Tatramajjhattatā • Equanimity • In the middle of all that

Friends, could anybody direct me to some suttas of the pâli canon about **Tatramajjhattatā**, the developed form of the equanimous abiding 'in the middle of all that'. To the best of my knowledge, this specific mental factor is mentioned in the ***Abhiddhamma*** and the ***Visuddhimagga***, but I was unable to find it referred to in the Pali Canon. Many thanks for your much appreciated help, with Mettā