In the realm of electronic design, the generation of stable and inverted voltage rails from a single power source is a common and critical challenge. The **ADM660ANZ**, a monolithic switched-capacitor voltage converter, stands as a robust and versatile solution for such applications. This integrated circuit (IC) simplifies power supply design by efficiently generating a negative output voltage from a positive input, or doubling the input voltage, all without the need for bulky and expensive inductors.

**Understanding the Switched-Capacitor Principle**

At the heart of the ADM660ANZ's operation is a clever **charge-pump mechanism**. Unlike traditional inductor-based switching regulators, this device uses an internal oscillator and a network of switches to control external capacitors. In its most basic mode, it operates in two phases:

1. **Charge Phase:** The external capacitor is charged to the input voltage (V+).

2. **Pump Phase:** The charged capacitor is switched in series with the input voltage and the output, effectively transferring the charge to an output capacitor and generating a negative voltage with respect to ground (VIN - 2*VCAP ≈ -VIN).

This efficient, high-frequency switching (typically around 25 kHz for the ADM660ANZ) allows for a compact and simple design, making it ideal for space-constrained applications.

**Key Features and Specifications**

The ADM660ANZ is distinguished by several important characteristics:

* **Wide Input Voltage Range:** It can operate from a supply voltage between **+1.5V to +7V**, accommodating various power sources from single lithium cells to regulated 5V lines.

* **Configurable Operation:** A single control pin allows the user to select between **voltage inversion** (VOUT = -VIN) and **voltage doubling** (VOUT = 2*VIN) modes, providing significant design flexibility.

* **Output Current Capability:** It can deliver a useful output current of up to **50 mA**, sufficient for powering op-amp circuits, sensors, and other low-power analog sections.

* **Low Power Consumption:** The device features a low quiescent current, which is crucial for battery-powered and portable equipment where extending battery life is paramount.

* **Internal Oscillator and Regulation:** The IC contains a complete internal oscillator and regulator circuit, minimizing external component count. Typically, only two flying capacitors and two reservoir capacitors are required for full operation.

**Typical Application Circuits**

1. **Voltage Inverter:** The most common use case. By connecting the OSC select pin to ground, the device is configured as a voltage inverter. A positive input voltage (e.g., +5V) is efficiently converted to a negative output voltage (e.g., -5V). This is invaluable for providing dual supplies to operational amplifiers, analog-to-digital converters (ADCs), and other ICs that require a negative rail.

2. **Voltage Doubler:** By connecting the OSC select pin to V+, the device switches to voltage doubler mode. An input voltage (e.g., +3.3V) is doubled to a higher output (e.g., +6.6V), useful for powering circuits that require a voltage higher than the available supply.

**Design Considerations and Best Practices**

To ensure optimal performance, several factors must be considered:

* **Capacitor Selection:** The choice of external capacitors is critical. Low-ESR (Equivalent Series Resistance) ceramic capacitors are highly recommended for both the flying (C1, C2) and output (C+) capacitors. Their low ESR ensures high efficiency and minimizes output voltage ripple.

* **PCB Layout:** For best performance, the PCB layout should be as compact as possible. The paths connecting the flying capacitors (C1 and C2) to the IC should be **short and direct** to minimize parasitic inductance and resistance, which can degrade efficiency and increase noise.

* **Load Management:** Designers must be mindful of the device's output current limitations. As the load current increases, the output voltage will droop due to the internal resistance of the charge pump. For loads exceeding 50mA, an alternative solution or an external buffer amplifier may be necessary.

* **Input Decoupling:** A bypass capacitor (typically 10µF) should be placed as close as possible to the V+ and GND pins of the IC to filter noise from the input supply and provide local charge storage.

**Conclusion**

The ADM660ANZ is a highly effective and elegantly simple solution for generating inverted or doubled supply rails. Its **inductor-free design**, combined with a wide operating voltage range and flexible configuration, makes it a perennial favorite among engineers for portable instruments, data acquisition systems, and anywhere a secondary voltage rail is needed without the complexity of a magnetic-based regulator.

**ICGOODFIND:** The ADM660ANZ is an excellent choice for designers seeking a simple, compact, and cost-effective method for generating low-power negative or doubled voltages, eliminating the need for complex switching regulators and inductors.

**Keywords:**

* **Switched-Capacitor**

* **Charge Pump**

* **Voltage Inversion**

* **Inductor-Free**

* **Power Management**