**ADM660ARZ-REEL7: A Comprehensive Guide to the Switched-Capacitor Voltage Converter**

In the world of electronic design, power management is a critical challenge, especially when dealing with space-constrained or battery-powered applications. The **ADM660ARZ-REEL7**, a switched-capacitor voltage converter from Analog Devices, stands out as a versatile and efficient solution for DC-DC conversion. This integrated circuit (IC) is specifically engineered to generate a negative output voltage from a positive input or to double the input voltage, all without the need for bulky inductors.

**Understanding the Switched-Capacitor Architecture**

Unlike traditional switching regulators that rely on inductors to store and transfer energy, the ADM660ARZ-REEL7 utilizes a **switched-capacitor charge pump** topology. This method employs capacitors as the primary energy storage elements. The internal operation is elegantly simple: an internal oscillator controls MOSFET switches that alternately connect an external flying capacitor (C1) to the input voltage for charging and then to an output storage capacitor (C2) for discharging. This switching action, typically at a frequency of 25 kHz, effectively "pumps" charge to the output, thereby inverting or doubling the input voltage.

**Key Features and Specifications**

The ADM660ARZ-REEL7 is packed with features that make it a preferred choice for designers:

* **Wide Input Voltage Range:** It operates from a **+1.5V to +7V** input, making it compatible with a variety of power sources, including single-cell Li-ion batteries (+3.7V) and standard 5V rails.

* **Output Options:** It can be configured to provide a **negative output voltage (-VIN)** or a **positive output voltage of approximately +2VIN**.

* **Low Power Consumption:** The device boasts a low supply current of 120 µA (typical), which is crucial for extending battery life in portable devices.

* **No Inductors Required:** The absence of magnetic components minimizes **electromagnetic interference (EMI)**, reduces solution size, and simplifies board layout.

* **Compact Package:** Housed in an 8-lead SOIC package, it is ideal for applications where PCB real estate is limited.

**Typical Applications**

The unique capabilities of the ADM660ARZ-REEL7 make it suitable for a diverse range of applications:

* **Generating Negative Supply Rails:** Providing a negative bias voltage for operational amplifiers, sensors, and data acquisition systems in single-supply setups.

* **RS-232 Interface Systems:** Powering the negative voltage required for traditional serial communication interfaces from a single +5V or +3.3V supply.

* **LCD Bias Generation:** Creating the negative voltage layers needed for liquid crystal displays (LCDs).

* **Portable and Battery-Powered Equipment:** Doubling a low battery voltage to power other components or creating a small negative rail for audio circuits in devices like data loggers, medical instruments, and handheld meters.

**Design Considerations and Layout Tips**

To ensure optimal performance, several factors must be considered:

1. **Capacitor Selection:** Use low-ESR (Equivalent Series Resistance) ceramic capacitors for both the flying (C1) and output (C2) capacitors. Values between 10 µF and 100 µF are typical.

2. **Output Current:** The available output current decreases as the input voltage drops. Designers must check the output drive capability in the datasheet to ensure it meets the load requirements.

3. **Output Ripple:** The switched-capacitor operation inherently creates output ripple voltage. Proper capacitor selection and a clean PCB layout are essential to minimize this effect. Placing C1 and C2 as close as possible to the IC's pins is critical.

**ICGOODFIND**

The ADM660ARZ-REEL7 is an exceptionally efficient and compact solution for DC-DC conversion tasks that involve voltage inversion or doubling. Its inductorless design simplifies EMI mitigation and reduces the overall footprint, making it a superior choice for space-sensitive and portable applications. For engineers seeking a reliable, simple, and cost-effective power management IC, the ADM660ARZ-REEL7 represents a compelling option.

**Keywords:**

Switched-Capacitor, Voltage Converter, Charge Pump, Negative Voltage, DC-DC Conversion