03-08-2013, 02:06 PM
DM74LS47 BCD to 7-Segment Decoder/Driver with Open-Collector Outputs
Segment Decoder.pdf (Size: 63 KB / Downloads: 12)
General Description
The DM74LS47 accepts four lines of BCD (8421) input
data, generates their complements internally and decodes
the data with seven AND/OR gates having open-collector
outputs to drive indicator segments directly. Each segment
output is guaranteed to sink 24 mA in the ON (LOW) state
and withstand 15V in the OFF (HIGH) state with a maxi-
mum leakage current of 250 μA. Auxiliary inputs provided
blanking, lamp test and cascadable zero-suppression func-
tions.
Functional Description
The DM74LS47 decodes the input data in the pattern indi-
cated in the Truth Table and the segment identification
illustration. If the input data is decimal zero, a LOW signal
applied to the RBI blanks the display and causes a multi-
digit display. For example, by grounding the RBI of the
highest order decoder and connecting its BI/RBO to RBI of
the next lowest order decoder, etc., leading zeros will be
suppressed. Similarly, by grounding RBI of the lowest order
decoder and connecting its BI/RBO to RBI of the next high-
est order decoder, etc., trailing zeros will be suppressed.
Leading and trailing zeros can be suppressed simulta-
neously by using external gates.