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DM74LS47N BCD to 7-Segment Decoder/Driver with Open-Collecto

2017-09-05 17:22  
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The DM74LS47N 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 maximum leakage current of 250 mA. Auxiliary inputs provided blanking, lamp test and cascadable zero-suppression functions.

DM74LS47N Pinouts



DM74LS47N Features * Open-collector outputs* Drive indicator segments directly* Cascadable zero-suppression capability* Lamp test input DM74LS47N Functional Description


The DM74LS47N decodes the input data in the pattern indicated 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 multidigit 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 highest order decoder, etc., trailing zeros will be suppressed. Leading and trailing zeros can be suppressed simultaneously by using external gates, i.e.: by driving RBI of a intermediate decoder from an OR gate whose inputs are BI/RBO of the next highest and lowest order decoders. BI/RBO also serves as an unconditional blanking input. The internal NAND gate that generates the RBO signal has aresistive pull-up, as opposed to a totem pole, and thus BI/RBO can be forced LOW by external means, using wiredcollector logic. A LOW signal thus applied to BI/RBO turns off all segment outputs. This blanking feature can be used to control display intensity by varying the duty cycle of the blanking signal. A LOW signal applied to LT turns on all segment outputs, provided that BI/RBO is not forced LOW.