I just found it. CHIP does have the same methodology as Medicaid.
For CHIP, Title 42, Regulation §457.315 says to the same methods as §435.603 (which is for Medicaid). As I said above, that is only based on your Adjusted Gross Income (line 11 of your Form 1040).
https://www.law.cornell.edu/cfr/text/42/457.315
https://www.law.cornell.edu/cfr/text/42/435.603
