74192 Technical Summary

74192 Synchronous 4-Bit Up/Down Counter Technical Summary

Overview

The 74192 is a synchronous, presettable 4-bit up/down counter featuring separate clock inputs for counting up and down. This high-speed TTL integrated circuit is designed for applications requiring precise counting sequences with the flexibility of parallel loading. The device operates in either count-up or count-down mode based on the selected clock input, with carry and borrow outputs facilitating cascading for higher-bit counters.

Key operational characteristics include synchronous counting (all flip-flops change state simultaneously), asynchronous parallel loading, and clear functionality. The 74192 is part of the 7400 series of logic devices and is widely used in digital systems where reliable counting operations are required.

Features

Synchronous Operation: All state changes occur simultaneously with the clock pulse
Dual Clock Inputs: Separate clock inputs for up (CPU) and down (CPD) counting
Asynchronous Parallel Load: Data can be loaded independently of clock status
Asynchronous Master Reset: Clears all flip-flops regardless of clock state
Cascading Capability: Carry (TCU) and Borrow (TCD) outputs enable easy expansion
High-Speed Operation: Typical propagation delay of 15ns
Wide Operating Voltage: 4.75V to 5.25V
TTL-Compatible Inputs and Outputs: Standard logic levels for easy integration
Available in Multiple Packages: PDIP, CDIP, SOIC, and other industry-standard formats

Applications

The 74192 finds use in numerous digital counting applications including:

Digital frequency counters and timers
Industrial control systems
Event counting and sequencing
Digital clocks and timekeeping circuits
Position and rotation counting
Inventory tracking systems
Programmable logic controllers
Test and measurement equipment
Educational demonstration circuits

Electrical Characteristics

Absolute Maximum Ratings

Supply Voltage (Vcc): 7V
Input Voltage: 5.5V
Operating Temperature Range: 0°C to +70°C (Commercial)
Storage Temperature Range: -65°C to +150°C

Recommended Operating Conditions

Supply Voltage (Vcc): 4.75V to 5.25V
High-Level Input Voltage: 2V min
Low-Level Input Voltage: 0.8V max
Input Rise/Fall Time: 20ns max

DC Characteristics

High-Level Output Voltage: 2.4V min (Ioh = -400μA)
Low-Level Output Voltage: 0.4V max (Iol = 16mA)
Input Clamp Voltage: -1.5V max (Iik = -18mA)
Power Supply Current: 34mA max (all outputs high)

AC Characteristics (Vcc = 5V, TA = 25°C)

Maximum Clock Frequency: 32MHz typical
Propagation Delay (Clock to Output): 15ns typical
Propagation Delay (Parallel Load to Output): 20ns typical
Propagation Delay (Reset to Output): 25ns typical
Carry/Borrow Delay: 15ns typical

Functional Description

The 74192 operates as a synchronous 4-bit counter with several control inputs that determine its mode of operation:

Counting Operation

When the parallel load input (PL) is high and the clear input (MR) is low, the counter will increment on the rising edge of the CPU input (while CPD is high) or decrement on the rising edge of the CPD input (while CPU is high). The direction of counting is determined by which clock input receives pulses.

Parallel Loading

A low level on the PL input loads the data present at the parallel inputs (P0-P3) into the counter asynchronously, regardless of the clock states. This allows presetting the counter to any desired value.

Clearing

A high level on the MR input asynchronously clears all flip-flop outputs (Q0-Q3) to low, overriding all other inputs.

Cascading

The carry output (TCU) goes low when counting up and the counter reaches its maximum count (1111). The borrow output (TCD) goes low when counting down and the counter reaches its minimum count (0000). These outputs facilitate cascading multiple counters for higher counting ranges.