Robert Casares, 50, was charged with the misdemeanor on Thursday and faces up to a year in jail if convicted, The Orange County Register is reporting.
When he glanced down to secure the computer, he didn't notice traffic had stopped.
He struck a pickup which then hit an Australian family in a crosswalk.
The baby, Ruby Rose Gould, was tossed out of her stroller and killed.
Her mother, Renee, and an 11-year-old girl suffered broken bones.
The Goulds had been visiting family in Orange County at the time of the accident.