0 Replies Latest reply on Jun 22, 2011 10:44 AM by content.librarian

    Reason for VOH and VOL not specified in Programmable Clocks Datasheets

    content.librarian

      As can be seen VOH and VOL specifications for programmable clocks are not specified. In the Electrical Characteristics table of CY22393, for example, lists IOH with a condition of VOH=(L)VDD-0.5, (L)VDD = 3.3V. For this condition when VOH = 2.8V (3.3V-0.5V), Cypress guarantees that there will be at least 12mA of current being driven from our part. The 12mA is a minimum specification that the designers need to design to. It is a minimum value chosen by design and marketing that Cypress can guarantee the part will drive. Most likely there will not be a case where the driver will only source/sink 12mA.    

                

         

      The outputs are tested by setting the clock output voltage to either GND (IOL) or VCC (IOH) and using external equipment to sweep the voltage from 0 to VCC and measure the current at each voltage step. This produces I-V curves where Cypress looks to see what the minimum current is at the specified voltage. In this case 2.8V has a minimum of 12mA under worst case conditions, but normally is around 24mA.     

                

         

      Cypress does not specify the other way around specifying a current and state the voltage level.