74LS90D中文资料安森美半导体数据手册PDF规格书

The SN54 / 74LS90, SN54 / 74LS92 and SN54 / 74LS93 are high-speed 4-bit ripple type counters partitioned into two sections. Each counter has a divide-by-two section and either a divide-by-five (LS90), divide-by-six (LS92) or divide-by-eight (LS93) section which are triggered by a HIGH-to-LOW transition on the clock inputs. Each section can be used separately or tied together (Q to CP) to form BCD, bi-quinary, modulo-12, or modulo-16 counters. All of the counters have a 2-input gated Master Reset (Clear), and the LS90 also has a 2-input gated Master Set (Preset 9).

• Low Power Consumption . . . Typically 45 mW

• High Count Rates . . . Typically 42 MHz

• Choice of Counting Modes . . . BCD, Bi-Quinary, Divide-by-Twelve, Binary

• Input Clamp Diodes Limit High Speed Termination Effects