Fairchild is the premier supplier for switch products for use in portable and consumer applications. Our Analog, Audio, Video and USB switches are used to minimize redundant circuitry, eliminate connectors, allow for design flexibility in feature offerings and to save space in your design. Offered in a variety of functions, configurations, packages and performance levels, Fairchild switches can help you solve your specific design challenges.
1. Should an analog switch be selected primarily based on On Resistance (Ron)?
A. No. On resistance is very important but each application is unique and the trade-off between Ron and Con needs to be fully understood. Low Ron (1 ohm or less) devices will have greater on-capacitance so for capacitive sensitive, high frequency or high speed data rate applications the low Con is the more critical parameter.
2. What is Ron Flatness for an Analog Switch?
A. Ron (flatness) is a measure of the “peak” and “valley” of the composite analog switch Ron. If this parameter is large then the composite, Ron can cause variable attenuation, which is particularly bad for audio applications. The FSA-family of switches are specifically designed to minimize this variable attenuation. A low Ron (flatness) also results in excellent THD characteristics (Total Harmonic Distortion).
3. When I apply a lower voltage to the switch control pin than what is applied to Vcc, my application consumes a significant amount of current, how can I resolve this?
A. For this application scenario the devices needed are those that are defined as “Low Icct”. Low-Icct devices are our A-version devices (for example, FSA2267A) or on newer generation products they will simply have an Icct specification in the datasheet (for example, FSA2156). Products with low Icct minimize power consumption without the need of a voltage translator. (for additional information, please read applications note AN-5064)
4. Can an analog switch pass a digital signal?
A. Yes, an analog switch can pass a digital signal. Since the analog switch is an NMOS/PMOS transmission gate there is also no voltage translation or clamping action so the preferred choice may be the analog switch over a digital switch.