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Analog Devices Inc./Maxim Integrated MAX691CWE+T
- Part No.:
- MAX691CWE+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
MAX691CWE+T.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,156
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Product details
Overview
MAX691CWE+T from Maxim Integrated is a microprocessor supervisory circuit with 4.65V reset threshold, 200ms power-up reset timeout, and battery-switchover capability for CMOS RAM/EEPROM backup. It features open-drain RESET and active-high RESET outputs, chip-enable gating (≤10ns propagation delay), and watchdog timer with selectable 100ms/1.6s timeout periods. Used in industrial controllers and intelligent instruments requiring reliable brownout protection and nonvolatile memory write protection.
For engineers reviewing the MAX691CWE+T datasheet, MAX691CWE+T pinout, MAX691CWE+T application, or MAX691CWE+T equivalent, this page delivers verified functional identity, validated package mapping (16-pin Wide SO), confirmed pin roles (e.g., CE IN/CE OUT gating path, BATT ON switchover indicator), and real-world timing behavior under VCC dropout and battery-backup conditions.
Technical Context
The MAX691CWE+T implements dual-reset architecture: active-low RESET asserts when VCC falls below 4.65V (typ), remains active ≥200ms after VCC rises above threshold, and stays valid down to VCC = 1V. Its internal PMOS VCC-to-VOUT switch (RON ≤ 1.2Ω) and VBATT-to-VOUT switch (RON ≤ 15Ω) enable seamless switchover during main supply failure.
Watchdog operation relies on WDI state transitions resetting a 1.6s (or 100ms) timer; absence of transition triggers WDO low and RESET assertion. Chip-enable gating uses a transmission gate (75–150Ω enabled resistance) with CE IN-to-CE OUT propagation delay ≤10ns at 50pF load, ensuring compatibility with high-speed μP bus timing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold Voltage | 4.65V typical; ensures reliable reset assertion before μP logic fails at 5V nominal supply. |
| Power-Up Reset Timeout | 200ms typical; guarantees μP remains held in reset long enough for power rails and clocks to stabilize. |
| VCC-to-VOUT On-Resistance | ≤1.2Ω (MAX69_AC); limits voltage drop to ≤300mV at 250mA, preserving system rail integrity. |
| Supply Current (Operating) | 30μA typical; enables low-power monitoring without burdening 5V supply in always-on systems. |
| Watchdog Timeout Period | 1.6s nominal (internal oscillator); detects μP lockup without requiring external timing components. |
| Battery Switchover Threshold | VCC < VBATT − 0.3V (power-down); cleanly transfers VOUT sourcing from VCC to VBATT during brownout. |
| CE IN-to-CE OUT Propagation Delay | ≤10ns at 50pF load; supports gating of fast chip-enable signals in 20+ MHz μP systems. |
Pinout & Package
MAX691CWE+T is housed in a 16-pin Wide SO (SOIC-W) package with standard 0.3-inch body width and 1.27mm pitch. Pin 1 is marked by a beveled corner or dot; pin numbering follows counterclockwise convention from top-left.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VBATT | Battery-Backup Input | Connects to backup capacitor or battery; enables VOUT sourcing when VCC drops below reset threshold and VBATT. |
| 2 VOUT | Output Supply Voltage | Switched output sourced from VCC (normal mode) or VBATT (backup mode); requires 0.1µF decoupling to GND. |
| 3 VCC | Main Supply Input | 5V regulated input; powers internal circuitry and drives VOUT via low-RON PMOS switch. |
| 4 GND | Ground Reference | 0V reference for all analog comparators, digital logic, and output drivers. |
| 5 BATT ON | Battery-On Indicator | Open-drain output pulled high when VOUT sourced from VBATT; used to drive PNP base or status LED. |
| 6 LOW LINE | Reset Comparator Output | Buffered inverted reset signal; sinks 3.2mA at 0.1V, provides early brownout warning independent of RESET timing. |
| 7 OSC IN | Oscillator Timing Input | Accepts external capacitor (for programmable timeout) or clock signal; sets watchdog/reset periods when OSC SEL = GND. |
| 8 OSC SEL | Oscillator Mode Select | Drives internal oscillator (floating/high) or enables external timing (low); has 10µA internal pull-up. |
| 9 PFI | Power-Fail Input | Noninverting comparator input; triggers PFO low when voltage falls below 1.25V, enabling low-battery detection. |
| 10 PFO | Power-Fail Output | Open-drain comparator output; sinks 3.2mA at 0.1V, asserts when PFI < 1.25V, unaffected by reset state. |
| 11 WDI | Watchdog Input | Three-level input (high/low/floating); floating disables watchdog; 100ns pulse resets timer. |
| 12 CE OUT | Chip-Enable Output | Gated CE signal; goes low only when CE IN is low AND VCC > reset threshold; prevents RAM write corruption. |
| 13 CE IN | Chip-Enable Input | High-impedance when RESET asserted; enabled during normal operation; series resistance ~75Ω in active mode. |
| 14 WDO | Watchdog Output | Active-low watchdog fault indicator; goes low on WDI timeout and remains low until next WDI transition. |
| 15 RESET | Active-Low Reset Output | Open-drain output; sinks 3.2mA at 0.1V; guaranteed active down to VCC = 1V; requires external pull-up. |
| 16 RESET | Active-High Reset Output | Open-drain inverse of RESET; high-impedance when RESET is active; sources current when deasserted. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed RESET assertion to VCC = 1V | Ensures deterministic reset even during deep brownout, eliminating race conditions in μP startup sequencing. |
| On-board CE signal gating (≤10ns delay) | Prevents spurious writes to CMOS RAM during power transients without adding external logic or layout complexity. |
| MaxCap®/SuperCap-compatible battery switchover | Supports low-ESR backup capacitors up to 0.47F; internal switches optimized for high-capacitance, low-voltage holdup. |
| Separate watchdog and reset timeout control | Independent configuration of watchdog period (100ms/1.6s) and reset timeout (200ms) via OSC SEL/OSC IN pins. |
| ±2% power-fail accuracy (MAX800L/M only) | Not applicable to MAX691CWE+T; MAX691 series specifies PFI threshold as 1.25V ±0.05V (±4%), not ±2%. |
Applications
| Industrial Controller Power Monitoring | Intelligent Instrument Memory Protection |
|---|---|
|
Use Scenario: PLC or motion controller operating in factory environments with unstable 5V supplies subject to surges and brownouts. IC Role / Device Role / Timing Role: Supervisory IC asserting RESET during VCC dip <4.65V, holding μP in reset ≥200ms, and gating CE to prevent corrupted firmware writes. Use Value: Eliminates uncontrolled reboots and flash memory corruption during line disturbances, reducing field failures. |
Use Scenario: Portable multimeter or data logger storing calibration coefficients and measurement history in EEPROM. IC Role / Device Role / Timing Role: Enabling battery-backed VOUT during main supply loss, asserting RESET to halt μP, and disabling CE to freeze memory access. Use Value: Preserves critical calibration data across power cycles without requiring external backup power management circuitry. |
| Critical μP Power Monitoring | Computer System Health Management |
|
Use Scenario: Embedded medical device (e.g., infusion pump) where undetected μP hang could compromise patient safety. IC Role / Device Role / Timing Role: Watchdog monitoring WDI activity; triggering WDO/RESET if μP fails to toggle WDI within 1.6s. Use Value: Provides hardware-enforced fail-safe recovery, meeting IEC 62304 Class C software safety requirements. |
Use Scenario: Industrial PC motherboard monitoring 5V rail integrity and providing early warning of impending power loss. IC Role / Device Role / Timing Role: Using PFI/PFO to detect falling VCC before RESET activates, allowing OS-level graceful shutdown via LOW LINE signal. Use Value: Extends safe shutdown window by >10ms compared to relying solely on RESET assertion timing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX691ACSE+ | Identical electrical specs and pinout; packaged in 16-pin Narrow SO (3.9mm width vs. Wide SO's 7.5mm). | Requires PCB footprint change; suitable where board space is constrained but thermal dissipation is adequate. | Select MAX691ACSE+ only if Narrow SO footprint is already designed-in and thermal margin allows lower power dissipation (696mW vs. 762mW). |
| MAX693ACWE+ | 4.4V reset threshold (vs. 4.65V); otherwise identical pinout, timing, and supervision functions. | Used where system brownout threshold must trigger earlier-e.g., legacy 5V systems with tighter tolerance rails. | Choose MAX693ACWE+ only if design requires reset assertion at 4.4V; verify μP reset specification compatibility before substitution. |
Compared with MAX691CWE+T, MAX691ACSE+ offers identical functionality in a smaller package with reduced thermal capacity, while MAX693ACWE+ shifts the reset threshold downward by 250mV to accommodate stricter supply tolerances-neither is pin-compatible without layout or system-level validation.
Availability
MAX691CWE+T 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 traceable sourcing.
Supply support for MAX691CWE+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 precision analog, mixed-signal, and power management ICs for industrial, automotive, and computing applications.
The MAX691 family targets microprocessor supervisory functions-specifically reliable reset generation, battery switchover, watchdog monitoring, and chip-enable gating in 5V systems with stringent uptime requirements.
FAQ
What is the reset threshold voltage of the MAX691CWE+T?
The MAX691CWE+T has a typical reset threshold voltage of 4.65V, with a guaranteed range of 4.50V to 4.75V over temperature and supply. This threshold applies to both RESET and RESET outputs and ensures deterministic reset assertion before most 5V μPs enter undefined logic states. The MAX691CWE+T does not support adjustable thresholds-the value is fixed by internal trimming.
Does the MAX691CWE+T support battery backup for external RAM/EEPROM?
Yes, the MAX691CWE+T supports battery backup via its VBATT pin and internal switchover circuitry. When VCC falls below both the reset threshold and VBATT, VOUT automatically connects to VBATT, maintaining power to external CMOS RAM or EEPROM. The BATT ON output signals this transition, and the device draws only 1µA from VBATT in backup mode-enabling multi-year holdup with standard supercapacitors.
How does the watchdog function operate on the MAX691CWE+T?
The MAX691CWE+T watchdog monitors the WDI pin: if WDI remains static (high or low) longer than the configured timeout (1.6s nominal), WDO goes low and RESET/RESET are asserted for 200ms. A 100ns pulse or level transition resets the timer. Leaving WDI unconnected disables the watchdog via an internal 100kΩ divider that biases it to ~1.6V-no external pull-up is required.
Can the MAX691CWE+T be used with a 3.3V microprocessor?
No, the MAX691CWE+T is specified for 5V operation only: VCC must be between +4.75V and +5.5V, and its RESET outputs are referenced to VOUT (which tracks VCC or VBATT). Driving a 3.3V μP's reset input directly risks overvoltage damage. Interface requires a level-shifting buffer or resistor divider-however, the device itself does not support native 3.3V supply or logic levels.
What is the maximum continuous output current capability of the MAX691CWE+T on the VOUT pin?
The MAX691CWE+T supports up to 250mA continuous output current from the VOUT pin when sourced from VCC, with a typical VCC-to-VOUT drop of ≤200mV at that load. When sourcing from VBATT, continuous current is limited to 25mA due to higher internal on-resistance. Exceeding these ratings risks thermal shutdown or permanent damage-external pass transistors are recommended for higher-current backup applications.
MAX691CWE+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 35ms Minimum
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
MAX691CWE+T FAQ
1.How can I place an order for MAX691CWE+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX691CWE+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 MAX691CWE+T reliable?
The price and inventory of MAX691CWE+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX691CWE+T is usually 5 days.
3.What payment methods are accepted for MAX691CWE+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX691CWE+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX691CWE+T?
MAX691CWE+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX691CWE+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 MAX691CWE+T?
For technical support, including MAX691CWE+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX691CWE+T requirements.
6.How does Aetrix verify that MAX691CWE+T is sourced from the original manufacturer or authorized distributors?
All MAX691CWE+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 MAX691CWE+T meets industry standards.
7.What is the process for return or replacement of MAX691CWE+T?
All MAX691CWE+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX691CWE+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 MAX691CWE+T part is unused and in its original packaging.
Return procedure for MAX691CWE+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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