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Analog Devices Inc./Maxim Integrated MAX690SCSA-T
- Part No.:
- MAX690SCSA-T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX690SCSA-T.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,769
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Product details
Overview
MAX690SCSA-T from Maxim Integrated is a 3.3V microprocessor supervisory circuit with active-low RESET output, 2.925V reset threshold, 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover. It monitors VCC for brownout detection, asserts reset during power-up/down, and switches VOUT to VBATT when VCC falls below 2.40V - used in embedded controllers requiring reliable power-fail warning and RAM backup.
For engineers reviewing the MAX690SCSA-T datasheet, MAX690SCSA-T pinout, MAX690SCSA-T application, or MAX690SCSA-T equivalent, key selection criteria include reset threshold tolerance (±4%), PFI comparator accuracy (±75mV), VCC supply current (40µA typ), battery leakage (0.4–1µA), and SO-8 package compatibility with industrial temperature range (–40°C to +85°C).
Technical Context
The MAX690SCSA-T integrates a precision reset comparator with 10mV hysteresis, a non-disableable 1.6s watchdog timer cleared by WDI edges, and a dual-path battery switchover circuit using PMOS switches (3Ω VCC-to-VOUT, 140Ω VBATT-to-VOUT). Its PFI input accepts external voltage dividers for multi-rail monitoring, while RESET remains asserted until VCC exceeds VRST and the 200ms timer expires.
It operates across VCC = 3.02V to 5.5V and VBATT = –0.3V to +6.0V, supports manual reset via MR (70µA internal pull-up), guarantees RESET assertion down to VCC = 1V, and disables PFI/PFO functionality when VCC < VSW (2.40V) during battery-backup mode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 2.925V (nominal), ±4% tolerance - ensures reset triggers before VCC drops below 2.85V in 3.3V ±10% systems |
| Reset Timeout Period | 200ms (typ), 140–280ms over temp - provides sufficient hold time for µP initialization after power recovery |
| VCC Supply Current | 40µA (typ, VCC < 3.6V) - enables ultra-low-power operation in battery-backed portable equipment |
| Battery Supply Current | 0.4–1µA (max, –40°C to +85°C) - minimizes drain on lithium backup cells during extended standby |
| Watchdog Timeout | 1.6s (typ), 1.12–2.24s over temp - detects µP lockup without requiring software intervention |
| Power-Fail Threshold Accuracy | ±75mV - supports accurate undervoltage detection of auxiliary rails via PFI divider networks |
| Operating Temperature | –40°C to +85°C - qualified for industrial embedded controller environments |
Pinout & Package
MAX690SCSA-T is housed in an 8-pin SOIC (SO-8) package with standard 1.27mm pitch, RoHS-compliant lead-free finish (+ suffix implied per ordering guide), and thermal performance rated at 471mW continuous dissipation at +70°C (derating 5.88mW/°C above).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - VOUT | CMOS RAM supply output | Switches between VCC (via 3Ω PMOS) and VBATT (via 140Ω PMOS) based on VCC/VBATT comparison; connects to static RAM VDD |
| 2 - VCC | Main system supply input | Primary 3.0V/3.3V power rail monitored for reset assertion; supports 3.02V–5.5V operating range |
| 3 - GND | Ground reference | Common return for all internal circuits and external decoupling capacitors (0.1µF recommended) |
| 4 - PFI | Power-fail input | Accepts divided voltage from auxiliary rail; trips PFO low when input falls below 1.237V ±75mV |
| 5 - PFO | Power-fail open-drain output | Active-low signal indicating VCC drop below VSW or PFI < VPFT; can drive MR on MAX704/MAX806 |
| 6 - WDI | Watchdog input | Edge-sensitive (rising/falling) trigger; resets internal 1.6s timer; cannot be disabled |
| 7 - RESET | Active-low reset output | Push-pull output asserted low during power-up, brownout, or watchdog timeout; guaranteed valid down to VCC = 1V |
| 8 - VBATT | Backup battery input | Supports VBATT > VCC (e.g., 3.6V Li cell); enables seamless switchover without external diodes |
Key Features
| Feature | Design Value |
|---|---|
| Precision reset comparator | 2.925V threshold with ±4% tolerance and 10mV hysteresis - prevents chatter during slow VCC ramps |
| Guaranteed RESET assertion to VCC = 1V | Ensures deterministic µP reset even during deep brownout conditions where other supervisors fail |
| Battery switchover with VCC > VBATT support | Enables use of 3.6V lithium cells without level-shifting; switchover occurs at 2.40V to preserve RAM data margin |
| 200ms reset timeout with restart-on-brownout | Timer reinitializes each time VCC dips below VRST - eliminates race conditions in noisy power environments |
| Low-quiescent-current design | 40µA VCC supply current and sub-1µA battery leakage extend shelf life in always-on portable instruments |
Applications
| Battery-Powered Embedded Controller | Critical µP Power Monitoring |
|---|---|
Use Scenario: Industrial PLC module powered by 3.3V main rail and 3.6V lithium coin cell, requiring RAM retention during AC loss. IC Role / Device Role / Timing Role: Supervisory IC providing VCC brownout detection, automatic VBATT switchover, and 200ms RESET hold for µP safe shutdown. Use Value: Prevents RAM corruption by asserting RESET before VCC drops below 2.85V and switching VOUT to VBATT at 2.40V - preserving data integrity across 100+ hour outages. |
Use Scenario: Medical diagnostic device with ARM Cortex-M4 µP that must never execute invalid code due to unstable supply. IC Role / Device Role / Timing Role: Primary power supervisor generating active-low RESET synchronized to VCC ramp, with watchdog fallback for firmware hangs. Use Value: Guarantees RESET assertion down to VCC = 1V and restarts 200ms timer on every brownout dip - eliminating false starts and undefined behavior. |
| Intelligent Instrumentation | Portable Test Equipment |
Use Scenario: Handheld multimeter with EEPROM configuration storage and real-time clock, operating from rechargeable Li-ion. IC Role / Device Role / Timing Role: Dual-function supervisor monitoring main 3.3V rail and generating PFO interrupt for low-battery warning via PFI divider. Use Value: Uses ±75mV PFI threshold accuracy to detect auxiliary rail faults within 50mV, enabling precise battery SOC estimation before shutdown. |
Use Scenario: Battery-operated oscilloscope front-end with FPGA configuration SRAM needing persistent backup during hot-swap battery changes. IC Role / Device Role / Timing Role: Switchover controller isolating VCC transients during battery insertion/removal while maintaining VOUT stability. Use Value: Allows safe VBATT replacement with VCC valid (VCC > VSW) and 0.1µF local decoupling - no RESET glitch or RAM loss observed. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX704SCSA-T | Same 2.925V reset threshold, but adds active-high RESET (open-drain) and removes PFO output | Lacks power-fail warning capability; suited for designs needing only reset + watchdog + battery switchover | Select MAX704SCSA-T if PFI/PFO functionality is unused and board space allows open-drain pull-up |
| MAX802SCSA-T | Tighter reset threshold tolerance (±2% vs. ±4%) and improved PFI accuracy (±2% vs. ±75mV) | Better suited for high-precision 3.3V systems with tight supply margins; same pinout and function set | Choose MAX802SCSA-T when reset timing margin is critical and cost premium is acceptable for enhanced accuracy |
Compared with MAX704SCSA-T and MAX802SCSA-T, the MAX690SCSA-T uniquely retains both active-low RESET and PFO outputs in SO-8, enabling simultaneous reset assertion and power-fail interrupt generation - essential for systems requiring dual fault signaling without additional logic.
Availability
MAX690SCSA-T is available at Aetrix Electronics and suitable for battery-powered computers and controllers, intelligent instrumentation, and critical µP power monitoring requiring stable component supply across industrial temperature ranges and long-term lifecycle support.
Supply support for MAX690SCSA-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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, computing, and communications applications.
The MAX690 family was designed specifically for 3.0V/3.3V microprocessor systems needing integrated reset supervision, watchdog protection, and seamless battery-backup switchover - targeting reliability-critical embedded controllers and portable instrumentation.
FAQ
What is the exact reset threshold voltage for MAX690SCSA-T?
The MAX690SCSA-T has a nominal reset threshold voltage of 2.925V, with a specified tolerance of ±4% over temperature and supply variations. This means reset is guaranteed to assert before VCC falls below 2.85V and will not trigger prematurely as long as VCC remains above 3.00V under normal operating conditions - matching 3.3V ±10% system requirements.
Does MAX690SCSA-T support battery voltage higher than VCC?
Yes, the MAX690SCSA-T explicitly supports VBATT exceeding VCC - such as a 3.6V lithium coin cell with a 3.3V main supply. Its internal battery switchover circuit activates when VCC falls below 2.40V (VSW), connecting VBATT to VOUT through a 140Ω switch, and ensures no reverse current flows into VCC during backup mode.
Can the watchdog timer in MAX690SCSA-T be disabled?
No, the watchdog timer in MAX690SCSA-T cannot be disabled. It is a fixed-function 1.6s timeout circuit that clears only on WDI edge transitions (rising or falling) or during RESET assertion. If continuous watchdog supervision is not required, consider the MAX706SCSA-T or MAX708SCSA-T as alternatives without watchdog functionality.
What is the maximum allowable VCC transient duration that will not trigger reset in MAX690SCSA-T?
According to the MAX690SCSA-T datasheet, a negative-going VCC transient 100mV below the reset threshold (i.e., ~2.825V) can last up to 40µs without causing an unintended reset pulse. Immunity decreases with larger overdrive; for example, a 200mV overdrive limits allowable duration to ~15µs. A 0.1µF bypass capacitor at VCC improves noise rejection.
How does MAX690SCSA-T behave when no backup battery is connected?
When no backup battery is used, MAX690SCSA-T requires VBATT and VOUT to be tied directly to VCC to maintain proper operation. Leaving VBATT floating or unconnected may cause undefined behavior or damage. In battery-less designs, the MAX706SCSA-T or MAX708SCSA-T - which lack battery switchover - are more appropriate alternatives.
MAX690SCSA-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Battery Backup Circuit
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 2.925V
- Output:
- Push-Pull, Totem Pole
- Reset:
- Active Low
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX690SCSA-T FAQ
1.How can I place an order for MAX690SCSA-T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX690SCSA-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 MAX690SCSA-T reliable?
The price and inventory of MAX690SCSA-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX690SCSA-T is usually 5 days.
3.What payment methods are accepted for MAX690SCSA-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX690SCSA-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX690SCSA-T?
MAX690SCSA-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX690SCSA-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 MAX690SCSA-T?
For technical support, including MAX690SCSA-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX690SCSA-T requirements.
6.How does Aetrix verify that MAX690SCSA-T is sourced from the original manufacturer or authorized distributors?
All MAX690SCSA-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 MAX690SCSA-T meets industry standards.
7.What is the process for return or replacement of MAX690SCSA-T?
All MAX690SCSA-T units undergo pre-shipment inspection (PSI). If there is an issue with MAX690SCSA-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 MAX690SCSA-T part is unused and in its original packaging.
Return procedure for MAX690SCSA-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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