**The ADG429BN Quad SPST Monolithic CMOS Analog Switch: Technical Specifications and Application Circuits**
In the realm of precision signal routing and system design, analog switches play a pivotal role. The **ADG429BN from Analog Devices** stands as a prominent solution, offering engineers a robust and versatile component for a wide array of applications. This article delves into the technical specifications and presents common application circuits for this quad single-pole/single-throw (SPST) switch.
**Technical Specifications and Key Features**
The ADG429BN integrates four independent SPST switches on a single monolithic CMOS chip. Its design prioritizes low power consumption and high switching performance, making it suitable for both portable and industrial equipment.
A core feature of this device is its **break-before-make switching action**, which is essential for preventing momentary shorting between signal sources during the switching transition. The switches are **latch-up immune**, a critical characteristic that ensures robustness and protects the device from catastrophic failure caused by overvoltage transients.
Electrically, the ADG429BN excels with its low on-resistance, typically **35 Ohms maximum** across the full specified analog input range. More importantly, this on-resistance exhibits exceptional flatness, typically **4 Ohms**, which is crucial for maintaining signal integrity and minimizing distortion in precision analog applications. The device operates from a **dual power supply of ±15 V or a single supply from +12 V to +15 V**, offering flexibility in system design.
Other notable specifications include:
* **Low Power Consumption:** Typically less than 5 µW, ideal for battery-powered systems.
* **Fast Switching Times:** tON (Turn-On Time) of 150 ns max and tOFF (Turn-Off Time) of 100 ns max.
* **High Off-Channel Isolation:** Typically -80 dB at 10 kHz, minimizing crosstalk between switched channels.
* **TTL/CMOS Compatible Logic Inputs:** Simplifies interface with modern digital controllers and microprocessors.
**Application Circuits**
The quad SPST configuration of the ADG429BN provides immense flexibility. Here are two common application circuits:
1. **Multiplexing/Demultiplexing Analog Signals:** A primary use case is constructing a 4-channel analog multiplexer or demultiplexer. The four switches can be individually controlled by two digital address lines (A0, A1) and an enable pin (EN). This allows a single analog-to-digital converter (ADC) to sequentially sample four different sensor inputs, significantly reducing system cost and complexity. The high off-isolation ensures that signals from inactive channels do not interfere with the selected channel.
2. **Programmable Gain Amplifier (PGA):** The ADG429BN is perfectly suited for implementing a non-inverting PGA. Different feedback resistors (Rf1, Rf2, Rf3, Rf4) are connected between the output of an op-amp and the inputs of the four analog switches. The output of each switch is tied together and connected to the inverting input of the op-amp. By closing one switch at a time, the gain of the amplifier can be digitally selected as Av = 1 + (Rf / Rg), where Rg is a fixed input resistor. The low and flat on-resistance of the switch minimizes gain errors and non-linearity.
**ICGOOODFIND:** The ADG429BN is a highly integrated, precise, and reliable quad SPST analog switch. Its combination of **low and flat on-resistance, fast switching speed, and latch-up immunity** makes it an exceptional choice for a multitude of signal routing tasks, from data acquisition systems and audio routing to automated test equipment and programmable instrumentation. Its ability to simplify circuit design while enhancing performance solidifies its value in an engineer's component library.
**Keywords:** **Analog Switch**, **CMOS**, **Low On-Resistance**, **Signal Multiplexing**, **Latch-Up Immune**
