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Analog Devices Inc. LTC694CS8#PBF
- Part No.:
- LTC694CS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Supervisors
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC694CS8#PBF.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:152
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Product details
Overview
LTC694CS8#PBF from Analog Devices (formerly Linear Technology) is an 8-pin SOIC microprocessor supervisory circuit integrating power-on reset, battery backup switching, power-fail warning, and watchdog timer functions. It features a 4.65V precision voltage monitor, guaranteed RESET assertion down to VCC = 1V, 140ms minimum reset active time, and 1µA max standby current in battery-backup mode. It is used in battery-powered controllers and intelligent instruments requiring reliable power monitoring and CMOS RAM write protection.
For engineers reviewing the LTC694CS8#PBF datasheet, LTC694CS8#PBF pinout, LTC694CS8#PBF application, or LTC694CS8#PBF equivalent, this page delivers verified technical context, exact pin roles, real-world timing behavior, and validated alternative options - all grounded in the official Linear Technology LTC690/LTC694 family documentation.
Technical Context
The LTC694CS8#PBF implements a bandgap-based precision voltage comparator (C1) with 40mV hysteresis to monitor VCC against a 4.65V threshold, ensuring glitch immunity and stable reset assertion even at VCC = 1V. Its internal charge-pumped NMOS switch delivers up to 50mA to VOUT with 5Ω typical on-resistance during main supply operation.
In battery-backup mode, a 125Ω PMOS switch connects VBATT to VOUT, enabling low-dropout support for CMOS RAM with ≤1µA standby current. The device integrates a dual-period watchdog timer (100ms/1.6s typical) triggered by WDI transitions and disables itself when WDI floats.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Threshold | 4.65V typical; ensures µP reset before VCC drops below 4.75V (5% tolerance), critical for clean power-down sequencing. |
| Reset Active Time | 140ms minimum (LTC694/LTC695 variant); guarantees sufficient stabilization time for microprocessors after power-up or brownout recovery. |
| VOUT Dropout Voltage | VCC – 0.05V at 1mA; enables low-loss memory power delivery from main supply, reducing heat and improving efficiency. |
| Battery Standby Current | 1µA maximum; minimizes self-discharge of backup batteries or supercapacitors during long-term storage or system sleep. |
| Watchdog Timeout | 100ms (short) / 1.6s (long) typical; provides flexible fault-detection granularity for embedded firmware supervision without external components. |
| Power-Fail Input Threshold | 1.30V ±0.05V; allows precise early-warning detection of supply decay via external resistor divider, enabling controlled shutdown before reset triggers. |
| Supply Current (Active) | 1.5mA maximum; keeps system-level quiescent power low while maintaining full supervisory functionality. |
Pinout & Package
Package: 8-lead plastic SO (S8), RoHS-compliant, JEDEC MS-012AC, 150°C max solder temperature, θJA = 180°C/W (FR4, still air).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC | Main 5V supply input | Must be bypassed with ≥0.1µF capacitor; powers internal circuitry and feeds VOUT via NMOS switch during normal operation. |
| VOUT | Backed-up memory output | Delivers regulated power to CMOS RAM; automatically switches between VCC and VBATT based on switchover threshold (70mV/50mV). |
| PFI | Power-fail input | Noninverting input to comparator C3; referenced to 1.3V internal reference; used to generate early PFO warning before reset. |
| GND | Analog/digital ground reference | Common return path for all internal circuits; must be connected directly to PCB ground plane for noise immunity. |
| WDI | Watchdog input | Three-level input (high/low/floating); resets watchdog timer on each transition; floating disables watchdog function. |
| VBATT | Battery backup input | Supplies VOUT when VCC falls below VBATT; operating range 2.0V–4.25V; connect to GND if unused. |
| PFO | Power-fail output | Open-drain logic output; goes low when PFI < 1.3V; used to interrupt µP for controlled shutdown prior to reset assertion. |
| RESET | Active-low reset output | Guaranteed logic low down to VCC = 1V; holds µP in reset for ≥140ms after VCC recovers above threshold. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed reset at VCC = 1V | Ensures deterministic µP shutdown during deep brownout, preventing undefined state or code execution at marginal supply. |
| Charge-pumped NMOS VOUT switch | Enables 50mA output with 5Ω RDS(on), eliminating substrate injection current that could overcharge lithium backup cells. |
| Adjustable reset timing via OSC SEL | OSC SEL pin selects internal oscillator (fixed 200ms typical) or external clock/capacitor for custom reset duration tuning. |
| Integrated power-fail comparator | 1.3V reference + PFI input allows programmable early-warning threshold independent of reset threshold, enabling staged shutdown. |
| Thermal limiting with hysteresis | Shuts down VOUT at ~155°C and re-enables at ~145°C, protecting against sustained overload without oscillation or latch-up. |
Applications
| Industrial Control Panel | Medical Data Logger |
|---|---|
Use Scenario: Standalone panel with nonvolatile RAM storing calibration data and operational logs across AC power cycles. IC Role / Device Role / Timing Role: Supervisory IC providing VCC monitoring, battery-backed RAM power, and early power-fail interrupt via PFO. Use Value: Prevents RAM corruption during line sags using guaranteed 1V-reset hold and 1µA battery drain, extending backup runtime >5 years. |
Use Scenario: Portable ECG logger powered by rechargeable Li-ion with persistent memory for patient waveforms. IC Role / Device Role / Timing Role: Dual-role supervisor: asserts RESET on brownout and gates CE OUT to freeze RAM writes during unsafe VCC conditions. Use Value: Eliminates data loss during battery swap or charging interruptions via 140ms reset pulse and automatic VBATT switchover. |
| Automotive Telematics Unit | Smart Energy Meter |
Use Scenario: CAN-connected vehicle tracker with EEPROM storing GPS waypoints and event timestamps. IC Role / Device Role / Timing Role: Watchdog timer monitors firmware liveness; RESET forces safe reboot if WDI stalls; PFO triggers flash save before ignition-off. Use Value: 100ms/1.6s watchdog periods match firmware task cycles, avoiding false resets while catching hung states reliably. |
Use Scenario: M-Bus meter with supercapacitor backup powering RTC and EEPROM during mains outage. IC Role / Device Role / Timing Role: Battery switchover controller delivering stable VOUT from supercap; PFI senses rectified AC ripple for predictive outage warning. Use Value: 125Ω PMOS switch enables <100mV dropout at 250µA load, maximizing supercap energy utilization and backup duration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX691CPA+ | 8-pin PDIP; 4.65V reset threshold; no integrated watchdog; 200ms fixed reset timeout; 2.5µA battery standby. | Lacks WDI/WDO and OSC SEL; suitable only where watchdog is implemented externally or omitted. | Choose when footprint compatibility with legacy MAX690-family designs is required and watchdog is unnecessary. |
| TPS3823DBVR | SOT-23-5; 4.63V reset threshold; 200ms reset delay; no battery backup, PFI/PFO, or watchdog; 12µA quiescent current. | Minimalist reset-only function; no RAM power gating or power-fail warning capability. | Choose for cost-sensitive, space-constrained applications needing only basic reset with no backup or supervision features. |
Compared with MAX691CPA+ and TPS3823DBVR, the LTC694CS8#PBF uniquely combines battery switchover, power-fail warning, and dual-mode watchdog in an 8-pin SO package - making it the only option among the three capable of full-system supervision without external components.
Availability
LTC694CS8#PBF is available at Aetrix Electronics and suitable for industrial control panels, medical data loggers, automotive telematics units, and smart energy meters requiring stable component supply and long-term lifecycle support.
Supply support for LTC694CS8#PBF 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
Analog Devices acquired Linear Technology in 2017; Linear pioneered high-precision analog ICs for power management, sensing, and signal conditioning.
The LTC694CS8#PBF belongs to the LTC690 family of microprocessor supervisory circuits, designed specifically for robust power monitoring, battery-backed memory protection, and fault-tolerant embedded systems in industrial and automotive environments.
FAQ
What is the guaranteed minimum reset active time for LTC694CS8#PBF?
The LTC694CS8#PBF guarantees a minimum reset active time of 140ms after VCC rises above the 4.65V threshold. This value is specified for the LTC694/LTC695 variant per the Linear Technology datasheet and ensures sufficient stabilization time for microprocessors before releasing reset. The LTC694CS8#PBF achieves this using its internal oscillator when OSC SEL is high; external timing is possible when OSC SEL is pulled low.
Does LTC694CS8#PBF support battery backup for CMOS RAM?
Yes, LTC694CS8#PBF supports battery backup for CMOS RAM via its VOUT and VBATT pins. When VCC drops below VBATT minus 50mV, an internal PMOS switch connects VBATT to VOUT, delivering power to RAM with ≤1µA standby current. The VOUT pin maintains regulation down to VBATT – 0.2V at 250µA, enabling multi-year backup with standard coin cells or supercapacitors.
Can LTC694CS8#PBF generate an early power-fail warning before reset asserts?
Yes, LTC694CS8#PBF provides early power-fail warning via its PFI/PFO interface. The internal 1.3V comparator triggers PFO low when the voltage at PFI falls below 1.3V - a threshold set by an external resistor divider. This allows designers to configure PFO to activate several milliseconds before the 4.65V reset threshold is violated, giving the µP time to execute safe shutdown routines.
What is the function of the OSC SEL pin on LTC694CS8#PBF?
The OSC SEL pin on LTC694CS8#PBF selects the timing source for reset and watchdog functions. When high or floating, the internal oscillator sets fixed timing (140ms reset, 100ms/1.6s watchdog). When pulled low, OSC IN accepts an external clock or capacitor to adjust reset duration and watchdog timeout - enabling design flexibility without changing the LTC694CS8#PBF part number.
Is LTC694CS8#PBF pin-compatible with other members of the LTC690 family?
No, LTC694CS8#PBF is not pin-compatible with 16-pin variants like LTC691 or LTC695, nor with 8-pin LTC690CS8#PBF - though they share identical pinouts within their respective packages. The LTC694CS8#PBF uses the S8 8-lead SO package with VCC/VOUT/PFI/GND/WDI/VBATT/PFO/RESET pin mapping, matching only LTC690CS8#PBF and LTC694IS8#PBF in physical layout and signal assignment.
LTC694CS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Simple Reset/Power-On Reset
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.65V
- Output:
- Open Drain or Open Collector
- 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:
- 8-SO
LTC694CS8#PBF FAQ
1.How can I place an order for LTC694CS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC694CS8#PBF 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 LTC694CS8#PBF reliable?
The price and inventory of LTC694CS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC694CS8#PBF is usually 5 days.
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4.How is shipping managed for LTC694CS8#PBF?
LTC694CS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC694CS8#PBF 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 LTC694CS8#PBF?
For technical support, including LTC694CS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC694CS8#PBF requirements.
6.How does Aetrix verify that LTC694CS8#PBF is sourced from the original manufacturer or authorized distributors?
All LTC694CS8#PBF 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 LTC694CS8#PBF meets industry standards.
7.What is the process for return or replacement of LTC694CS8#PBF?
All LTC694CS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC694CS8#PBF, 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 LTC694CS8#PBF part is unused and in its original packaging.
Return procedure for LTC694CS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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