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SN74LVCC4245A: SN74LVCC4245

AREZKI ALI-BACHA
Prodigy 30 points
Part Number: SN74LVCC4245A

Hello,

Were are investigating a board returned for logic failure.

We would like to know if an overcurrent protection exists on the component 74LVCC4245.

 

We did tests on our board equipped with the component.

Configuration: VCCA = 5V VCCB = 3.3V

Direction set from B to A

3.3V applied on B2 so A2 is driven high to 5V

Test: We applied a short circuit on A2 output.

Results :

The VCCA still around 5V

Io on A2 was measured at 300mA few seconds before a continuous 290mA.

Vo on A2 was measured around 155mV Test: 3.3V applied on B2 so A2 is driven high to 5V

Results :

Vo on A2 was measured around 5V. OK

Visual inspection: No dammage on the component.

What do you think about this behaviour ?

  • 0
    Guru 280010 points

    TI says:

    This device includes balanced CMOS push-pull outputs. The term "balanced" indicates that the device can sink and source similar currents. The drive capability of this device may create fast edges into light loads so routing and load conditions should be considered to prevent ringing. Additionally, the outputs of this device are capable of driving larger currents than the device can sustain without being damaged. It is important for the output power of the device to be limited to avoid damage due to overcurrent. The electrical and thermal limits defined in the Absolute Maximum Ratings must be followed at all times.

    The absolute maximum rating for the output current is 50 mA per pin (100 mA total). Your test might have damaged or degraded the device.

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Hello,

    Actually we would like to know is if the 300mA current can explained by the push-pull output circuit (Rdon for example)

    We agree that the maximum current is overpassed when we applied a short on the ouput.

    We are not in a normal case but in a failure mode study.

    BR

  • +1 in reply to AREZKI ALI-BACHA
    TI__Mastermind 44665 points

    Hi Arezki,

    This device has stronger output drivers. Shorting the output to GND in a High state will effectively put 5 V across the pFET. You can use Ohms law to determine the Rdson of that pFET which will be in the realm of 15-20 ohms.