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LAUNCHXL-F280039C: Shorting pins at the MCU.

Yash Bijawat
Prodigy 20 points

Part Number: LAUNCHXL-F280039C
Other Parts Discussed in Thread: TMS320F280039C

I am using this development kit LAUNCHXL-F280039C in my setup. It is been observed that pin number 37 at the MCU is not connected to any header pins so I can't provide any voltage to pin 37. So what I did is that I short pin 37 to 35 at MCU as pin 35 is connected to header pin, so by controlling pin 35 I will be able to control pin 37 also. Note: Configuration of both the pins are same, both are analog input.

Will it cause any problem to the MCU or to the development kit.

  • 0
    TI__Expert 6670 points

    Hello,

    Shorting pin 37 to pin 35 on the TMS320F280039C is not recommended and could cause problems, even though both are configured as analog inputs.

    Charge-sharing between sample-and-hold capacitors: Each ADC input pin has its own internal sample-and-hold capacitor and switching circuitry. When you short two pins together, their capacitors interact unpredictably during sampling windows. The input driver circuit must charge each sample-and-hold capacitor to the expected level within its acquisition window — shorting pins together can violate this requirement and cause measurement errors or instability.

    Internal architecture conflicts: The F28003x analog pins include a 53Ω series switch creating an isolated node shared between the ADC and CMPSS comparator. Shorting two such pins together create an unintended shared node that can be disturbed when either ADC channel samples, potentially causing false events or corrupted readings.

    Electrical specification violations: Analog pins have specified leakage of 0.1 µA max, and the internal circuitry is designed for independent operation. Forcing two channels to the same node can create current injection scenarios that exceed safe operating limits.

    Is there any specific reason you have to use ADC A8?