Problem 2
Wire TF-BUF5 from its card: power, enable, input, a 1 kΩ LED, and 100 nF.
- Wire the pins the card names. EN_N is not the supply.
- 100 nF on the supply and 1 kΩ in the LED path are separate requirements.
Context
This buffer is not a generic box. Its card names power, ground, an active-low enable, and the signal pins. A capacitor value is part of the circuit. You used a resistor value in the LED problem; here the card tells you which value belongs on which pin.
Components on this challenge
- TF-BUF5. A training buffer. Power, ground, an active-low enable, and an output are different pins.
- Capacitor. Stores charge and supplies a short pulse of current. With a resistor it also sets a time.
- Resistor. Limits current. The voltage across it divided by its resistance is the current through it.
- LED. A diode that emits light when current flows from anode to cathode.
Full brief
Wire the buffer from its device card: power, ground, the active-low enable, the input, the LED path, and the supply capacitor. The truth test watches the output pin.
How PCBGrade measures this
TF-BUF5 is a fictional buffer. J1 pin 1 is 3V3, pin 2 is IN, and pin 3 is GND. Tie VCC to 3V3, GND and EN_N to GND, and IN to J1 pin 2. OUT goes through 1 kΩ to the LED anode; the LED cathode goes to GND. J2 pin 1 is on OUT and pin 2 is on GND. Put 100 nF between 3V3 and GND. The truth test watches OUT, not the LED: both IN = 0 and IN = 1 must match, and only when the part is powered with EN_N low. Disabled is Z and unpowered, floating, or conflicting drive is X; neither counts as 0. Points: each of VCC, GND, EN_N, IN, and OUT is 8. The 1 kΩ value is 10, the series path is 10, the LED cathode is 5, and J2 is 5. The capacitor is 15. The truth test is 15. A wrong resistor still passes. An unpowered part, EN_N not low, a floating required pin, or a driver conflict caps the score at 60. A missing capacitor does not.
- datasheet/pin interpretation and required pin usage · 40 pts
- connectivity · 30 pts
- decoupling component/value · 15 pts
- functional truth test · 15 pts
- Cap 60: An unpowered buffer, EN_N not held low, a floating required pin, or a driver conflict caps the score at 60.
Reference
TF-BUF5
Single buffer. OUT follows IN only when VCC is powered and EN_N is low.
- 1. IN. Input
- 2. GND. Ground
- 3. EN_N. Active-low enable
- 4. OUT. Output
- 5. VCC. Supply