74LS168 DIP 4-Bit Synchronous Decade Up-Down Counter
The 74LS168 is a high speed TTL integrated circuit that functions as a fully synchronous 4-bit up-down decade counter. This device counts in a Binary Coded Decimal (BCD) sequence from 0 through 9 and features an internal carry look-ahead for high-speed counting. All state changes, including the count direction and parallel loading, are synchronized to the positive-going transition of the clock pulse, ensuring a stable and glitch-free output.
This IC includes a mode control input that determines whether the counter increments or decrements. It is also fully presettable, allowing any BCD value to be loaded into the counter via parallel data inputs when the load line is active low. The 74LS168 is designed for easy cascading; it provides a ripple carry output and two enable inputs to facilitate the creation of multi-decade counting systems without the need for additional external gates.
KEY FEATURES
- Synchronous counting for high-speed digital timing
- Reversible counting direction (Up/Down control)
- Fully presettable for programmable starting values
- Internal look-ahead carry for fast cascading
- BCD decade sequence for digital display systems
- Standard 16 pin dual in line package
SPECIFICATIONS
- Supply Voltage 4.75V to 5.25V
- Operating Temperature 0 to 70 Celsius
- Logic Type TTL Low Power Schottky
- Maximum Clock Frequency 25MHz
- Typical Power Dissipation 100mW
- High Level Output Current -0.4mA
- Low Level Output Current 8mA
INTERFACES
- CLK Clock input positive edge triggered
- U/D Up-down count control input
- LOAD Parallel load input active low
- ENP Count enable P input
- ENT Count enable T input for carry logic
- A B C D Parallel data inputs
- QA QB QC QD BCD counter outputs
- RCO Ripple carry output active low
- VCC Positive supply voltage
- GND Ground reference
