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Product details

Parameters

Function Counter Bits (#) 4 Technology Family ALS VCC (Min) (V) 4.5 VCC (Max) (V) 5.5 Input type TTL Output type CMOS open-in-new Find other Counter, arithmetic & parity function ICs

Package | Pins | Size

PDIP (N) 16 181 mm² 19.3 x 9.4 SOIC (D) 16 59 mm² 9.9 x 6 open-in-new Find other Counter, arithmetic & parity function ICs

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
  • Package Options Include Plastic Small-Outline (D) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (N) and Ceramic (J) 300-mil DIPs
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Description

The 'ALS191A are synchronous 4-bit reversible up/down binary counters. Synchronous counting operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincidentally with each other when instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters.

The outputs of the four flip-flops are triggered on a low-to-high-level transition of the clock (CLK) input if the count enable () input is low. A high at inhibits counting. The direction 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, the counter counts down.

These counters feature a fully independent clock circuit. Changes at the control inputs ( and D/U\) that modify the operating mode have no effect on the contents of the counter until clocking occurs. The function of the counter is dictated solely by the conditions meeting the stable setup and hold times.

These counters are fully programmable. Each output can be preset to either level by placing a low on the input and entering the desired data at the data inputs. The output changes to agree with the data inputs independently of the level of the clock input. This feature allows the counters to be used as modulo-N dividers by simply modifying the count length with the preset inputs.

CLK, D/U\, and are buffered to lower the drive requirement, which significantly reduces the loading on (current required by) clock drivers, for long parallel words.

Two outputs are available to perform the cascading function: ripple clock and maximum/minimum count. The latter output produces a high-level output pulse with a duration approximately equal to one complete cycle of the clock while the count is minimum (0) counting down or maximum (15) counting up. The ripple-clock output () produces a low-level output pulse under those same conditions, but only while the clock input is low. The counter easily can be cascaded by feeding the ripple-clock output to the enable input of the succeeding counter if parallel clocking is used, or to the clock input if parallel enabling is used. The maximum/minimum count (MAX/MIN) output can be used to accomplish look ahead for high-speed operation.

The SN54ALS191A is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALS191A is characterized for operation from 0°C to 70°C.

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Technical documentation

= Top documentation for this product selected by TI
No results found. Please clear your search and try again. View all 12
Type Title Date
* Datasheet Synchronous 4-Bit Up/Down Binary Counters datasheet (Rev. C) Jul. 01, 1996
Selection guide Logic Guide (Rev. AB) Jun. 12, 2017
Application note Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) Dec. 02, 2015
User guide LOGIC Pocket Data Book (Rev. B) Jan. 16, 2007
Application note Semiconductor Packing Material Electrostatic Discharge (ESD) Protection Jul. 08, 2004
More literature Logic Cross-Reference (Rev. A) Oct. 07, 2003
Application note TI IBIS File Creation, Validation, and Distribution Processes Aug. 29, 2002
Application note Bus-Interface Devices With Output-Damping Resistors Or Reduced-Drive Outputs (Rev. A) Aug. 01, 1997
Application note Designing With Logic (Rev. C) Jun. 01, 1997
Application note Input and Output Characteristics of Digital Integrated Circuits Oct. 01, 1996
Application note Live Insertion Oct. 01, 1996
Application note Advanced Schottky (ALS and AS) Logic Families Aug. 01, 1995

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Hardware development

EVALUATION BOARD Download
10
Description
This EVM is designed to support any logic device that has a D, DW, DB, NS, PW, P, N, or DGV package in a 14 to 24 pin count.
Features
  • Board design allows for versatility in evaluation
  • Supports a wide-range of logic devices

CAD/CAE symbols

Package Pins Download
PDIP (N) 16 View options
SOIC (D) 16 View options

Ordering & quality

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