Rhoys Wiggins came closest to equalising for Charlton but his 30th-minute shot was palmed on to the post by Ipswich goalkeeper Dean Gerken.
McCarthy said: "We've played better than that away and lost games.
"The three points is the biggest plus, then winning away and then the clean sheet.
"I wanted to approach it with a real fast start, we could have been 2-0 up in the first few minutes.
"And then we've had a good defensive performance and kept a clean sheet.
"Tommy and Christophe (Berra) had to put in real battling performances as their front two were a handful. Simon Church looks like he has found his mojo again.
"I thought we handled Cameron Stewart well and Aaron Cresswell was great in his first game back.
"This league will be tight until the end. Look at Doncaster losing to Charlton in midweek and then beating QPR today.
"It will be 50-odd points to stay up again and anyone of us can beat anyone else and that is what makes it such a tough evil league to play in."