National Semiconductor DM54148 Priority Encoder General Description This TTL encoder features priority decoding of the input data to ensure that only the highest-order data line is en- coded. The DM54148 encodes eight data lines to three-line (4-2-1) binary (octal). Cascading circuitry (enable input E1 and enable output EO) has been provided to allow octal ex- pansion without the need for external circuitry. For ail types, data inputs and outputs are active at the low logic level. Features m@ Encodes 8 data lines to 3-line binary (octal) m@ Applications include: N-bit encoding Code converters and generators Connection Diagram Dual-In-Line Package OUTPUTS Yoo EO GS 3 INPUTS 2 1 #O AG OUTPUT lis lis [14 lis li. [1 {10 | MPPPP PTE 4 5 6 7 & INPUTS. AZ Al GND OUTPUTS TL/F/6545-1 Order Number DM54148J or DM54148W See NS Package Number J16A or W16A Function Table DM54148 Inputs Outputs E1 0 1 2 3 4 5 6 7 A2 Al AO GS EO H xX X x xX X X x x H H H H H L H H H H H H H H H H H H L L x Xx x x xX Xx x L L L L L H L xX X x x x x L H L L H L H L Xx xX X x X L H H L H L L H L xX xX X x L H H H L H H L H L X xX x L H H H H H L L L H L xX X L H H H H H H L H L H L xX L H H H H H H H H L L H L L H H H H H H H H H H L H H = High Logic Level, L = Low Logic Level, X = Dont Care 4-137 srl 148 Absolute Maximum Ratings (noie) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Oftice/Distributors for availability and specifications. Note: The Absolute Maximum Ratings are those values beyond which the safety of the device cannot be guaran- toed. The device should not be operated at these limits. The parametric values defined in the Electrical Characteristics" table are not guaranteed at the absolute maximum ratings. The Recommended Operating Conditions" table will define Supply Voltage 7V Input Voltage 5.5V Operating Free Air Temperature Range DM54 8C to + 125C Storage Temperature Range 6EC to + 150C Recommended Operating Conditions the conditions for actual device operation. Symbol Parameter DM54146 Units Min Nom Max Vec Supply Voltage 4.5 5 5.6 V Vin High Level Input Voltage 2 Vv VIL Low Level Input Voltage 0.8 Vv lou High Level Output Current 0.8 mA lot Low Level Output Current 16 mA Ta Free Air Operating Temperature 55 125 C Electrical Characteristics over recommended operating free air temperature range (uniess otherwise noted) Typ Symbol Parameter Conditions Min (Note 1) Max Units Vi Input Clamp Voltage Voc = Min, || = -12mA 1.5 v Vou High Level Output Voc = Min, lon = Max 24 Vv Voltage Vit = Max, Viq = Min , VoL Low Level Cutput Voc = Min, lo. = Max 04 Vv Voltage Vin = Min, Vip = Max , I Input Current @Max Voc = Max, V; = 5.5V 1 mA Input Voltage hw High Level Input Voc = Max O Input 40 yA Current Vi = 2.4V Others 80 he Low Level Input Voc = Max 0 Input 1.6 Current Vv, = 0.4V mA m* Others 73.2 los Short Circuit Voc = Max (Note 2) 35 85 mA Output Current loot Supply Current Voc = Max (Note 3) 40 60 mA Ioce Supply Current Voc = Max (Note 4) 35 55 mA Note 1: Ail typicals are at Voc = 5V, Ta = 25C. Note 2: Not more than ane output should be shorted at a time. Note 3: ioci is measured with inputs E1 and 7 grounded, other inputs and outputs open. Note 4: loca is Measured with all inputs and all outputs open. 4-138 Switching Characteristics a Voc = 5V and Ta = 25C (See Section 1 for Test Waveforms and Output Load) Symbol Parameter From (Input) Waveform Ri = 4000, CL = 15 pF Units To (Output) Min Max teLH Propagation Delay Time O thru? 15 ns Low to High Level Output to AO, 1,2 In-Phase tPHL Propagation Delay Time Othu7 Output 14 ns High to Low Level Output to AO, 1,2 1PLH Propagation Delay Time O thru 7 19 ns Low to High Level Output to AO, 1,2 Out-of-Phase teHe Propagation Delay Time 0 thru 7 Output 19 ns High to Low Level Output to AO, 1,2 teLH Propagation Delay Time O thru 7 10 ns Low to High Level! Output to 0 Out-of-Phase teHL Propagation Delay Time O thru 7 Output 95 ns High to Low Level Output to EO tpLy Propagation Delay Time O thru 7 30 ns Low to High Level Output to GS In-Phase tPHL Propagation Delay Time Othru7 Output 25 ns High to Low Level Output toGS tpLH Propagation Delay Time E1 to 16 ns Low to High Level Output AG, 1,2 In-Phase . . Output tPHL Propagation Delay Time E1 to 45 ns High to Low Level Output A0,i,2 tPLH Propagation Delay Time Low to High Level Output E1toGs In-Phase 3 ns tPHL Propagation Delay Time 1 toGs Output 15 ns High to Low Level Output teLH Propagation Delay Time Low to High Level Output E1 to E0 In-Phase 18 ns . . Output tPHL Propagation Delay Time E1to EO 30 ns High to Low Levei Output 4-139 ehh 148 Logic Diagram 0) (15) 0 (14) ay) $s 2 (12) 10 5 (13) Al el TL/F /6545-2 4-140