Datasheet
SCLS297D − JANUARY 1996 − REVISED SEPTEMBER 2003
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
n-bit synchronous counters
This application demonstrates how the look-ahead carry circuit can be used to implement a high-speed n-bit
counter. The ’HC161 devices count in binary. Virtually any count mode (modulo-N, N
1
-to-N
2
, N
1
-to-maximum)
can be used with this fast look-ahead circuit.
The application circuit shown in Figure 2 is not valid for clock frequencies above 18 MHz (at 25°C and
4.5-V V
CC
). The reason for this is that there is a glitch that is produced on the second stage’s RCO and every
succeeding stage’s RCO. This glitch is common to all HC vendors that Texas Instruments has evaluated, in
addition to the bipolar equivalents (LS, ALS, AS).