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Standard Products

UT54ACS191/UT54ACTS191

Synchronous 4-Bit Up-Down Binary Counters

Datasheet

November 2010

www.aeroflex.com/logic

FEATURES

Single down/up count control line

Look-ahead circuitry enhances speed of cascaded counters

Fully synchronous in count modes

Asynchronously presettable with load control

1.2μ CMOS

- Latchup immune

High speed

Low power consumption

Single 5 volt supply

Available QML Q or V processes

Flexible package

- 16-pin DIP

- 16-lead flatpack

UT54ACS191 - SMD 5962-96564

UT54ACTS191 - SMD 5962-96565

DESCRIPTION

The UT54ACS191 and the UT54ACTS191 are synchronous 4-

bit reversible up-down binary counters. Synchronous counting

operation is provided by having all flip-flops clocked simulta-

neously so that the outputs change coincident with each other

when so instructed. Synchronous operation eliminates the out-

put counting spikes associated with asynchronous counters.

The outputs of the four flip-flops are triggered on a low-to-high-

level transition of the clock input if the enable input (CTEN) is

low. A logic one applied to CTEN inhibits counting. The di-

rection of the count is determined by the level of the down/up

(D/U) input. When D/U is low, the counter counts up and when

D/U is high, it counts down.

The counters feature a fully independent clock circuit. Changes

at control inputs (CTEN and D/U) that will modify the operating

mode have no effect on the contents of the counter until clocking

occurs.

The counters are fully programmable. The outputs may be

preset to either logic level by placing a low on the load input

and entering the desired data at the data inputs. The output will

change to agree with the data inputs independently of the level

of the clock input. The asynchronous load allows counters to

be used as modulo-N dividers by simply modifying the count

length with the preset inputs.

Two outputs have been made available to perform the cascading

function: ripple clock and maximum/minimum (MAX/MIN)

count. The MAX/MIN output produces a high-level output

pulse with a duration approximately equal to one complete cycle

of the clock while the count is zero (all outputs low) counting

down or maximum (15) counting up.

PINOUTS

16-Pin DIP

Top View

16-Lead Flatpack

Top View

The ripple clock output (RCO) produces a low-level output pulse

under those same conditions but only while the clock input is

low. The counters easily cascade by feeding the RCO to the

enable input of the succeeding counter if parallel clocking is

used, or to the clock input if parallel enabling is used. Use the

MAX/MIN count output to accomplish look-ahead for high-

speed operation.

The devices are characterized over full military temperature

range of -55

°C to +125°C.

1

2

3

4

5

7

6

16

15

14

13

12

10

11

B

CTEN

D/U

A

CLK

RCO

MAX/MIN

C

8

9

D

LOAD

1

2

3

4

5

7

6

16

15

14

13

12

10

11

89

B

CTEN

D/U

A

CLK

RCO

MAX/MIN

LOAD

C

D