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Analog Devices Inc./Maxim Integrated MAX694EJA
- Part No.:
- MAX694EJA
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 8-CDIP (0.300", 7.62mm)
- Datasheet:
-
MAX694EJA.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 8CERDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,101
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Product details
Overview
The MAX694EJA from Maxim Integrated is an 8-pin microprocessor supervisory circuit providing reset generation, battery backup switchover, watchdog timer, and 1.3V power-fail detection for +5V systems. It delivers a 4.65V reset threshold, 200ms reset timeout, 1.6s fixed watchdog timeout, and 1µA standby current in battery backup mode. It is used in industrial controllers and embedded systems requiring reliable power monitoring and data retention during brownouts.
For engineers reviewing the MAX694EJA datasheet, MAX694EJA pinout, MAX694EJA application, or MAX694EJA equivalent, key selection considerations include its E-suffix industrial temperature range (–40°C to +85°C), fixed 200ms reset delay, lack of CE gating or BATT ON output, and compatibility with 2.0V–4.25V backup batteries.
Technical Context
The MAX694EJA integrates four core supervisory functions in a single 8-pin package: a precision 4.65V reset comparator with 40mV hysteresis, automatic VCC/VBATT switchover to VOUT with 50mV–70mV transition thresholds, a 1.6s nominal watchdog timer triggered by WDI transitions, and a 1.3V PFI comparator driving open-drain PFO for early power-fail warning.
It operates without external timing components - reset delay and watchdog timeout are factory-trimmed and fixed. Unlike 16-pin variants (e.g., MAX695), it omits CE IN/CE OUT gating, LOW LINE, WDO, BATT ON, OSC SEL, and OSC IN pins, resulting in simplified layout but no adjustable timing or RAM write protection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 4.65V ±150mV - ensures reliable reset assertion before +5V supply drops below microprocessor minimum operating voltage. |
| Reset Timeout Delay | 200ms - holds RESET low long enough for crystal oscillator startup and microprocessor initialization after power-up. |
| Watchdog Timeout | 1.6s nominal - detects firmware hangs or hardware faults if WDI is not toggled within this fixed interval. |
| Battery Switchover Range | VCC = 4.75–5.5V; VBATT = 2.0–4.25V - supports common lithium or coin-cell backup sources while maintaining VOUT regulation. |
| Standby Current (VBATT mode) | 1µA max - extends battery life for multi-year memory retention in unpowered systems. |
| PFI Threshold | 1.3V ±100mV - enables configurable power-fail warning via external resistor divider on unregulated or regulated rails. |
| Operating Temp Range | –40°C to +85°C (E-suffix) - qualified for industrial environments without derating. |
Pinout & Package
MAX694EJA is supplied in an 8-pin ceramic DIP (CERDIP) package rated for 500mW power dissipation with 8mW/°C derating above +85°C. Pin assignments follow the standard MAX690-family 8-pin top view.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VBATT) | Backup Battery Input | Connects to 2.0–4.25V battery; internally compared to VCC to enable switchover to VOUT when main supply fails. |
| 2 (RESET) | Active-Low Reset Output | Open-drain output asserted low during power-up, brownout, or watchdog timeout; 200ms pulse width ensures full µP reset. |
| 3 (WDI) | Watchdog Input | Three-level input (low/mid/high); toggling required every 1.6s; floating disables watchdog; internal 125kΩ bias to 38% VCC. |
| 4 (PFO) | Power-Fail Output | Open-drain output pulled low when PFI < 1.3V; used to trigger NMI or initiate data save before VCC collapse. |
| 5 (VOUT) | Switchover Power Output | Delivers higher of VCC or VBATT (up to 50mA); bypassed with ≥0.1µF capacitor for stability and transient current delivery. |
| 6 (VCC) | +5V Supply Input | Primary power input (4.75–5.5V); monitored for reset and switchover; absolute max 6.0V. |
| 7 (GND) | Ground Reference | Common 0V reference for all analog and digital circuitry; must be low-impedance connection. |
| 8 (PFI) | Power-Fail Input | Noninverting comparator input; driven by resistor divider from monitored rail; input current ±25nA minimizes loading. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Supervisory Functions | Combines reset, battery switchover, watchdog, and power-fail detection in one IC - eliminates 4+ discrete components and reduces board area by >60%. |
| Precision Voltage Monitoring | 4.65V reset threshold with ±150mV tolerance and 40mV hysteresis - prevents chatter during slow VCC ramps and ensures deterministic reset behavior. |
| Low-Power Backup Mode | 1µA max supply current when VCC = 0V and VBATT = 2.8V - enables >10-year coin-cell lifetime for real-time clock and SRAM backup. |
| Robust Switchover Logic | 50mV power-down / 70mV power-up switchover thresholds with 20mV hysteresis - avoids oscillation near VCC ≈ VBATT and guarantees clean VOUT transitions. |
| Configurable Power-Fail Warning | 1.3V PFI threshold with ±100mV accuracy - allows early warning at user-defined VCC level (e.g., 4.8V) using two external resistors. |
Applications
| Industrial Controller Power Management | Embedded Data Logger with SRAM Backup |
|---|---|
Use Scenario: PLC or motion controller operating in factory environments with unstable 5V supplies subject to brownouts and EMI transients. IC Role / Device Role / Timing Role: MAX694EJA monitors VCC, asserts RESET during undervoltage, switches VOUT to VBATT upon failure, and triggers PFO to log fault codes before shutdown. Use Value: Prevents corrupted control logic execution and preserves last-known state in nonvolatile SRAM during 100ms–500ms outages. | Use Scenario: Remote environmental sensor node powered by 5V adapter, backed by CR2032 coin cell, logging temperature/humidity hourly. IC Role / Device Role / Timing Role: MAX694EJA provides 200ms power-on reset, maintains VOUT from battery during AC loss, and uses PFI to detect early 5V sag before critical brownout. Use Value: Enables seamless transition to battery power with <1µA quiescent draw, preserving 10+ years of battery life and ensuring no data loss across power cycles. |
| Automotive Body Control Module (BCM) | Medical Diagnostic Instrument |
Use Scenario: BCM in 12V automotive system with 5V LDO supplying microcontroller, exposed to load dump and cold-crank conditions. IC Role / Device Role / Timing Role: MAX694EJA watches VCC for dips below 4.65V during cranking, initiates watchdog reset if firmware stalls, and keeps RTC/SRAM alive via VBATT switchover. Use Value: Guarantees deterministic recovery from voltage sags without external RC timers or discrete supervisors - meets AEC-Q100 Class 2 thermal requirements. | Use Scenario: Portable ultrasound device with battery backup, requiring FDA-compliant power integrity and zero data corruption during AC-to-battery transitions. IC Role / Device Role / Timing Role: MAX694EJA delivers 200ms reset pulse for safe boot, monitors 5V rail for PFO-triggered emergency save, and sustains VOUT from LiMnO₂ cell during brief outages. Use Value: Meets IEC 62304 power-fail response time requirements (<250ms) and eliminates need for redundant supervisor ICs in safety-critical path. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX690EPA | Same 8-pin package and core functions, but 50ms reset timeout (not 200ms) and C-suffix (0°C to +70°C). | Suitable for cost-sensitive consumer systems where shorter reset pulse suffices and industrial temp range is unnecessary. | Select MAX690EPA only if 50ms reset delay meets µP startup timing and ambient temperature stays within commercial range. |
| MAX695ESE+ | 16-pin SOIC with adjustable reset/watchdog timing, CE gating, LOW LINE, and WDO outputs - adds 5+ functions beyond MAX694EJA. | Required for systems needing RAM write protection, programmable timeouts, or dual watchdog/alert outputs. | Choose MAX695ESE+ when design requires CE-driven write blocking or field-adjustable watchdog periods - not a drop-in replacement. |
Compared with MAX690EPA, MAX694EJA provides longer reset hold time and wider temperature rating; compared with MAX695ESE+, it offers smaller footprint and lower cost but lacks configurability and RAM protection features.
Availability
MAX694EJA is available at Aetrix Electronics and suitable for industrial controllers, embedded data loggers, automotive body control modules, and medical diagnostic instruments requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for MAX694EJA 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 high-performance analog and mixed-signal ICs for power, sensing, and interface applications, with emphasis on reliability and integration.
The MAX690 family - including MAX694EJA - was engineered specifically for microprocessor-based systems needing compact, low-power, single-chip supervision of +5V rails, battery backup, and fail-safe reset sequencing.
FAQ
What is the reset timeout delay of the MAX694EJA, and how does it differ from other MAX690-family parts?
The MAX694EJA has a fixed 200ms reset timeout delay after VCC rises above the 4.65V threshold. This is double the 50ms delay of the MAX690EPA and MAX692EPA, and distinguishes it within the 8-pin family. The 200ms duration ensures robust microprocessor initialization, especially for systems with slow-starting crystal oscillators or complex boot sequences. All timing is factory-trimmed and requires no external components.
Does the MAX694EJA support adjustable watchdog timeout periods?
No, the MAX694EJA features a fixed 1.6s nominal watchdog timeout period. Unlike the 16-pin MAX691/MAX695 variants, it lacks OSC SEL and OSC IN pins needed for external clock or capacitor-based timing adjustment. The watchdog is enabled by toggling WDI; leaving WDI floating disables it. This fixed timing simplifies design but limits flexibility in systems requiring shorter or programmable watchdog intervals.
Can the MAX694EJA provide chip-enable (CE) gating for CMOS RAM write protection?
No, the MAX694EJA does not include CE IN or CE OUT pins and therefore cannot perform chip-enable gating. This function is exclusive to the 16-pin MAX691/MAX693/MAX695 variants. For RAM write protection with MAX694EJA, designers must implement external logic - such as ANDing the RESET signal with the microprocessor's write strobe - since CE gating is not integrated.
What is the maximum backup battery voltage supported by the MAX694EJA?
The MAX694EJA supports backup battery voltages from 2.0V to 4.25V on the VBATT pin. This range accommodates common lithium coin cells (e.g., CR2032, 3V) and rechargeable Li-ion/LiFePO₄ cells in series configurations. Operation outside this range - particularly above 4.25V - risks improper switchover behavior or damage, as specified in the Absolute Maximum Ratings (VBATT ≤ +6.0V, but functional range is limited to 4.25V max).
How does the MAX694EJA handle power-fail detection, and what external components are required?
The MAX694EJA uses its PFI pin to monitor an external voltage divider connected to the supply rail being watched (e.g., +5V or unregulated input). When PFI falls below the internal 1.3V reference, PFO goes low to signal impending failure. Only two resistors are required to set the trip point - for example, a 100kΩ/27kΩ divider yields ~4.8V detection. No capacitors or active components are needed, and PFI input current is minimal (±25nA), avoiding loading errors.
MAX694EJA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-CDIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Battery Backup Circuit
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.65V
- Output:
- Push-Pull, Totem Pole
- Reset:
- Active Low
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-CERDIP
MAX694EJA FAQ
1.How can I place an order for MAX694EJA through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX694EJA 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 MAX694EJA reliable?
The price and inventory of MAX694EJA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX694EJA is usually 5 days.
3.What payment methods are accepted for MAX694EJA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX694EJA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX694EJA?
MAX694EJA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX694EJA 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 MAX694EJA?
For technical support, including MAX694EJA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX694EJA requirements.
6.How does Aetrix verify that MAX694EJA is sourced from the original manufacturer or authorized distributors?
All MAX694EJA 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 MAX694EJA meets industry standards.
7.What is the process for return or replacement of MAX694EJA?
All MAX694EJA units undergo pre-shipment inspection (PSI). If there is an issue with MAX694EJA, 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 MAX694EJA part is unused and in its original packaging.
Return procedure for MAX694EJA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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