资 源 简 介
The SN54/74LS47 are Low Power Schottky BCD to 7-Segment Decoder/Drivers consisTIng of NAND gates, input buffers and seven AND-OR-INVERTgates. They offer acTIve LOW, high sink current outputs for drivingindicators directly. Seven NAND gates and one driver are connected in pairsto make BCD data and its complement available to the seven decodingAND-OR-INVERT gates. The remaining NAND gate and three input buffersprovide lamp test, blanking input / ripple-blanking output and ripple-blankinginput.The circuits accept 4-bit binary-coded-decimal (BCD) and, depending onthe state of the auxiliary inputs, decodes this data to drive a 7-segment displayindicator. The relaTIve posiTIve-logic output levels, as well as conditionsrequired at the auxiliary inputs, are shown in the truth tables. Outputconfigurations of the SN54/ 74LS47 are designed to withstand the relativelyhigh voltages required for 7-segment indicators.These outputs will withstand 15 V with a maximum reverse current of250 mA. Indicator segments requiring up to 24 mA of current may be drivendirectly from the SN74LS47 high performance output transistors. Displaypatterns for BCD input counts above nine are unique symbols to authenticateinput conditions.The SN54/74LS47 incorporates automatic leading and/or trailing-edgezero-blanking control (RBI and RBO). Lamp test (LT) may be performed at anytime which the BI /RBO node is a HIGH level. This device also contains anoverriding blanking input (BI) which can be used to control the lamp intensityby varying the frequency and duty cycle of the BI input signal or to inhibit theoutputs.
