Had this situation the other night. Quarterback drops back to pass, he starts scrambling around. A receiver is about 30 yds away from quarterback. He gets hit by a defensive back very hard and goes to ground. It looked like an intent to hurt receiver. I called a personal foul on the defensive back. Did I get it right? The ball was still in quarterbacks hand.

Hard to say without being there, but it would have to be AWFULLY flagrant for me to call it a personal foul if play was still going on. Something perhaps involving a punch or a head-shot.

Rule 9-4-2b and 9-4-2g
 

The rule states, "Charge into or throw an opponent, nor extend the knee to meet the blocker." Or 9-4-2g states "Make any other contact with an opponent which is deemed unnecessary and which incites roughness."

I have a few questions for you?

Was the contact necessary? Was the defender playing football or trying to injure the receiver?

I think you made the right decision. There are many case plays or rulings over the years that suggest he is wrong for his hit. You did the right thing.

Peace

Canadian Philosophy
 

I'm going to issue two penalities for this one.

The first one is illegal contact on an eligible receiver. That's 10 yards. (6.4.10b)

Futhermore, there will be an unnecessary roughenss foul (15 yards and first down) or rough play (25 yards, first down and ejection). Deciding upon or UR or RP is the judgement of the official. Reading your text about looking like an intent to injure, I would rule as RP. (7.2.1)