It works now with out the diode, I added the diode based on their datasheet's sample circuit for bipolar input. Anyways, the output has about the same jitter as the TTL provided by the driver, except that the zero triggering is a bit off. This makes me think that the source since wave itself has some jitter to it. The jitter lowers as the amplitude of the sine wave increases.
Is there any other ideal solution for this problem or maybe I should just live with it.