When the XLAT rising edge is input, all constant current outputs are forced off until the next grayscale display period.
The IC is intended for applications which show static pictures for a longer period of time. So whenever the picture is changing, BLANK can be set high to turn the outputs off and reset the GS counter and during BLANK=high, XLAT can be used to latch the new picture in.If you want to view videos which means that you need to have control over the GS counter to know when to latch in the data, other parts like TLC5941, TLC5943, TLC5946 or TLC5951.
No, only one about the TLC5940. Haven't read the datasheet in detail, but the block diagram looks very different. It looks like the TLC5940 contains an additional EEPROM, you can write to the shift register or the EEPROM and switch the outputs from one to the other. Also, I didn't see a note about the outputs being switched off on latch signal. It also features a grayscale clock output which could probably be used to sync the latch, as mentioned in the TI thread.