DM54LS491/74LS491 10-Bit Counter General Description Features/Benefits The ten-bit counter can count up, count down, set, and load 2 LSB’s, 2 MSB’s and 6 middle bits high or low as a group. All operations are synchronous with the clock. SET overrides LOAD, COUNT and HOLD. LOAD overrides COUNT. COUNT is conditional on CIN, otherwise it holds. All outputs are enabled when OE is low, otherwise HIGH-Z. The 24 mA IOL outputs are suitable for driving RAM/PROM address lines in video graphics systems. Y Connection Diagram Standard Test Load Y Y Y Y CRT vertical and horizontal timing generation Bus-structured pinout 24-pin SKINNYDIP saves space TRI-STATEÉ outputs drive bus lines Low current PNP inputs reduce loading Top View TL/L/8332 – 2 TL/L/8332 – 1 Order Number DM54LS491J, DM74LS491J or DM74LS491N See NS Package Number J24F or N24C Function Table OE CK SET LD CNT CIN UP D9-D0 H L L L L L L X u u u u u u X H L L L L L X X L H H H H X X X H L L L X X X X H L L X X X X X L H X X D X X X X Q9-Q0 Operation Z Hi-Z H Set all HIGH D LOAD D Q HOLD Q HOLD Q plus 1 Count UP Q minus 1 Count DN TRI-STATEÉ is a registered trademark of National Semiconductor Corp. C1995 National Semiconductor Corporation TL/L/8332 RRD-B30M115/Printed in U. S. A. DM54LS491/74LS491 10-Bit Counter July 1989 Absolute Maximum Ratings Off-State Output Voltage If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Supply Voltage VCC 5.5V Storage Temperature b 65§ to a 150§ C 7V Input Voltage 5.5V Operating Conditions Symbol Military Parameter VCC Supply Voltage TA Operating Free-Air Temperature tw Width of Clock Min Typ 4.5 5 b 55 Commercial Min Typ Max 5.5 4.75 5 5.25 V 125* 0 75 §C High 40 40 Low 35 35 tSU Set-Up Time 60 th Hold Time 0 Units Max ns 50 b 15 ns 0 b 15 Min Typ ² * Case temperature Electrical Characteristics Over Operating Conditions Symbol Parameter VIL Low-Level Input Voltage VIH High-Level Input Voltage Test Conditions Max Units 0.8 V 2 VIC Input Clamp Voltage IIL Low-Level Input Current VCC e MAX VI e 0.4V b 0.25 IIH High-Level Input Current VCC e MAX VI e 2.4V 25 mA II Maximum Input Current VCC e MAX VI e 5.5V 1 mA VOL Low-Level Output Voltage VCC e MIN VIL e 0.8V VIH e 2V 0.5 V VOH IOZL High-Level Output Voltage Off-State Output Current IOZH VCC e MIN VIL e 0.8V VIH e 2V II eb18 mA V VCC e MIN MIL IOL e 12 mA COM IOL e 24 mA MIL IOH eb2 mA COM IOH e 3.2 mA VCC e MAX VIL e 0.8V VIH e 2V VO e 2.4V VO e 0V IOS Output Short-Circuit Current* VCC e 5.0V ICC Supply Current VCC e MAX b 1.5 V mA 2.4 V VO e 0.4V b 100 b 30 120 mA 100 mA b 130 mA 180 mA * No more than one output should be shorted at a time and duration of the short-circuit should not exceed one second. ² All typical values are at VCC e 5V, TA e 25§ C Switching Characteristics Over Operating Conditions Symbol Parameter fMAX Maximum Clock Frequency tPD Clock to Q tPZX Output Enable Delay tPXZ Output Disable Delay Test Conditions (See Test Load) Military Min Commercial Typ Max 20 R1 e 200X R2 e 390X 2 Units Typ Max 35 20 30 ns 35 55 35 45 ns 35 55 35 45 ns 10.5 CL e 50 pF Min 12.5 MHz Logic Diagram 10-Bit Up/Down Counter TL/L/8332 – 3 3 DM54LS491/74LS491 10-Bit Counter Physical Dimensions inches (millimeters) 24-Pin Narrow Ceramic Dual-In-Line Package (J) Order Number DM54LS491J or DM74LS491J NS Package Number J24F 24-Pin Narrow Plastic Dual-In-Line Package (N) Order Number DM74LS491N NS Package Number N24C LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation 1111 West Bardin Road Arlington, TX 76017 Tel: 1(800) 272-9959 Fax: 1(800) 737-7018 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. 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