Power Pins

• V+ - power input for the MAX4544. It is the red wire on the JST PH cable. You can use 3-12VDC. The voltage must as high as the highest analog voltages you want to switch. That means if the analog signals are no more than 6VDC, the V+ pin must be higher than 6V. You cannot power this pin with 3.3V and switch 12V signals.
• - - common ground for power and logic.

Selection Signal Input

• SIG - this is the selection signal input for the MAX4544. It expects a digital (high or low) signal from your microcontroller with a minimum logic level of 2.5VDC. When it is low, the Common pin is connected to the Normally Closed (NC) pin and disconnected from the Normally Open (NO) pin. When it is high, the Common pin is connected to NO and disconnected from NC.

STEMMA JST PH

• STEMMA JST PH - 2mm pitch STEMMA JST port for use with 3-pin STEMMA JST PH cables. It has connections for:
  • GND/- - common ground for power and data. It is the black wire on the JST PH cable.
  • V+ - power input for the MAX4544. It is the red wire on the JST PH cable. 
  • SIG - signal from your microcontroller. It needs to be have a minimum 2.5VDC logic level. It is the white wire on the JST PH cable.

Analog Switch Inputs and Output

You'll connect your analog signals to NO and NC. The state of the SIG pin will determine which analog signal is output to common.

These pins expect an analog signal voltage, not a power voltage. Since this is not a mechanical switch, the signals pass through circuitry that is not designed to source or sink current. Additionally, the MAX4544 cannot switch signals below ground. No negative voltages can be applied to these pins.

• NO - this is the Normally Open pin. It is connected to the common pin when the SIG pin is high.
• NC - this is the Normally Closed pin. It is connected to the common pin when the SIG pin is low.
• COM - this is the common output from the MAX4544 switch. The selected analog signal from NO or NC will be output to this pin.

These pins are available along the side edge of the board or via the 3-pin terminal block.

Signal LED and Jumper

• Signal LED - to the left of the JST PH connector is the signal LED, labeled Sig. It is the red LED. It will light up when SIG is high and turn off when SIG is low.
• LED jumper - in the upper right corner on the back of the board is a jumper for the signal LED. It is labeled SIG on the board silk. If you want to disable the signal LED, cut the trace on this jumper.

Power LED and Jumper

• Power LED - to the right of the JST PH connector is the power LED, labeled ON. It is the green LED.
• LED jumper - in the upper left corner on the back of the board is a jumper for the power LED. It is labeled ON on the board silk. If you want to disable the power LED, cut the trace on this jumper.