Charge Pump Voltage Converters: A Guide to the Microchip TC7662BEOA
Voltage conversion is a fundamental requirement in modern electronic design, where components often operate at different voltage levels from the available power supply. Among the various solutions, charge pump voltage converters offer a unique blend of simplicity, efficiency, and compactness, making them ideal for a wide range of applications. The Microchip TC7662BEOA stands as a classic and highly reliable example of this type of integrated circuit.
Unlike inductor-based switching regulators, a charge pump utilizes capacitors as the primary energy storage elements to generate a higher or inverted output voltage. This architecture eliminates the need for bulky, expensive, and potentially noisy inductors. The TC7662BEOA is a monolithic CMOS DC-DC converter that is famously known as a voltage doubler and inverter. Its primary function is to convert a positive input voltage (+1.5V to +12V) into a corresponding negative output voltage (-1.5V to -12V). With minor external component changes, it can also be configured to double a positive input voltage.
The internal operation of the TC7662BEOA is elegantly simple. It consists of a series of electronic switches (typically MOSFETs) that are controlled by an internal oscillator. These switches first connect an external capacitor (the "flying" capacitor) to the input voltage source, charging it. In the next phase of the clock cycle, the switches reconfigure to connect this charged capacitor in series with the input source or to a second external capacitor (the "reservoir" capacitor). This action pumps charge to the output, effectively inverting or doubling the input voltage. The frequency of the internal oscillator (typically 10 kHz) can be increased by adding an external capacitor, which is useful for reducing the size of the external capacitors required or for optimizing performance.
A key advantage of the TC7662BEOA is its exceptional simplicity and low component count. A complete negative voltage generator requires only two inexpensive external capacitors. This makes the solution extremely cost-effective and space-efficient, occupying a minimal footprint on a printed circuit board (PCB). Furthermore, it features high power conversion efficiency, typically exceeding 90% under optimal conditions, and has a very low quiescent current, making it suitable for battery-powered devices.
The applications for this versatile IC are numerous. It is perfectly suited for generating negative supply rails for operational amplifiers, analog sensors, and data acquisition systems. It is also widely used in LCD displays, where a negative bias voltage is required, and in portable equipment where space and weight are at a premium.
The Microchip TC7662BEOA is a quintessential charge pump IC that provides an elegant, inductor-free solution for voltage inversion and doubling. Its hallmark features are its exceptional simplicity, high efficiency, and minimal external component requirement, making it an enduring and popular choice for designers needing a small, reliable, and cost-effective power conversion solution.
Keywords: Charge Pump, Voltage Inverter, DC-DC Converter, Microchip TC7662BEOA, Flying Capacitor
