How to format an SD Card to FAT16

For a particular device I use, the SD card must be formatted to FAT16. The SD card is 3.94GB

I tried the following. Don't know what to do next:

diskutil unmountDisk disk5s1
Unmount of all volumes on disk5 was successful
sudo newfs_msdos -F 16 /dev/disk5s1
warning: /dev/disk5s1 is not a character device
512 bytes per physical sector
newfs_msdos: FAT16 is impossible for disk size of 3845120KiB