© 2000 Fairchild Semiconductor Corporation DS009817 www.fairchildsemi.comOctober 1988Revised March 2000DM74LS47 BCD to 7-Segment Decoder/Driver with Open-Collector OutputsDM74LS47BCD to 7-Segment Decoder/Driver with Open-Collector OutputsGeneral DescriptionThe DM74LS47 accepts four lines of BCD (8421) inputdata, generates their complements internally and decodesthe data with seven AND/OR gates having open-collectoroutputs to drive indicator segments directly. Each segmentoutput is guaranteed to sink 24 mA in the ON (LOW) stateand withstand 15V in the OFF (HIGH) state with a maxi-mum leakage current of 250 µA. Auxiliary inputs providedblanking, lamp test and cascadable zero-suppression func-tions.Features■ Open-collector outputs■ Drive indicator segments directly■ Cascadable zero-suppression capability■ Lamp test input Ordering Code:Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.Logic SymbolVCC = Pin 16GND = Pin 8Connection DiagramPin DescriptionsNote 1: OC—Open CollectorOrder Number Package Number Package DescriptionDM74LS47M M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 NarrowDM74LS47N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 WidePin Names DescriptionA0–A3 BCD InputsRBIRipple Blanking Input (Active LOW)LTLamp Test Input (Active LOW)BI/RBO Blanking Input (Active LOW) orRipple Blanking Output (Active LOW)a –g Segment Outputs (Active LOW) (Note 1)www.fairchildsemi.com 2DM74LS47Truth TableNote 2: BI/RBO is wire-AND logic serving as blanking input (BI) and/or ripple-blanking output (RBO). The blanking out (BI) must be open or held at a HIGHlevel when output functions 0 through 15 are desired, and ripple-blanking input (RBI) must be open or at a HIGH level if blanking or a decimal 0 is notdesired. X = input may be HIGH or LOW.Note 3: When a LOW level is applied to the blanking input (forced condition) all segment outputs go to a HIGH level regardless of the state of any other inputcondition.Note 4: When ripple-blanking input (RBI) and inputs A0, A1, A2 and A3 are LOW level, with the lamp test input at HIGH level, all segment outputs go to aHIGH level and the ripple-blanking output (RBO) goes to a LOW level (response condition).Note 5: When the blanking input/ripple-blanking output (BI/RBO) is OPEN or held at a HIGH level, and a LOW level is applied to lamp test input, all segmentoutputs go to a LOW level.Functional DescriptionThe DM74LS47 decodes the input data in the pattern indi-cated in the Truth Table and the segment identificationillustration. If the input data is decimal zero, a LOW signalapplied to the RBI blanks the display and causes a multi-digit display. For example, by grounding the RBI of thehighest order decoder and connecting its BI/RBO to RBI ofthe next lowest order decoder, etc., leading zeros will besuppressed. Similarly, by grounding RBI of the lowest orderdecoder 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, i.e.: by driving RBI of aintermediate decoder from an OR gate whose inputs areBI/RBO of the next highest and lowest order decoders. BI/RBO also serves as an unconditional blanking input. Theinternal 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 wired-collector logic. A LOW signal thus applied to BI/RBO turnsoff all segment outputs. This blanking feature can be usedto control display intensity by varying the duty cycle of theblanking signal. A LOW signal applied to LT turns on allsegment outputs, provided that BI/RBO is not forced LOW.DecimalInputs Outputsor NoteFunctionLTRBI A3 A2 A1 A0 BI/RBO a b c d e f g0 H H L L L L H L L L L L L H (Note 2)1 H X L L L H H H L L H H H H (Note 2)2 H X L L H L H L L H L L H L3 H X L L H H H L L L L H H L4 H X L H L L H H L L H H L L5 H X L H L H H L H L L H L L6 H X L H H L H H H L L L L L7 H X L H H H H L L L H H H H8 H X H L L L H L L L L L L L9 H X H L L H H L L L H H L L10 H X H L H L H H H H L L H L11 H X H L H H H H H L L H H L12 H X H H L L H H L H H H L L13 H X H H L H H L H H L H L L14 H X H H H L H H H H L L L L15 H X H H H H H H H H H H H HBIX X X X X X L H H H H H H H (Note 3)RBIH L L L L L L H H H H H H H (Note 4)LTL X X X X X H L L L L L L L (Note 5)3 www.fairchildsemi.comDM74LS47Logic DiagramNumerical Designations—Resultant