Inter-IC Sound (I2S) is an electrical serial bus standard used for interfacing between digital audio devices. When looking for an I2S analog switch / multiplexer it’s important to understand the specifications of the I2S standard.
- 3-wire push-pull protocol
- Serial Data (SD)
- Word Select (WS)
- Continuous Serial Clock (SCK)
- Voltage Levels
- at present, 5 V TTL is considered a standard for logic levels for I2S. (see [FAQ] What are the VIH and VIL Levels of an Analog Switch / Multiplexer)
- Frequency
- Timing requirements are specified relative to the clock period or to the minimum allowed clock period of a device. This allows room for higher data rates in the future. Typical I2S data rates are <5MHz.
The following are 3 key specifications for your analog switch / multiplexer that will help pick the correct device for your I2S system.
- The configuration of the analog switch / multiplexer. To reiterate, I2S is a 3-wire protocol, therefore a 3-channel device will be needed. To multiplex between exactly 1 controller and 2 target devices, a 3-channel 2:1 device should be placed between the controller and peripherals. Applications are not limited to only 2 target/ 1 controller device configurations. As the number of target/controller devices increase, so does the configuration.
Although not defined by the standard, sometimes applications will use 4-wire interfaces for full-duplex systems. This includes 2 serial data lines (DX, RX), word select (WS) and continuous serial clock (SCK). In the case of 4-wire systems, a 4-channel device will be required.
- Voltage level. Applications are standardized by TTL logic levels listed above. It is important to pick a device that can support this logic level.
- Bandwidth of the device. As stated above, I2S does not have standardized data rates. The timing requirements including clock HIGH (tHC), clock LOW (tLC), delay (tdtr), hold time (thtr), and clock rise-time (tRC) are based off the minimum clock period of your chosen data rate.
For highly sensitive signal chains, best practice is to select a device with 3 x bandwidth – see [FAQ] How do I Select the Right Analog Switch / Multiplexer Bandwidth Based on the Data Rate of my Protocol?
The tables below cover recommendations for switches / multiplexers that can pass I2S signals on data signal paths for 3-wire and 4-wire configuration. These devices are controlled via GPIO.
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I2S Compatible Switches for 1 Controller to 2 Target Devices or 2 Controllers to 1 target device (3-wire) |
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| I2S Voltage Levels |
Supply Voltage Levels |
Device | Configuration | Features | PKG | Body Size (L x W) |
|
3.3 V 5.0 V |
1.8 V 2.5 V 3.3 V 5.0 V |
TMUX1574 |
4-channel 2:1 (SPDT) |
1.8 V Compatible Control Inputs Fail-safe Logic Integrated pulldown resistor on logic pin Powered-off Protection Supports input voltage beyond supply |
SOT-23-THIN | 2.0 mm x 4.2 mm |
|
2:1 x 3 |
1.8-V compatible control inputs |
VQFN |
3.5 mm x 4 mm |
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| 2:1 x 3 |
Break-before-make |
TSSOP |
4.4 mm x 5 mm | |||
|
I2S Compatible Switches for 1 Controller to 2 Target Devices or 2 Controllers to 1 target device (4-wire) |
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| I2S Voltage Levels |
Supply Voltage Levels |
Device | Configuration | Features | PKG | Body Size (L x W) |
|
3.3 V 5.0 V |
1.2 V 1.8 V 2.5 V 3.3 V 5.0 V |
TMUX1575 |
2:1 x 4 |
1.2 V logic compatible 1.8 V logic compatible Powered-off protection Supports input voltage beyond supply |
DSBGA | 1.4 mm x 1.4 mm |
|
2:1 x 4 |
1.8-V logic compatible Supports input voltage beyond supply Integrated pull-down resistor on logic pins Fail Safe logic |
TSSOP |
4.4 mm x 6.5 mm |
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|
1.8 V 2.5 V 3.3 V 5.0 V |
2:1 x 4 |
1.8 V logic compatible Fail-safe logic Integrated pulldown resistor on logic pin Powered-off protection Supports input voltage beyond supply |
SOT-23-THIN |
2 mm x 4.2 mm | ||