BCD-to-seven-segment driver 7447 features and I/O polarity: Evaluate the statement: “The 7447 IC accepts a 4-bit BCD input, provides seven individual active-LOW segment outputs for driving a common-anode display, and includes ripple blanking input (RBI) and ripple blanking output (RBO) pins.”

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
The 7447 is a classic BCD-to-seven-segment decoder/driver used in introductory digital electronics. Understanding its input coding, output polarity, and auxiliary control pins is essential when interfacing counters or microcontrollers to seven-segment LED displays, particularly common-anode modules that expect active-LOW segment drive signals.


Given Data / Assumptions:

  • Target device: 7447 BCD-to-seven-segment decoder/driver.
  • Inputs: four-bit BCD representing decimal 0–9.
  • Outputs: seven lines intended to drive segments a–g.
  • Control pins: ripple blanking input (RBI) and ripple blanking output (RBO) for multi-digit leading-zero suppression.


Concept / Approach:
The 7447 translates a BCD nibble into the appropriate segment pattern. Its outputs are active-LOW, meaning a logic 0 turns a segment on when used with a common-anode display. RBI/RBO allow cascaded blanking to automatically suppress leading zeros across multiple digits, improving readability without extra logic.


Step-by-Step Solution:

Identify the I/O convention: BCD in (4 bits) → seven active-LOW outputs.Confirm display compatibility: active-LOW suits common-anode LED modules.Note auxiliary features: RBI accepts blanking from a more-significant digit; RBO forwards blanking to the next digit.Conclude the stated feature set matches the 7447 device.


Verification / Alternative check:
Examine a typical 7447 truth table and pinout: outputs labeled a–g are open-collector, active-LOW; RBI/RBO pins are present for ripple blanking chains. Laboratory tests with a counter feeding the 7447 confirm correct segment patterns and blanking behavior.


Why Other Options Are Wrong:

  • Incorrect: Conflicts with the standard 7447 functionality.
  • Only true for the 7448 variant: 7448 is for common-cathode (active-HIGH), not the 7447.
  • Depends on supply voltage: Polarity and features do not change with typical Vcc.
  • Applies only to LCD drivers: 7447 is an LED display driver/decoder.


Common Pitfalls:
Confusing 7447 (active-LOW) with 7448 (active-HIGH); omitting required segment current limiting; forgetting that open-collector outputs may require pull-ups depending on wiring.


Final Answer:
Correct

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