SN74LS90DR datasheet by Texas Instruments

SN74LS90DR Frequently Asked Questions (FAQs)

• What is the maximum clock frequency that the SN74LS90DR can handle?
  The maximum clock frequency of the SN74LS90DR is 2.5 MHz, but it can vary depending on the specific application and operating conditions.
• How do I ensure that the SN74LS90DR is properly powered?
  The SN74LS90DR requires a single 5V power supply, and it's essential to ensure that the power supply is clean and stable. A decoupling capacitor of 0.1 μF to 1 μF should be placed close to the device to filter out noise and voltage spikes.
• What is the maximum output current that the SN74LS90DR can sink or source?
  The SN74LS90DR can sink or source up to 16 mA of current per output pin, but it's recommended to limit the current to 10 mA or less to ensure reliable operation.
• How do I handle the asynchronous reset input (R) on the SN74LS90DR?
  The asynchronous reset input (R) should be tied to VCC through a pull-up resistor (typically 1 kΩ to 10 kΩ) to ensure that the device is properly reset. A capacitor (typically 10 nF to 100 nF) can be added in parallel to the resistor to filter out noise.
• What is the recommended layout and routing for the SN74LS90DR?
  To minimize noise and signal degradation, it's recommended to keep the clock signal traces short and away from other signals. Use a ground plane or a power plane to reduce noise and ensure that the device is properly decoupled.