## Overview of ADG904BRU-R The **ADG904BRU-R** is a high-performance, wideband CMOS **4:1 multiplexer** (SP4T switch) designed by Analog Devices. It is specifically engineered to handle high-frequency signals, making it ideal for RF and microwave applications where low insertion loss and high isolation are critical. --- ### Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Switch Configuration** | SP4T (4-to-1 Multiplexer) | | **Frequency Range** | DC to 2.5 GHz | | **Insertion Loss** | 0.8 dB @ 1 GHz | | **Isolation** | 37 dB @ 1 GHz | | **Power Supply** | 1.65 V to 2.85 V | | **Package Type** | 20-Lead TSSOP | | **Control Logic** | 3.3V / 1.8V CMOS Compatible | | **Operating Temp** | -40°C to +85°C | --- ### Core Electronic Characteristics #### 1. Wideband Performance Unlike standard analog switches, the ADG904 uses a **"T-switch" architecture**. This design minimizes capacitive loading and cross-talk, allowing it to pass signals up to **2.5 GHz** with minimal degradation. #### 2. Absorptive vs. Reflective The ADG904 is an **absorptive switch**. This means that when a channel is in the "OFF" state, the output pins are terminated with a 50 $\Omega$ resistor. This prevents signal reflections back to the source, which is vital for maintaining signal integrity in RF circuits. #### 3. Low Power Consumption Built on a submicron CMOS process, the device consumes extremely low quiescent current (typically less than 1 $\mu$A). This makes it suitable for battery-powered handheld wireless devices. #### 4. Control Logic The device features a 2-bit binary address line ($A0, A1$) and an Enable ($\overline{EN}$) pin. * **A0/A1:** Decides which of the four RF channels is connected to the common RFC port. * **EN:** Disconnects all channels when pulled high. --- ### Typical Applications 1. **Wireless Transceivers:** Switching between different antenna paths or filter banks. 2. **Base Stations:** Routing high-speed data signals in cellular infrastructure. 3. **Test Equipment:** Automated test setups requiring fast, reliable signal routing up to 2.5 GHz. 4. **UWB (Ultra-Wideband):** Systems requiring low distortion across a wide frequency spectrum. --- ### Pin Configuration Summary | Pin Name | Function | | :--- | :--- | | **RF1 - RF4** | The four RF input/output ports. | | **RFC** | The common RF port (connected to one of RF1-RF4). | | **A0, A1** | Binary address bits for channel selection. | | **EN** | Active low enable pin. | | **VDD / GND** | Power supply and ground reference. |