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Analog Devices Inc./Maxim Integrated MAX691CWE
- Part No.:
- MAX691CWE
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
MAX691CWE.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,997
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Product details
Overview
MAX691CWE from Maxim Integrated is a 16-pin microprocessor supervisory circuit providing reset generation, battery backup switchover, watchdog timer, power-fail detection, and CE gating for CMOS RAM. It features a 4.65V reset threshold, 200ms reset timeout, 1.6s/100ms selectable watchdog, 1.3V PFI comparator, and VOUT switching between VCC and VBATT. It is used in industrial controllers and intelligent instruments requiring reliable power monitoring and data retention during brownouts.
For engineers reviewing the MAX691CWE datasheet, MAX691CWE pinout, MAX691CWE application, or MAX691CWE equivalent, key selection considerations include its 16-pin SOIC-W package, active-low RESET with 200ms delay, dual-mode watchdog (internal oscillator or external clock), CE OUT write-protection logic, and battery switchover hysteresis of 20mV - all critical for embedded µP system integrity.
Technical Context
The MAX691CWE integrates five core supervisory functions in a single IC: precision voltage monitoring (4.65V ±150mV threshold), programmable reset timing (200ms default), adjustable watchdog timeout (100ms or 1.6s via OSC SEL/OSC IN), battery-backed VOUT switching with 200Ω MOSFET, and CE IN/CE OUT gating to prevent erroneous RAM writes during low-VCC events.
Its architecture includes an internal 6.55kHz oscillator, three-level WDI input (low/mid/high) enabling watchdog disable via floating state, BATT ON output for external PNP drive, LOW LINE for immediate VCC-fall indication, and PFO tied to a dedicated 1.3V reference for early power-fail warning - all operating across –40°C to +85°C (E-suffix).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 4.65V (min 4.5V, max 4.75V); ensures reliable reset assertion before µP operation becomes unstable under 5V ±5% supply tolerance. |
| Reset Timeout Delay | 200ms (typical); holds RESET low long enough for crystal oscillator startup and µP initialization after power-up. |
| Watchdog Timeout | Selectable 100ms or 1.6s; prevents software lockup by forcing reset if WDI is not toggled within configured window. |
| VOUT Switching | Connects higher of VCC or VBATT to VOUT; enables seamless CMOS RAM backup when VCC drops below VBATT − 70mV (rise) or VBATT − 50mV (fall). |
| PFI Comparator Threshold | 1.3V (±0.1V); allows configurable early power-fail warning via external resistor divider on unregulated or regulated rails. |
| Battery Standby Current | 1µA max (VCC = 0V, VBATT = 2.8V); extends lithium or coin-cell life during extended backup mode. |
| CE Propagation Delay | 50–200ns; ensures rapid CE OUT deactivation when VCC falls below reset threshold, blocking RAM writes before µP enters invalid state. |
Pinout & Package
MAX691CWE is housed in a 16-pin wide-body SOIC (SOIC-W) package, 7.5mm body width, 1.27mm pitch, RoHS-compliant, rated for –40°C to +85°C operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | VCC | +5V main supply input; powers internal circuitry and sources VOUT when above VBATT. |
| 2 | VBATT | Backup battery input (2.0V–4.25V); supplies VOUT when VCC fails or drops below switchover threshold. |
| 3 | VOUT | Switched output; delivers higher of VCC or VBATT to CMOS RAM; rated for 50mA continuous, short-circuit protected. |
| 4 | GND | Ground reference for all analog and digital functions; must be low-impedance connection. |
| 5 | RESET | Active-low reset output; asserts low for 200ms after VCC rises above 4.65V or watchdog timeout occurs. |
| 6 | WDI | Three-level watchdog input; toggling required every 100ms or 1.6s; floating disables watchdog. |
| 7 | PFI | Noninverting input to 1.3V comparator; monitors external voltage divider for power-fail or low-battery warning. |
| 8 | OSC SEL | Oscillator select; high/floating enables internal oscillator; low enables external clock or capacitor timing on OSC IN. |
| 9 | OSC IN | Timing input; accepts external clock (0–250kHz) or 47pF capacitor to adjust watchdog/reset timing per Table 1. |
| 10 | PFO | Active-low power-fail output; goes low when PFI < 1.3V; used for NMI or system shutdown sequencing. |
| 11 | CE IN | Chip-enable gating input; drives CE OUT directly when VCC is valid; connect to GND or VOUT if unused. |
| 12 | CE OUT | Gated chip-enable output; follows CE IN only while VCC > 4.65V; forced high during brownout to block RAM writes. |
| 13 | BATT ON | Active-high battery-on indicator; sinks 25mA; drives base of external PNP transistor to boost VOUT current beyond 50mA. |
| 14 | WDO | Watchdog output; goes low on timeout and remains low until next WDI transition; provides independent fault signaling. |
| 15 | LOW LINE | Active-low VCC-fall indicator; goes low immediately when VCC drops below 4.65V; returns high as soon as VCC recovers. |
| 16 | RESET | Active-high reset output; inverted complement of pin 5; useful for systems requiring active-high reset assertion. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated CE Gating Logic | Prevents µP from writing to CMOS RAM during power-up/down by forcing CE OUT high when VCC < 4.65V, eliminating need for external logic. |
| Selectably Timed Watchdog | Supports both 100ms (fast recovery) and 1.6s (robust software margin) timeout modes via OSC SEL/OSC IN configuration - no external components needed. |
| VOUT Battery Switchover with Hysteresis | 20mV hysteresis prevents oscillation during slow VCC decay; 70mV rise/50mV fall thresholds ensure clean, glitch-free switchover between VCC and VBATT. |
| Low-Power Backup Mode | 1µA max quiescent current with VCC = 0V enables multi-year coin-cell operation for real-time clocks and SRAM retention. |
| Dual Reset Outputs | Provides both active-low (pin 5) and active-high (pin 16) RESET signals, simplifying interface to diverse µP families without level-shifting. |
Applications
| Industrial Controller Power Management | Automotive Body Control Module |
|---|---|
|
Use Scenario: PLC or motion controller maintaining volatile configuration and runtime state during line sags or battery transitions. IC Role / Device Role / Timing Role: Supervisory IC providing 200ms power-up reset hold, 1.3V PFI-based pre-fail interrupt, and VOUT switchover to preserve RAM contents. Use Value: Prevents firmware corruption and parameter loss during 10–100ms brownouts common in factory floor power distribution. |
Use Scenario: BCM retaining door lock status, mirror position, and lighting profiles during engine cranking or alternator dropout. IC Role / Device Role / Timing Role: Dual-role supervisor: generates reset for µP restart and gates CE to EEPROM during <4.65V events. Use Value: Eliminates need for discrete reset IC + external logic gate, reducing BOM count and PCB area in space-constrained modules. |
| Medical Diagnostic Instrument | Smart Energy Meter |
|
Use Scenario: Portable ultrasound or ECG device preserving calibration data and patient session buffers during AC adapter disconnect. IC Role / Device Role / Timing Role: Provides battery-backed VOUT (up to 4.25V), 1µA standby draw, and PFO-triggered data save before full shutdown. Use Value: Enables >5-year coin-cell life while guaranteeing safe shutdown and nonvolatile memory integrity per IEC 62304. |
Use Scenario: Revenue-grade meter logging kWh and tariff data during grid instability or tamper-induced power interruption. IC Role / Device Role / Timing Role: Delivers 200ms reset pulse, CE OUT write protection, and PFI monitoring of DC bus pre-regulator for early fail detection. Use Value: Meets ANSI C12.1 and IEC 62053-21 requirements for data retention and fault logging during 200ms–2s interruptions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX691CSA+ | 8-pin SOIC-N package; lacks CE IN/CE OUT, BATT ON, WDO, LOW LINE, OSC IN/SEL; fixed 50ms reset timeout. | Suitable only for basic reset + battery switchover; cannot support RAM write protection or adjustable timing. | Choose MAX691CSA+ only if board space is constrained and CE gating/watchdog flexibility is unnecessary. |
| MAX695CPE+ | 16-pin PDIP; identical electrical specs and pinout to MAX691CWE but through-hole; same E-temp grade and 4.65V threshold. | Used where manual assembly, prototyping, or legacy through-hole manufacturing is required. | Select MAX695CPE+ for hand-soldered prototypes or industrial control panels where SOIC-W reflow is impractical. |
Compared with MAX691CWE, MAX691CSA+ sacrifices CE gating, watchdog adjustability, and dual reset outputs for smaller footprint, while MAX695CPE+ offers identical functionality in through-hole form - making MAX691CWE optimal for automated SMT production of compact, feature-complete supervisory designs.
Availability
MAX691CWE is available at Aetrix Electronics and suitable for industrial controllers, automotive body electronics, medical diagnostic instruments, and smart energy meters requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for MAX691CWE 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 computing applications.
The MAX690–MAX695 family was designed specifically to consolidate µP power supervision functions - reset, battery switchover, watchdog, power-fail warning, and RAM write protection - into a single IC for space- and reliability-critical embedded systems.
FAQ
What is the reset timeout delay of the MAX691CWE?
The MAX691CWE has a nominal reset timeout delay of 200ms after VCC rises above the 4.65V threshold. This extended delay ensures sufficient time for crystal oscillator stabilization and µP initialization before releasing the reset signal. The value is fixed for the MAX691CWE and differs from the 50ms delay found in the 8-pin MAX690 series. This timing is confirmed in the Electrical Characteristics table and Figure 6 of the MAX690–MAX695 datasheet.
Does the MAX691CWE support adjustable watchdog timeout periods?
Yes, the MAX691CWE supports two selectable watchdog timeout periods: 100ms and 1.6s. Selection is controlled by the logic state of the OSC SEL pin and the signal applied to OSC IN. When OSC SEL is floating and OSC IN is low, the 100ms timeout is active; when both are floating, the 1.6s timeout is used. This configurability is documented in Table 1 and Figure 8 of the MAX690–MAX695 datasheet.
What is the function of the CE IN and CE OUT pins on the MAX691CWE?
The CE IN and CE OUT pins implement chip-enable gating for CMOS RAM or EEPROM. CE OUT is a buffered replica of CE IN when VCC is valid (>4.65V), but is forced high when VCC drops below the reset threshold - preventing µP write operations during brownouts. This hardware-level write protection eliminates software race conditions and is a defining feature distinguishing the 16-pin MAX691CWE from the 8-pin variants.
Can the MAX691CWE operate with a 3.3V main supply?
No, the MAX691CWE is specified for VCC operation from 4.75V to 5.5V and features a 4.65V reset threshold. It is not compatible with 3.3V systems. For 3.3V supervision, designers should consider the MAX636x or MAX6326 families, which offer matching functionality with 3.08V or 3.3V thresholds. Using MAX691CWE with 3.3V would result in permanent reset assertion and failure to operate.
What is the maximum battery voltage supported by the MAX691CWE on the VBATT pin?
The MAX691CWE supports a VBATT input range of 2.0V to 4.25V, as specified in the Electrical Characteristics table. This accommodates standard lithium coin cells (3.0V), alkaline batteries (up to ~3.2V), and rechargeable Li-ion/Li-poly cells in partial charge states. Exceeding 4.25V risks damage, and operation below 2.0V may cause unreliable VOUT switching or PFI comparator inaccuracies.
MAX691CWE 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:
- 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:
- 35ms Minimum
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
MAX691CWE FAQ
1.How can I place an order for MAX691CWE through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX691CWE 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 reliable?
The price and inventory of MAX691CWE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX691CWE is usually 5 days.
3.What payment methods are accepted for MAX691CWE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX691CWE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX691CWE?
MAX691CWE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX691CWE 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?
For technical support, including MAX691CWE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX691CWE requirements.
6.How does Aetrix verify that MAX691CWE is sourced from the original manufacturer or authorized distributors?
All MAX691CWE 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 meets industry standards.
7.What is the process for return or replacement of MAX691CWE?
All MAX691CWE units undergo pre-shipment inspection (PSI). If there is an issue with MAX691CWE, 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 part is unused and in its original packaging.
Return procedure for MAX691CWE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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