What is a casual way of saying "I will go offline soon" in an Internet conversation

I’m having a conversation on my phone, but know I can’t answer in a short while (e. g. need to go to sleep of have an appointment). What’s a casual way of saying "I’m going offline soon"? I wanted to say "I’ll have to tune off in 5 min" but apparently that’s not a valid phrase.

With smartphones everyone is online 24/7, so saying "I’m going offline" is technically wrong, it doesn’t feel polite and it doesn’t sound like something a teen would casually say.

Another example: I’m having an online chat but want to focus on school work. I’m not going offline, but I want to focus on the school work instead of the conversation.