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PCA9306: Need Recommended Operating Junction Temperature Limit

Dave Womac
Prodigy 80 points
Part Number: PCA9306

  1. PCA9306DCUT

    • What is the recommended operating Tj (Junction Temperature)?

      1. Part is rated for -40 °C to +85 °C ambient operation

      2. A rated power dissipation is not provided in the datasheet, so I am not able infer an operating Tj limit from the TheatJA of 210.1 °C/W at Ta = 85 °C
        Can you provide the rated power dissipation?

      3. Our usage condition results in Tj = 117 °C

      4. Can I run this part at Tj = 117 °C and be assured of full functionality?

        • If not, do you offer a part that will provide this functionality with a higher Recommended Operating Junction Temperature?

  • 0
    TI__Guru 73871 points
    Hey Dave,

    "Can you provide the rated power dissipation?"
    The power dissipation of this device should expected to be incredibly low as the pass FET RDs(on) in normal conditions is around 3 to 5 ohms. At an ambient temperature I would guess the Rds(on) would be around 8 ohms. Max power dissipation can be estimated at 128mA x 7V = 896mW. This is a really extreme worst case scenario as in normal operating conditions the current flowing through this device will be MUCH lower.

    "Can I run this part at Tj = 117 °C and be assured of full functionality?"
    The absolute maximum junction temperature this device can take is 125C so this device will function at 117C but keep in mind the device may not meet datasheet specs at this kind of temperature (mainly the prop delays will be a little bit longer likely in the low ns range). This is due to the Rds(on) becoming larger with higher temperature.

    "If not, do you offer a part that will provide this functionality with a higher Recommended Operating Junction Temperature?"
    We do have the PCA9306TDCURQ1 which supports a max operating temperature of 105C so this would be better suited than the catalogue version.

    I did some testing with this device drawing around 6mA of current at 3.3V on Vref2 and found at 105C the Rds(on) was about 6 ohms. At 117C I expect the Rds(on) to go up by 1 or 2 ohms.

    -Bobby
  • 0 in reply to BOBBY
    Prodigy 80 points

    Thank you.

    Can you tell me what the Recommended Operating Junction Temperature limit is for PCA9306TDCUT. Absolute Max Rating is 125C, but that is just a damage limit, not a functional limit, per note (1) in Absolute Maximum Ratings, see datasheet excerpt below.

    I need to know up to what junction temperature functional operatoin is assured.

    Similarly, can you tell me what the Recommended Operating Junction Temperature limit is for the Ta = 105C  rated part you recommended, PCA9306TDCURQ1 ?

    Excerpt from PCA9306DCUT datasheet:

  • 0 in reply to Dave Womac
    TI__Guru 73871 points

    Hello Dave,

    "Can you tell me what the Recommended Operating Junction Temperature limit is for PCA9306TDCUT."

    -I assume you are actually asking about PCA9306DCUT as the catalogue part does not have a version with "T" between the 6 and the D. If this is the case then the recommended junction temperature is also 85C.

    "I need to know up to what junction temperature functional operatoin is assured."

    -The device will function and work above of the recommended operating range but when you are outside this range you may find the device will not meet datasheet specs. (this is what I was referring to in my last post when I was discussing Rds(on) and prop delays). The device will still function below 125C. This means from -40C to just below 125C the device is expected to function. (Once again, when you are outside recommended temperature but below absolute maximum temperature then the device should still function but may not meet datasheet specs)

    "Similarly, can you tell me what the Recommended Operating Junction Temperature limit is for the Ta = 105C  rated part you recommended, PCA9306TDCURQ1 ?"

    -The recommended operating junction temperature is the same at 105C.

    -Bobby