The electrical interface is quite simple, as illustrated in Figure 9-1. Connect the OPT3004 I²C SDA and SCL pins to the same pins of an applications processor, microcontroller, or other digital processor. If that digital processor requires an interrupt resulting from an event of interest from the OPT3004, then connect the INT pin to either an interrupt or general-purpose I/O pin of the processor. There are multiple uses for this interrupt, including signaling the system to wake up from low-power mode, processing other tasks while waiting for an ambient light event of interest, or alerting the processor that a sample is ready to be read. Connect pullup resistors between a power supply appropriate for digital communication and the SDA and SCL pins (because they have open-drain output structures). If the INT pin is used, connect a pullup resistor to the INT pin. A typical value for these pullup resistors is 10 kΩ. The resistor choice can be optimized in conjunction to the bus capacitance to balance the system speed, power, noise immunity, and other requirements.

The power supply and grounding considerations are discussed in the Power-Supply Recommendations section.

Although spike suppression is integrated in the SDA and SCL pin circuits, use proper layout practices to minimize the amount of coupling into the communication lines. One possible introduction of noise occurs from capacitively coupling signal edges between the two communication lines themselves. Another possible noise introduction comes from other switching noise sources present in the system, especially for long communication lines. In noisy environments, shield communication lines to reduce the possibility of unintended noise coupling into the digital I/O lines that could be incorrectly interpreted.