Story highlights Peter Robbins, 56, is charged with 12 felony counts of making threats and stalking

He is ordered to stay away from his ex-girlfriend and a La Jolla plastic surgeon

Border Patrol agents arrested Peter Robbins late Sunday as he entered the U.S. from Mexico

Robbins was 9 in 1965 when he voiced Charlie Brown in the animated TV movies

Peter Robbins was a child when he provided the iconic voice for Charlie Brown, still heard every year when the classic 1960s television movies are rebroadcast.

Today, Robbins is in the San Diego County jail, inmate No. 13704837, charged with 12 felony counts of making criminal threats and stalking, authorities said.

Robbins, 56, of Oceanside, California, pleaded not guilty Wednesday to the charges in San Diego County Superior Court, said District Attorney Bonnie Dumanis. Robbins is facing up to nine years in state prison for stalking his ex-girlfriend and making criminal threats against a La Jolla plastic surgeon, the prosecutor said.

San Diego Superior Court Judge David Szumowski set Robbins' bail at $550,000, and he was ordered to have no contact with the two people involved in the case and not to possess a gun, Dumanis said.

A readiness hearing for Robbins has been set for February 22 and a preliminary hearing has been scheduled for March 22.

Border Patrol agents arrested Robbins late Sunday as he entered the United States from Mexico at the San Ysidro, California, port of entry, according to a U.S. Customs and Border Protection spokesman.

A computer check of his passport revealed that Robbins, who was driving into the country alone in a 2006 Mercedes, was wanted in San Diego on a felony warrant, Customs spokesman Ralph DeSio said.

Robbins acknowledged to police that he is the same Peter Robbins who was the child actor, San Diego Police spokesman Gary Hassen said.

The four counts of threatening death and one stalking charge involve four victims, including a San Diego Police sergeant. Robbins allegedly threatened the officer with bodily harm during a January 13 incident, Hassen said.

Police in Oceanside and Carlsbad, California, are also investigating incidents there, Hassan said.

CNN was unable to contact Robbins or a representative for comment.

Robbins was 9 in 1965 when he was cast as Charlie Brown in the animated "A Boy Named Charlie Brown." "A Charlie Brown Christmas" was produced later that year, using Robbins as the lead voice. Other TV movies using Robbins' voice include "Charlie Brown's All Stars!" "It's the Great Pumpkin, Charlie Brown," "You're in Love, Charlie Brown" and "He's Your Dog, Charlie Brown."

His last role as Charlie Brown -- "It Was a Short Summer, Charlie Brown" -- was produced when Robbins was 13.

He told an interviewer in 2008 that he was replaced when his voice changed too much after he turned 14.

Robbins' on-camera acting career included featured roles in episodes of TV's "Rawhide," "The Munsters," "F Troop" and "Get Smart."

Robbins' last acting role was in a 1972 episode of "My Three Sons," according to the Internet Movie Database.

He grew up to become a California real estate agent, living in Oceanside with his dog, Snoopy, his official biography said.