4-Pin Microprocessor Power Supply Supervisors # CAT811ZTBIT Technical Documentation
Manufacturer : CATALYST
Component Type : Microprocessor Reset Circuit
## 1. Application Scenarios
### Typical Use Cases
The CAT811ZTBIT serves as a voltage supervisor and reset controller in microcontroller-based systems, primarily ensuring proper initialization and operation during power-up, power-down, and brownout conditions. Typical applications include:
- Power-On Reset Sequencing : Monitors system voltage during startup, holding the microcontroller in reset until the supply voltage stabilizes above the threshold voltage (typically 2.93V for Vcc = 3.0V variant)
- Brownout Protection : Continuously monitors supply voltage during operation, generating a reset signal when voltage drops below the specified threshold
- Manual Reset Control : Provides push-button reset functionality through the MR (Manual Reset) pin for system debugging and user-initiated resets
### Industry Applications
- Consumer Electronics : Smart home devices, IoT sensors, and wearable technology where reliable startup and operation are critical
- Industrial Control Systems : PLCs, motor controllers, and automation equipment requiring robust power monitoring
- Automotive Electronics : Infotainment systems, body control modules, and telematics units (non-safety critical applications)
- Medical Devices : Portable monitoring equipment and diagnostic tools where consistent operation is essential
- Embedded Systems : Single-board computers, development boards, and prototyping systems
### Practical Advantages and Limitations
Advantages:
- High Accuracy : ±1.5% threshold accuracy ensures reliable reset generation
- Low Power Consumption : 15μA typical supply current extends battery life in portable applications
- Small Form Factor : SOT-23-3 package (2.8mm × 2.9mm) saves board space
- Wide Operating Range : 1.0V to 5.5V supply voltage compatibility
- Immediate Response : No delay capacitors required for basic operation
Limitations:
- Fixed Threshold : Cannot be adjusted for custom voltage levels (available in fixed threshold variants only)
- Limited Reset Timeout : Fixed 140ms minimum reset pulse width may not suit all applications
- Temperature Sensitivity : Threshold voltage varies with temperature (typical ±50mV over -40°C to +85°C)
- No Watchdog Timer : Lacks additional monitoring features found in more complex supervisors
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Insufficient Bypassing
- Problem : Noise on supply lines causing false reset triggers
- Solution : Place 0.1μF ceramic capacitor within 10mm of Vcc pin, with larger bulk capacitance (10μF) near power entry point
Pitfall 2: Reset Signal Integrity
- Problem : Long trace routing introducing noise or signal degradation
- Solution : Route reset signal as controlled impedance trace, keep length under 50mm when possible
Pitfall 3: Manual Reset Debouncing
- Problem : Mechanical switch bounce causing multiple reset pulses
- Solution : Implement hardware debouncing (RC filter with 1-10ms time constant) on MR pin or handle in software
Pitfall 4: Power Sequencing Conflicts
- Problem : Reset asserted during valid power conditions due to slow-rising supplies
- Solution : Ensure power supply rise time is faster than 1ms/V, or select higher threshold variant
### Compatibility Issues with Other Components
Microcontroller Interfaces:
- Compatible with most CMOS/TTL logic inputs
- Ensure reset output voltage levels match microcontroller requirements
- Check for open-drain vs. push-pull configuration requirements
Power Supply Considerations:
- Works with LDO regulators, switching converters, and battery supplies
- Monitor same supply rail powering the microcontroller core
- Consider
