Dynamic font rendering issue on xhdpi Android Devices

I implement my own font rendering system in Unity. Its works fine in all cases except running on Android devices with xhdpi pixel density. In log i can see that Unity invokes updateTexture callback, but when i try to font.GetCharacterInfo(...) is returns true and fill CharacterInfo structure with wrong data. All this works fine on Web, Editor, Win/Mac Standalone, IOS and Android devices with hdpi and less pixel density. For example its doesn't work on Nexus 4.