Knowing the parameters that determine the performance of analog SWITCHES makes circuit design easier! | NEXTY Electronics, an electronic components and semiconductor trading company

What is an analog SWITCHES?

For example, analog SWITCHES are primarily used when you want to insert SWITCHES into a circuit, such as for switching LEDs, POWER SUPPLIES supplies, audio signals on and off, or analog signals. Analog SWITCHES are connected in series with electrical signals or POWER SUPPLIES lines and can switch between ON and OFF states. While SWITCHES have mechanical contacts, this explanation will focus on analog SWITCHES composed of semiconductor circuits.

Main parameters of analog SWITCHES

When an analog SWITCHES is in the ON position, it behaves as a resistive component, and parasitic capacitance is also added. Therefore, when used in high-speed data transmission lines in particular, care must be taken regarding signal attenuation. Furthermore, because the structure allows some leakage current and noise to be transmitted even when SWITCHES is OFF, understanding the parameters of analog SWITCHES allows for the selection of appropriate components and the implementation of countermeasures in advance when designing actual circuits.

POWER SUPPLIES voltage

Products are available ranging from a few volts to over 100 volts. Furthermore, for the negative POWER SUPPLIES, there are types that support not only GND but also other negative voltages.

ON resistance

This is the resistance between the source and drain of MOS FETS when it is ON. For applications where very little current flows, the ON resistance is not a major concern. However, for applications where a certain amount of current flows, power loss across this resistance must be considered. Furthermore, when dealing with AC signals or when the signal is amplified in a subsequent stage, this ON resistance can affect the signal, so caution is necessary. The ON/OFF state of the nch and pch changes depending on the input voltage, and the ON resistance changes accordingly, so this point also needs to be considered.

Capacity

This is the parasitic capacitance value visible from the input TERMINALS. In addition to parasitic capacitance due to the physical structure of the IC, there is also parasitic capacitance due to the gate capacitance (CGD and CGS) of MOS FETS. When trying to lower the ON resistance of MOS FETS, the gate area increases, and consequently the gate capacitance increases, so there is basically a trade-off between low ON resistance and low gate capacitance (parasitic capacitance). In high-frequency applications, this parasitic capacitance cannot be ignored.

Charge injection

The charge stored in the parasitic capacitance (CGD and CGS) of MOS FETS is charged and discharged when SWITCHES is turned ON/OFF, causing a spike voltage in the signal line. To reduce this spike voltage, choose a product with low charge injection or take measures such as connecting a capacitor between the output and GND.

Leakage current

This is the leakage current that flows between the source and drain of MOS FETS when SWITCHES is OFF. Leakage current inevitably causes some loss. Furthermore, if an ADC is connected downstream, for example, the leakage current can affect the analog signal. Leakage current varies with temperature and POWER SUPPLIES voltage.

Off-isolation

The magnitude of the input signal leaking to the output when SWITCHES is OFF. Expressed as a negative decibel value.

Inter-channel crosstalk

In products with multiple channels, this refers to the amount of AC signal component leakage from one channel into other channels. It is expressed as a negative decibel value.

Others

SWITCHES ON/OFF control methods range from those using SWITCHES ON/OFF TERMINALS to those using digital communication such as I2C and SPI communication.