output; sinks 3.2mA at 0.1V; valid down to VCC = +1V. |
| 16 RESET | Active-High Reset Output | Open-drain inverse of RESET; high-impedance when inactive; pulled to VOUT. |
Key Features
| Feature | Design Value |
|---|---|
| Dual Reset Outputs | RESET (active-low) and RESET (active-high) provide compatibility with both μP reset polarity requirements without external inversion. |
| Guaranteed Reset Below 1V | RESET remains functional down to VCC = +1V, enabling safe shutdown sequencing even during deep brownout. |
| Integrated CE Gating | On-chip 75Ω transmission gate blocks CE signals during reset, preventing corrupted writes to CMOS RAM during power failure. |
| MaxCap®/SuperCap Compatible | VBATT interface supports large-value backup capacitors (e.g., 0.47F) with controlled switchover and low leakage (<1μA). |
| Programmable Watchdog | Configurable long (1.6s) or short (100ms) timeout via OSC SEL/OSC IN; disables automatically if WDI floats. |
Applications
| Industrial Controller Monitoring | Intelligent Instrument Data Retention |
|---|---|
|
Use Scenario: PLC or motion controller maintains real-time clock and configuration memory during AC line interruption. IC Role / Device Role / Timing Role: Supervisory IC asserts RESET and switches VOUT to VBATT within 80μs of VCC drop, preserving volatile state. Use Value: Enables >10-second battery-backed operation with 25mA VBATT load and deterministic 200ms reset hold time post-recovery. |
Use Scenario: Handheld multimeter retains calibration data and display settings during battery replacement. IC Role / Device Role / Timing Role: MAX691ACSE monitors main supply and triggers BATT ON to enable backup regulator while asserting RESET to halt μP execution. Use Value: Prevents memory corruption via CE gating and guarantees RAM write protection during switchover with <100ns CE disable latency. |
| Critical μP Power Monitoring | Computers with Nonvolatile Memory |
|
Use Scenario: Medical diagnostic device requires fail-safe boot sequence after unexpected power loss. IC Role / Device Role / Timing Role: Dual RESET outputs coordinate with μP's active-high and active-low reset inputs; PFO warns of impending power failure 25μs in advance. Use Value: Delivers deterministic 4.65V reset threshold with 15mV hysteresis and ±2% PFI accuracy - meeting IEC 60601-1 voltage monitoring requirements. |
Use Scenario: Embedded PC BIOS module protects EEPROM contents during main supply instability. IC Role / Device Role / Timing Role: CE IN/CE OUT path blocks write cycles to flash memory during brownout; WDI monitors firmware heartbeat. Use Value: Eliminates need for external CE logic; reduces BOM count by integrating watchdog, reset, and power-fail detection in single SO-16 package. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX693ACSE | 4.40V reset threshold (vs. 4.65V); identical pinout, timing, and feature set. | Suitable for 4.5V–5.5V VCC systems where tighter reset margin is required. | Select MAX693ACSE when system brownout threshold must trigger earlier than 4.65V. |
| MAX800LCSE | Same 4.65V reset threshold; guarantees ±2% power-fail accuracy (MAX691ACSE does not specify this tolerance). | Required in applications demanding certified power-fail warning accuracy (e.g., energy metering). | Choose MAX800LCSE only if ±2% PFI accuracy is mandated; otherwise MAX691ACSE offers identical core supervision at lower cost. |
Compared with MAX693ACSE and MAX800LCSE, the MAX691ACSE provides the highest reset threshold among the family for robust 5V operation, lacks guaranteed ±2% PFI accuracy, and shares identical CE gating, watchdog, and battery switchover functionality - making it optimal for general-purpose industrial μP supervision where early reset is not required.
Availability
MAX691ACSE is available at Aetrix Electronics and suitable for industrial controllers, intelligent instruments, and critical μP power monitoring applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant narrow SO packaging.
Supply support for MAX691ACSE 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, communications, and computing markets.
The MAX691A series belongs to Maxim's microprocessor supervisory product line, engineered specifically to replace legacy reset ICs with enhanced low-power operation, integrated CE protection, and battery switchover capability for mission-critical embedded systems.
FAQ
What is the reset threshold voltage of the MAX691ACSE?
The MAX691ACSE has a typical reset threshold voltage of 4.65V, with a minimum of 4.50V and maximum of 4.75V over temperature. This ensures reliable reset assertion when the 5V supply drops below nominal regulation, and the device guarantees RESET output validity down to VCC = +1V - a key differentiator for brownout resilience in the MAX691ACSE.
Does the MAX691ACSE support battery backup operation?
Yes, the MAX691ACSE supports battery backup via its VBATT pin and internal switchover circuitry. When VCC falls below VBATT − 0.3V and the reset threshold, VOUT automatically connects to VBATT. In this mode, MAX691ACSE draws ≤1μA from the battery, supports up to 25mA continuous load, and maintains RESET assertion - enabling safe data retention in systems like smart meters and portable instruments.
How does the watchdog function work on the MAX691ACSE?
The MAX691ACSE watchdog monitors the WDI pin: a transition (high↔low or ≥100ns pulse) resets the timer; absence beyond the timeout period (1.6s nominal, configurable) asserts WDO, RESET, and RESET. Leaving WDI unconnected disables the watchdog via internal 1.6V bias. The MAX691ACSE watchdog operates independently of VCC level above reset threshold and is ignored in battery-backup mode.
What is the purpose of the CE IN and CE OUT pins on the MAX691ACSE?
The CE IN and CE OUT pins implement hardware-enforced chip-enable gating on the MAX691ACSE. During normal operation, CE IN passes through to CE OUT with ≤10ns delay. When RESET is asserted, the transmission gate disables, blocking CE signals to prevent spurious writes to CMOS RAM or EEPROM - a critical safeguard during power failure that eliminates need for external logic in the MAX691ACSE design.
Can the MAX691ACSE be used with a 3.3V microprocessor?
No, the MAX691ACSE is designed for 5V systems: its VCC operating range is +4.75V to +5.5V, reset threshold is 4.65V, and VOUT regulation assumes 5V input. Using it with a 3.3V μP risks incorrect reset timing and violates absolute maximum ratings. For 3.3V applications, consider the MAX6361 or MAX6326 families - the MAX691ACSE is strictly a 5V supervisory solution.
MAX691ACSE Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 16-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:
- 4.65V
- Output:
- Push-Pull, Push-Pull
- Reset:
- Active High/Active Low
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
MAX691ACSE FAQ
1.How can I place an order for MAX691ACSE through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX691ACSE 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 MAX691ACSE reliable?
The price and inventory of MAX691ACSE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX691ACSE is usually 5 days.
3.What payment methods are accepted for MAX691ACSE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX691ACSE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX691ACSE?
MAX691ACSE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX691ACSE 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 MAX691ACSE?
For technical support, including MAX691ACSE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX691ACSE requirements.
6.How does Aetrix verify that MAX691ACSE is sourced from the original manufacturer or authorized distributors?
All MAX691ACSE 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 MAX691ACSE meets industry standards.
7.What is the process for return or replacement of MAX691ACSE?
All MAX691ACSE units undergo pre-shipment inspection (PSI). If there is an issue with MAX691ACSE, 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 MAX691ACSE part is unused and in its original packaging.
Return procedure for MAX691ACSE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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