# Purpose of the Latch Enable ($\overline{LE}$) and Ripple Blanking ($\overline{BI}$) pins on 74HC4511

I am looking at the datasheet for the 74HC4511 (available here), and I am confused by the usage of two of the pins: Firstly, the "Latch Enable" pin ($\overline{LE}$), and secondly the "Ripple Blanking" pin ($\overline{BI}$).

Looking at the logic table for the IC gives states that if the Latch Enable, is high, and neither of the other two "special pins", $\overline{BI}$ and $\overline{LT}$ are active, then the output is dependent upon the BCD code applied during the transition of $\overline{LE}$ from low to high. Does this mean that it stores the BCD state and continues to output the corresponding 7-segment output (for instance if $0001$ was applied whilst $\overline{LE}$ was transitioning, and then was subsequently changed to $0010$, the 7-segment display would continue to display $1$ rather than $2$?).

I am more confused by the purpose of the Ripple Blanking input, it appears that this simply blanks the 7-segment display, but I do not know what the purpose of this would be, when you can simply set the BCD code to $1111$?)

Thanks in advance, and sorry if this is obvious!

• Thank you very much for your answer; although I'm still not convinced of the usefulness of the blanking input (why it is included when setting $1111$ has the same result). – Thomas Russell Apr 12 '14 at 9:38