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Analog Devices Inc./Maxim Integrated MAX691ACWE+
- Part No.:
- MAX691ACWE+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
MAX691ACWE+.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:694
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Product details
Overview
MAX691ACWE+ from Maxim Integrated is a microprocessor supervisory circuit designed for 5V systems, providing power-on reset, watchdog timer, battery switchover, and chip-enable gating. It features a 4.65V typical 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 and data retention during brownout.
For engineers reviewing the MAX691ACWE+ datasheet, MAX691ACWE+ pinout, MAX691ACWE+ application, or MAX691ACWE+ equivalent, key selection criteria include reset threshold accuracy (±15mV hysteresis), battery switchover behavior (VVBATT ±0.3V thresholds), CE propagation delay (6–10ns), PFI comparator precision (±2% at 1.25V), and compatibility with MaxCap/supercapacitor backup schemes.
Technical Context
The MAX691ACWE+ integrates a precision voltage monitor, dual-reset outputs (active-low RESET and active-high RESET), a programmable watchdog timer with internal/external timing options, and bidirectional CE signal gating. Its reset generator uses an internal oscillator with 200ms typical power-up delay and 80μs power-down response.
It implements automatic battery switchover via a dedicated comparator that enables VBATT-to-VOUT conduction when VCC falls below VBATT − 0.3V, while maintaining BATT ON status indication and supporting up to 25mA continuous battery current. The PFI/PFO comparator operates independently with 1.25V threshold and ±25nA input leakage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold Voltage | 4.65V typical; ensures reliable μP reset initiation at nominal 5V rail drop, with 15mV hysteresis to prevent chatter. |
| Reset Timeout Period | 200ms typical (power-up); guarantees sufficient hold time for μP initialization before release. |
| Supply Current (Operating) | 30μA typical; enables low-power system monitoring without burdening main 5V rail. |
| VCC-to-VOUT On-Resistance | 0.8–1.2Ω (MAX69_AC); maintains <200mV dropout at 250mA load, preserving logic-level margins. |
| Battery Switchover Threshold | VCC < VBATT − 0.3V (power-down); triggers seamless transition to backup source before VCC crosses reset threshold. |
| PFI Comparator Accuracy | ±2% over temperature; supports precise early power-fail warning or low-battery detection at 1.25V reference. |
| CE Propagation Delay | 6–10ns (50Ω source, 50pF load); compatible with high-speed μP bus timing without added latency. |
Pinout & Package
MAX691ACWE+ is housed in a 16-pin Wide SO (SOIC-W) package, 7.5mm × 10.3mm body, 1.27mm pitch, RoHS-compliant lead-free finish (indicated by '+' suffix).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VBATT | Battery-Backup Input | Connects to backup capacitor/battery; enables switchover when VCC drops below VBATT − 0.3V. |
| 2 VOUT | Output Supply Voltage | Primary system supply output; sourced from VCC or VBATT depending on switchover state. |
| 3 VCC | Main 5V Supply Input | Regulated 4.75–5.5V input; powers internal circuitry and drives VOUT via low-RDS(ON) PMOS switch. |
| 4 GND | Ground Reference | 0V return for all analog/digital functions; decoupling capacitor must connect here and to VOUT. |
| 5 BATT ON | Battery-On Status Output | Open-drain logic-high indicator during battery-backup mode; usable for external pass transistor control. |
| 6 LOW LINE | Reset Comparator Buffer | Active-low buffered version of reset comparator output; sinks 3.2mA at 0.1V for direct LED/interface use. |
| 7 OSC IN | External Timing Input | Accepts capacitor or clock signal to configure watchdog/reset timeout periods; internally biased at 1.6V if floating. |
| 8 OSC SEL | Oscillator Mode Select | High = internal oscillator (1.6s/200ms defaults); low = external timing via OSC IN; 10μA internal pull-up. |
| 9 PFI | Power-Fail Input | Non-inverting input to uncommitted comparator; threshold fixed at 1.25V ±2% for accurate low-VCC detection. |
| 10 PFO | Power-Fail Output | Open-drain comparator output; asserts low when PFI < 1.25V; independent of reset/watchdog logic. |
| 11 WDI | Watchdog Input | Three-level input (high/low/floating); resets watchdog timer on edge/pulse ≥100ns; floating disables function. |
| 12 CE OUT | Chip-Enable Output | Gated CE signal; disabled during reset to prevent spurious writes to CMOS RAM/EEPROM. |
| 13 CE IN | Chip-Enable Input | High-impedance input during reset; series 75Ω resistance in enabled mode; leakage ≤±1μA. |
| 14 WDO | Watchdog Output | Active-low watchdog fault indicator; goes low on timeout and remains low until next WDI transition. |
| 15 RESET | Active-Low Reset Output | Open-drain output; sinks 3.2mA at 0.1V; valid down to VCC = 1V; requires external pull-up for μP reset input. |
| 16 RESET | Active-High Reset Output | Open-drain inverse of RESET; high-impedance when inactive; driven low synchronously with RESET. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed RESET validity to VCC = 1V | Enables robust reset assertion even during deep brownout, critical for fail-safe μP shutdown sequences. |
| On-board CE signal gating (10ns max delay) | Prevents erroneous memory writes during power failure without external logic or timing-critical PCB routing. |
| MaxCap®/supercapacitor-compatible backup | Supports low-ESR, high-capacitance backup sources with controlled switchover and minimal voltage droop. |
| Dual independent reset outputs (RESET/RESET) | Provides both active-low and active-high reset signals to match diverse μP interface requirements without level-shifting. |
| Independent PFI/PFO comparator | Allows configurable early power-fail warning or low-battery alert without interfering with core reset/watchdog operation. |
Applications
| Industrial Controller Monitoring | Embedded Data Logger |
|---|---|
|
Use Scenario: PLC or motion controller operating in factory environments with fluctuating 5V rails and need for deterministic restart after brownout. IC Role / Device Role / Timing Role: Supervisory IC providing synchronized reset, watchdog supervision, and CE gating to protect firmware execution and nonvolatile memory writes. Use Value: Prevents corrupted configuration storage during undervoltage events and ensures μP boots only after stable 5V is confirmed for ≥200ms. |
Use Scenario: Battery-backed environmental sensor node logging data to EEPROM during mains loss. IC Role / Device Role / Timing Role: Power supervisor managing VCC/VBATT switchover, asserting RESET to halt μP, and enabling backup power path before VCC collapse. Use Value: Guarantees clean shutdown and preserves last valid sensor readings using 25mA battery current capability and 1μA standby draw. |
| Medical Diagnostic Instrument | Point-of-Sale Terminal |
|
Use Scenario: Portable ultrasound or ECG device requiring FDA-grade power integrity and no unintended reboots during battery swap. IC Role / Device Role / Timing Role: Dual-reset supervisor with independent PFO alarm and BATT ON status signaling for user-facing battery-switchover indication. Use Value: Enables safe hot-swap of backup battery while maintaining real-time data buffer integrity via VOUT hold-up and CE disable. |
Use Scenario: Retail terminal with flash memory storing transaction logs and requiring write-protection during AC power interruption. IC Role / Device Role / Timing Role: Memory protection supervisor using CE gating and watchdog-triggered reset to abort incomplete writes before power loss. Use Value: Eliminates flash corruption risk by disabling CE within 15μs of reset assertion and holding reset for full 200ms timeout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX691AEWE+ | Wider temperature range (−40°C to +85°C); identical electrical specs and pinout. | Suitable for industrial/outdoor deployments where ambient exceeds 70°C. | Select MAX691AEWE+ when extended temperature operation is required; otherwise MAX691ACWE+ suffices for commercial environments. |
| TPS3808G33DBVR | Fixed 3.3V reset threshold; no battery switchover, CE gating, or watchdog; lower quiescent current (1.5μA). | Limited to single-rail 3.3V systems without backup power or memory write protection needs. | Choose TPS3808G33DBVR only for cost-sensitive 3.3V-only designs omitting battery backup and CE control. |
Compared with MAX691AEWE+, the MAX691ACWE+ offers identical functionality at lower cost for 0°C to +70°C operation, while the TPS3808G33DBVR lacks battery switchover, watchdog, and CE gating-making it unsuitable as a functional replacement despite shared supervisory purpose.
Availability
MAX691ACWE+ is available at Aetrix Electronics and suitable for industrial controllers, embedded data loggers, medical diagnostic instruments, and point-of-sale terminals requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for MAX691ACWE+ 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, communications, and computing applications.
The MAX691A family was designed specifically for robust 5V microprocessor supervision-integrating reset, watchdog, battery switchover, and memory write protection in a single 16-pin package for space-constrained embedded systems.
FAQ
What is the reset threshold voltage of the MAX691ACWE+ and how does it behave across temperature?
The MAX691ACWE+ has a typical reset threshold voltage of 4.65V, with a minimum of 4.50V and maximum of 4.75V over the 0°C to +70°C operating range. Its hysteresis is 15mV, preventing oscillation near the trip point. The threshold drifts less than ±15mV across temperature, as confirmed by Figure MAX691A toc07 in the datasheet, ensuring consistent reset behavior in commercial environments.
Does the MAX691ACWE+ support battery backup, and what are the voltage conditions for switchover?
Yes, the MAX691ACWE+ supports automatic battery backup via its VBATT input. Switchover occurs when VCC falls below VBATT − 0.3V (power-down) or rises above VBATT + 0.3V (power-up), with 60mV hysteresis. In battery-backup mode, VOUT is sourced from VBATT, BATT ON goes high, and RESET remains asserted until VCC recovers-ensuring uninterrupted operation during mains loss.
How does the CE gating function work on the MAX691ACWE+, and what is its propagation delay?
The MAX691ACWE+ gates the CE signal between CE IN and CE OUT using an internal transmission gate. During normal operation, CE transitions pass through with ≤10ns propagation delay (tested at 50Ω source, 50pF load). When RESET is asserted, CE OUT is disabled within 15μs, blocking spurious memory writes-a critical feature for protecting CMOS RAM during power faults.
Can the MAX691ACWE+ watchdog timer be disabled, and how is that accomplished?
Yes, the MAX691ACWE+ watchdog can be disabled by leaving the WDI pin unconnected. An internal 100kΩ resistor network biases WDI to ~1.6V, which the internal comparators recognize as a disabled state. When VCC drops below the reset threshold, the watchdog is automatically disabled regardless of WDI state-ensuring safe behavior during power failure.
What is the purpose of the PFI/PFO pins on the MAX691ACWE+, and are they tied to the reset function?
The PFI/PFO pins form an independent, uncommitted comparator with a fixed 1.25V threshold and ±2% accuracy. PFO asserts low when PFI falls below 1.25V, enabling early power-fail warning or low-battery detection. Critically, this comparator operates entirely separately from the reset generator, watchdog, and CE logic-so PFI activity never affects RESET timing or system reset behavior.
MAX691ACWE+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 16-SOIC (0.295", 7.50mm 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, 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
MAX691ACWE+ FAQ
1.How can I place an order for MAX691ACWE+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX691ACWE+ 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 MAX691ACWE+ reliable?
The price and inventory of MAX691ACWE+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX691ACWE+ is usually 5 days.
3.What payment methods are accepted for MAX691ACWE+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX691ACWE+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX691ACWE+?
MAX691ACWE+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX691ACWE+ 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 MAX691ACWE+?
For technical support, including MAX691ACWE+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX691ACWE+ requirements.
6.How does Aetrix verify that MAX691ACWE+ is sourced from the original manufacturer or authorized distributors?
All MAX691ACWE+ 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 MAX691ACWE+ meets industry standards.
7.What is the process for return or replacement of MAX691ACWE+?
All MAX691ACWE+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX691ACWE+, 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 MAX691ACWE+ part is unused and in its original packaging.
Return procedure for MAX691ACWE+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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