74ls90 pdf

DM74LS90/DM74LS93
Decade and Binary Counters
General Description
Each of these monolithic counters contains four masterslave
flip-flops and additional gating to provide a divide-bytwo
counter and a three-stage binary counter for which the
count cycle length is divide-by-five for the 'LS90 and divideby-
eight for the 'LS93.
All of these counters have a gated zero reset and the LS90
also has gated set-to-nine inputs for use in BCD nine's complement
applications.
To use their maximum count length (decade or four bit binary),
the B input is connected to the QA output. The input
count pulses are applied to input A and the outputs are as
described in the appropriate truth table. A symmetrical divide-
by-ten count can be obtained from the 'LS90 counters
by connecting the QD output to the A input and applying the
input count to the B input which gives a divide-by-ten square
wave at output QA.
Features
Y Typical power dissipation 45 mW
Y Count frequency 42 MHz