SN74HC74DR Detailed explanation of pin function specifications and circuit principle instructions
The component you mentioned, "SN74HC74DR," is part of the Texas Instruments (TI) family of products. It's a dual D-type flip-flop IC in a Surface-Mount Device (SMD) package, specifically in the SOIC-14 (Small Outline Integrated Circuit, 14 pins) package.
1. Pinout and Functions of SN74HC74DR (SOIC-14 Package)
Below is a comprehensive breakdown of the 14 pins, their functions, and usage:
Pin No. Pin Name Function Description 1 Q1 Output Output of the first D-type flip-flop (Q). 2 Q1' Output Inverted output of the first D-type flip-flop (Q'). 3 D1 Input Data input for the first D-type flip-flop. 4 CLK1 Input Clock input for the first D-type flip-flop. 5 CLR1 Input Asynchronous clear input for the first flip-flop. Active low (0). 6 SET1 Input Asynchronous set input for the first flip-flop. Active low (0). 7 GND Ground Ground pin (0V). 8 VCC Power Positive supply voltage (typically +5V or +3.3V). 9 SET2 Input Asynchronous set input for the second flip-flop. Active low (0). 10 CLR2 Input Asynchronous clear input for the second flip-flop. Active low (0). 11 CLK2 Input Clock input for the second D-type flip-flop. 12 D2 Input Data input for the second D-type flip-flop. 13 Q2' Output Inverted output of the second D-type flip-flop (Q2'). 14 Q2 Output Output of the second D-type flip-flop (Q2).2. Pin Function Description
Q1 and Q2 (Pins 1 and 14): These are the outputs of the two D-type flip-flops. These pins output the stored data value when the clock input is triggered. Q1' and Q2' (Pins 2 and 13): These are the inverted outputs of the two flip-flops. They provide the opposite value of Q1 and Q2. D1 and D2 (Pins 3 and 12): These are the data inputs for the first and second flip-flops. The data value is sampled on the rising edge of the clock input and stored in the respective flip-flop. CLK1 and CLK2 (Pins 4 and 11): These are the clock inputs for the first and second flip-flops. When a rising edge is detected on these pins, the data present at the corresponding D inputs is transferred to the outputs (Q1 and Q2). CLR1 and CLR2 (Pins 5 and 10): These are the clear inputs for the flip-flops. When a low signal is applied, the respective flip-flop is asynchronously cleared (output set to 0). SET1 and SET2 (Pins 6 and 9): These are the set inputs for the flip-flops. When a low signal is applied, the respective flip-flop is asynchronously set (output set to 1). GND (Pin 7): This pin connects the ground of the circuit. VCC (Pin 8): This pin connects to the power supply, typically 5V or 3.3V.3. Circuit Principle and Operation
D-type Flip-Flops: The SN74HC74DR consists of two D-type flip-flops. Each flip-flop has a data input (D), a clock input (CLK), a set input (SET), and a clear input (CLR). When the clock (CLK) receives a rising edge, the data (D) input is latched into the flip-flop and can be read on the output (Q). Asynchronous Inputs (CLR and SET): The set (SET) and clear (CLR) inputs are asynchronous, meaning they directly control the output regardless of the clock. A low signal on CLR forces the output to 0, while a low signal on SET forces the output to 1.4. Common FAQs (with detailed answers)
Below are 20 frequently asked questions regarding the SN74HC74DR:
What is the function of the CLK input on the SN74HC74DR? The CLK input controls the timing for data latching into the flip-flop. On a rising edge, the data from the D input is stored into the flip-flop. What is the difference between Q1 and Q1' (Pin 1 and Pin 2)? Q1 is the normal output, while Q1' is the inverted output. Q1' is always the opposite of Q1. How does the CLR pin affect the flip-flop? The CLR input is an asynchronous clear. When a low signal is applied, it forces the Q output to 0, regardless of the clock or data inputs. What happens when the SET pin is activated? When the SET input is low, the flip-flop is asynchronously set, causing the Q output to be 1. Can the SN74HC74DR be used as a memory element? Yes, the SN74HC74DR can be used as a memory element since it stores data on the rising edge of the clock. What are the power supply requirements for SN74HC74DR? The power supply for the SN74HC74DR should typically be 5V, though it can operate with 3.3V as well. What is the purpose of the VCC pin? The VCC pin provides the positive supply voltage to the IC, typically 5V or 3.3V. What happens if the VCC or GND pin is not connected properly? If the VCC or GND pins are not connected correctly, the IC will not function, and outputs may be undefined. Can the SN74HC74DR be used in high-speed circuits? Yes, the SN74HC74DR is capable of high-speed operations and can be used in high-speed digital circuits with clock rates up to tens of MHz. What is the maximum clock frequency for the SN74HC74DR? The maximum clock frequency for the SN74HC74DR is typically specified as around 50 MHz at VCC = 5V. How is the clear (CLR) function used? CLR clears the output of the flip-flop asynchronously when it is low, making the Q output 0. What happens if both CLR and SET are active at the same time? If both CLR and SET are activated simultaneously, the output will be unpredictable. Typically, one should not drive both inputs simultaneously. Can the SN74HC74DR be used in a reset circuit? Yes, the CLR pin can be used to reset the flip-flops, making it suitable for reset circuits. What is the input voltage range for the SN74HC74DR? The input voltage range for the SN74HC74DR is typically 0 to VCC. What is the current consumption of SN74HC74DR? The current consumption depends on the operating conditions but typically ranges from a few mA at 5V. Can the SN74HC74DR be used in low-power applications? Yes, it is a high-speed CMOS device that offers low power consumption when in the inactive state. Is the SN74HC74DR available in different package types? Yes, the SN74HC74 is available in various packages, including SOIC-14, DIP-14, and TSSOP-14. What is the output voltage level for Q and Q' outputs? The output voltage levels for Q and Q' are dependent on the supply voltage (VCC) and the load but typically range between 0 and VCC. Can the SN74HC74DR be used for frequency division? Yes, flip-flops can be used in frequency division circuits, such as counters and dividers. What is the maximum input voltage for the inputs of the SN74HC74DR? The maximum input voltage for the inputs should not exceed VCC by more than 0.5V.This overview provides a comprehensive understanding of the SN74HC74DR, its pinout, usage, and frequently asked questions. The table contains full details of each pin and its function, and the FAQ section provides a deeper understanding of the practical aspects of using the device.