74LS90 is basically a MOD-10 decade counter that generate a BCD output code. It consists of four master-slave JK flip-flop, which are internally connected to provide MOD-2 (count to 2) counter and MOD-5 counter. 74LS90 also have an independent toggle JK flip-flop by CLKA and other three are driven by the CLKB. Typical power dissipation: 45mW\nHigh count rates: 42MHz Choice of counting modes Input Clamp Diodes Limit High-Speed Termination Effect Supply voltage: 5V Operating Ambient Temperature Range: 55 to 125C Equivalents 74LS92, 74LS93