The default I2C address is 0x4C.

Power Pins

• VIN - this is the power pin. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V microcontroller like Arduino, use 5V. It also needs to have the same voltage as the highest signal you are switching. That means if the analog signals are no more than 5VDC, the VIN pin must be higher than 5V. You cannot power this pin with 3.3V and switch 5V signals.
• GND - common ground for power and logic.

I2C Logic Pins

• SCL - I2C clock pin, connect to your microcontroller's I2C clock line. This pin can use 3-5V logic, and there's a 10K pullup on this pin.
• SDA - I2C data pin, connect to your microcontroller's I2C data line. This pin can use 3-5V logic, and there's a 10K pullup on this pin.
• STEMMA QT - These connectors allow you to connectors to dev boards with STEMMA QT (qwiic) connectors or to other things with various associated accessories

Analog Switch Pins

• S1-S8 - The 8 switch channels. Unlike digital switches and multiplexers, these channels are not strictly 'inputs' or 'outputs' because the signal is bidirectional.
• D - The analog pin for the switch. D can act as input or an output. It can be an input to the 8 channel outputs, or the 8 channel inputs can be output to D.

This breakout isn't really a 'selecting multiplexer', a matrix switch with 8 independent switches. You could treat it like an SP8T where you select which of the 8 channels are routed to the D pin. You can also turn on multiple channels to 'merge' the signals together.

There are a few things to keep in mind when using these pins:

• The switch signals cannot be below ground. No negative voltages can be applied to the Switch or D pins!
• Analog switches are for signals, not power! Since this is not a mechanical switch, the signals pass through circuitry that is not designed to source or sink current. This is great for analog signal voltages, and is not good for providing more than a few mA of current.

Address Pins

On the back of the board are two address jumpers, labeled A0 and A1. These jumpers allow you to chain up to 4 of these boards on the same pair of I2C clock and data pins. To do so, you solder the jumpers "closed" by connecting the two pads.

On the front of the board are two address pins, labeled A0 and A1. Just like the jumpers, these pins allow you to change the I2C address to connect multiple boards by connecting them to VIN.

The default I2C address is 0x4C. The other address options can be calculated by "adding" the A0/A1 to the base of 0x4C.

A0 sets the lowest bit with a value of 1 and A1 sets the next bit with a value of 2. The final address is 0x4C + A1 + A0 which would be 0x4F.

If only A0 is soldered closed, the address is 0x4C + 1 = 0x4D

If only A1 is soldered closed, the address is 0x4C + 2 = 0x4E

The table below shows all possible addresses, and whether the pin(s) should be high (closed) or low (open).

Reset Pin

• RST - This is the reset pin for the ADG728. You can tie it to GND to immediately set all the switch channels to open.

Power LED and LED Jumper

• Power LED - In the upper left corner, above the STEMMA connector, on the front of the board, is the power LED, labeled on. It is a green LED.
• LED jumper - This jumper is located on the back of the board, in the upper right corner. It's labeled LED on the board silk. Cut the trace on this jumper to cut power to the "on" LED.