**ADM1385ARSZ: A Comprehensive Datasheet and Application Overview for the 3V RS-232 Transceiver**

The **ADM1385ARSZ** is a sophisticated, low-power, single-supply **3V RS-232 transceiver** from Analog Devices, designed to facilitate robust serial communication in space-constrained and power-sensitive applications. As a complete serial port solution, it integrates two drivers and two receivers on a single monolithic chip, fully complying with the stringent EIA-232E and V.28/V.24 communication standards.

**Key Features and Electrical Characteristics**

Housed in a compact 20-lead SSOP package, the ADM1385ARSZ is engineered for **exceptional performance and reliability**. A primary advantage is its operation from a **single +3.0V to +3.6V power supply**, making it ideal for battery-powered and portable devices such as handheld test equipment, PDAs, and mobile phones. Despite the low supply voltage, the device generates the necessary ±5.5V RS-232 output voltages internally through an efficient on-chip charge pump, requiring only four small external 0.1 µF capacitors.

The transceiver boasts a high data rate capability, supporting signals up to **460 kbps**, which ensures compatibility with a wide range of baud rates. Its drivers are protected against short circuits and can survive multiple fault conditions, enhancing system durability. Furthermore, the device features a low-power shutdown mode, where the supply current drops to less than 1 µA, a critical attribute for maximizing battery life.

**Internal Architecture and Functionality**

The internal architecture of the ADM1385 consists of a **dual charge-pump voltage converter**, the driver and receiver sections, and a level-shifting transmitter. The charge pump utilizes a switching architecture to generate the positive and negative voltages required for true RS-232 signaling from the single low-voltage supply. The receivers convert RS-232 input signals to 3V CMOS/TTL logic levels, while the drivers perform the inverse operation, converting logic levels to RS-232 outputs.

**Typical Application Circuits**

The ADM1385ARSZ simplifies design-in, typically used to interface a UART (Universal Asynchronous Receiver/Transmitter) with an RS-232 port. A standard application circuit involves connecting the UART's transmit (T xD) and receive (R xD) lines to the driver inputs and receiver outputs of the ADM1385, respectively. The four charge-pump capacitors are connected to their designated pins. The /ENABLE and /SHDN pins provide control for enabling the drivers and entering the ultra-low-power shutdown mode. It is commonly deployed in **point-of-sale terminals, industrial controllers, and embedded systems** requiring a serial debug port.

**Design Considerations and Best Practices**

For optimal performance and EMI compliance, careful PCB layout is essential. The **charge-pump capacitors must be placed as close as possible to the IC** to minimize parasitic inductance and ensure efficient operation. Additionally, bypass capacitors on the power supply line are recommended to filter noise. When operating in electrically noisy environments, the robust ESD protection of the ADM1385 (typically ±15 kV on the I/O lines per Human Body Model) safeguards the connected data terminal equipment.

**ICGOODFIND**

The ADM1385ARSZ stands out as a highly integrated and efficient solution for modern 3V system-level serial communication. Its combination of a **single low-voltage supply, compact form factor, and robust feature set** makes it an exceptional choice for designers seeking to implement reliable RS-232 interfaces without compromising on power consumption or board space.

**Keywords:** RS-232 Transceiver, Single 3V Supply, Low-Power Shutdown, Charge Pump, ESD Protection