How to Use icl7660: Examples, Pinouts, and Specs

The ICL7660 is a versatile voltage converter integrated circuit (IC) designed to generate a negative voltage from a positive voltage supply. It operates using a charge-pump principle, making it an efficient and compact solution for applications requiring a dual power supply. The ICL7660 is widely used in analog circuits, such as operational amplifiers, data acquisition systems, and instrumentation, where a negative voltage rail is essential.

• Powering operational amplifiers in dual-supply configurations
• Generating negative voltage rails for analog circuits
• Battery-powered systems requiring compact voltage conversion
• Portable instrumentation and data acquisition systems

• Input Voltage Range: +1.5V to +10V
• Output Voltage: Approximately -Vin (negative of the input voltage)
• Maximum Output Current: 20mA (typical), 40mA (maximum, with reduced efficiency)
• Quiescent Current: 200µA (typical)
• Efficiency: Up to 98% (depending on load conditions)
• Operating Temperature Range: 0°C to +70°C (commercial grade)
• Package Types: DIP-8, SOIC-8

The ICL7660 is an 8-pin IC. Below is the pinout and description:

1. Power Supply: Connect the positive voltage supply (1.5V to 10V) to the V+ pin (Pin 1 and Pin 8). Connect the GND pin (Pin 3) to the ground of the circuit.
2. Charge-Pump Capacitors:
   • Connect a 10µF capacitor between CAP+ (Pin 2) and CAP- (Pin 4).
   • Connect another 10µF capacitor between VOUT (Pin 5) and GND (Pin 3).
   • Ensure the capacitors are rated for at least twice the input voltage for reliability.
3. Low Voltage Operation: If the input voltage is below 3.5V, connect the LV pin (Pin 6) to GND to optimize performance.
4. Oscillator Control: Leave the OSC pin (Pin 7) unconnected for the default operating frequency (10kHz). For custom frequency control, refer to the datasheet.

• Capacitor Selection: Use low-ESR capacitors (e.g., ceramic or tantalum) for optimal performance.
• Load Current: Avoid exceeding the maximum output current (40mA) to prevent voltage drop and inefficiency.
• Bypass Capacitor: Place a 0.1µF ceramic capacitor close to the V+ pin to reduce noise and improve stability.
• Thermal Management: Ensure adequate ventilation or heat dissipation if operating near the maximum current limit.

The ICL7660 can be used to generate a negative voltage for powering an op-amp in an Arduino-based project. Below is an example:

/* Example: Using ICL7660 to generate -5V for an op-amp in an Arduino project.
   This code demonstrates reading an analog signal and outputting a processed
   signal using an op-amp powered by the ICL7660. */

// Define the analog input and output pins
const int analogInputPin = A0;  // Analog input pin for the signal
const int analogOutputPin = 9; // PWM output pin for processed signal

void setup() {
  pinMode(analogInputPin, INPUT);  // Set the input pin mode
  pinMode(analogOutputPin, OUTPUT); // Set the output pin mode
  Serial.begin(9600); // Initialize serial communication for debugging
}

void loop() {
  int sensorValue = analogRead(analogInputPin); // Read the analog input
  int outputValue = map(sensorValue, 0, 1023, 0, 255); 
  // Map the input value to a PWM range (0-255)

  analogWrite(analogOutputPin, outputValue); // Output the processed signal
  Serial.println(outputValue); // Print the output value for debugging
  delay(10); // Small delay for stability
}

• The ICL7660 provides the negative voltage rail (-5V) required by the op-amp in this circuit.
• Ensure proper decoupling capacitors are used for both the ICL7660 and the op-amp.

1. Output Voltage is Incorrect or Unstable:

   • Verify the charge-pump capacitors are correctly connected and have the proper value (10µF).
   • Check for low-ESR capacitors; high ESR can cause instability.
   • Ensure the input voltage is within the specified range (1.5V to 10V).

2. Excessive Voltage Drop Under Load:

   • Ensure the load current does not exceed the maximum rating (40mA).
   • Use larger capacitors (e.g., 22µF) to improve load regulation.

3. IC Overheating:

   • Reduce the load current if it exceeds the recommended operating range.
   • Check for proper ventilation or heat dissipation.

4. No Output Voltage:

   • Verify all connections, especially the charge-pump capacitors.
   • Ensure the LV pin is connected to GND if the input voltage is below 3.5V.

Q1: Can the ICL7660 generate a positive voltage?
A1: No, the ICL7660 is specifically designed to invert a positive voltage to a negative voltage. For positive voltage generation, consider using a boost converter IC.

Q2: What happens if I use capacitors with a lower value than 10µF?
A2: Using smaller capacitors may result in reduced efficiency, increased ripple, and unstable output voltage.

Q3: Can I use the ICL7660 with a 12V input?
A3: No, the maximum input voltage for the ICL7660 is 10V. Exceeding this limit may damage the IC.

Q4: Is the ICL7660 suitable for audio applications?
A4: Yes, but ensure proper filtering to minimize noise introduced by the charge-pump switching.

By following this documentation, users can effectively integrate the ICL7660 into their circuits and troubleshoot common issues.