CMOS Switched-Capacitor Voltage Converters# ADM660AR Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The ADM660AR is a switched-capacitor voltage converter IC primarily used for voltage inversion and voltage doubling applications. Typical implementations include:
- Negative Voltage Generation : Converting +5V to -5V for operational amplifier power supplies
- Voltage Doubling : Generating +10V from +5V input for higher voltage requirements
- Battery-Powered Systems : Creating dual-rail supplies from single battery sources
- Signal Conditioning Circuits : Providing negative rails for analog signal processing
### Industry Applications
Industrial Automation :
- PLC analog I/O modules requiring ±5V or ±10V supplies
- Sensor interface circuits with bipolar operational amplifiers
- Process control instrumentation
Telecommunications :
- Line interface circuits
- Modem power supply sections
- RF amplifier bias networks
Medical Electronics :
- Portable medical monitoring equipment
- Patient monitoring systems
- Diagnostic instrument power supplies
Consumer Electronics :
- Audio equipment requiring dual power rails
- Portable devices with mixed-signal circuits
- LCD display bias generation
### Practical Advantages and Limitations
Advantages :
- High Efficiency : Typically 85-95% conversion efficiency
- Compact Solution : Requires minimal external components (only capacitors)
- Wide Operating Range : 1.5V to 6.0V input voltage range
- Low Quiescent Current : 120μA typical, suitable for battery operation
- No Inductors Required : Eliminates EMI concerns associated with switching regulators
Limitations :
- Limited Output Current : Maximum 50mA output current
- Output Impedance : Higher than linear regulators (typically 50-100Ω)
- Noise Generation : Switching frequency (approx. 25kHz) can introduce noise
- Temperature Sensitivity : Performance degrades at temperature extremes
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pump Capacitor Selection :
- Pitfall : Using capacitors with insufficient voltage rating or high ESR
- Solution : Select 10μF tantalum or ceramic capacitors with voltage rating ≥ 2× input voltage
Output Regulation :
- Pitfall : Poor load regulation under dynamic conditions
- Solution : Add small output capacitor (1-10μF) close to the load
Start-up Issues :
- Pitfall : Inrush current causing supply droop
- Solution : Implement soft-start circuitry or use larger input decoupling
### Compatibility Issues
Digital Circuits :
- The 25kHz switching frequency can interfere with sensitive analog circuits
- Mitigation : Use separate ground planes and proper filtering
Mixed-Signal Systems :
- Switching noise may affect high-resolution ADCs
- Solution : Implement LC filters and physical separation
Microcontroller Interfaces :
- Ensure shutdown pin compatibility with microcontroller logic levels
- Verify timing requirements for enable/disable sequences
### PCB Layout Recommendations
Component Placement :
- Place pump capacitors (C1, C2) as close as possible to the IC pins
- Position output capacitor within 5mm of VOUT pin
- Keep input bypass capacitor adjacent to V+ pin
Routing Guidelines :
- Use short, wide traces for high-current paths (pump capacitor connections)
- Implement separate analog and digital ground planes
- Route sensitive analog signals away from switching nodes
Thermal Management :
- Provide adequate copper area for heat dissipation
- Consider thermal vias for multilayer boards
- Ensure proper airflow in enclosed systems
## 3. Technical Specifications
### Key Parameter Explanations
Input Voltage Range (V+) : 1.5V to 6.0V
- Determines the operating supply range and output voltage capabilities
