While reading through the A3953 (allegro full-bridge PWM motor driver), i came across source drivers and sink drivers. What is a source driver and what is a sink driver? i can't find any references to what are these. Could anyone help me out please? thanks

 

If you look at the functional block diagram on page 2 of the datasheet the bottom transistors (darlington pairs) are the sink drivers and the upper transistors are the source drivers.