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ULN2003A: PW package thermal performance compare to TBD62003AFWG

Part Number: ULN2003A
Other Parts Discussed in Thread: TPL7407LA

Hello Team,

What is the output on resistance of ULN2003APW? Customer would like to compare its thermal performance to TBD62003AFWG.

Besides, in ULN2003A data sheet, it only states the Maximum Collector Current vs Duty Cycle of D and N package. How about the other 2 packages?

Thanks and best regards,

Victor

  • Hi Victor, 

    You can calculate the on-resistance of the ULN2003APW by taking Vce / Ic in the datasheet. At higher voltages, it's easier to take your load resistance and find the current passing through each channel (Ice). After this, you can calculate the power dissipation using the following equation: 

    1:  l:   Pd = Ice ^2 * Rds   (Per Channel)

    2: Add the power dissipations together from all active channels

    3: Multiply Pd * ThetaJA + Tambient to find the junction temperature of the device.

    If the value exceeds the 125C, then the device cannot support the load current you are supplying.

    Thanks,

    Arthur Huang

  • Hi Arthur,

    Thanks for your reply.

    However, there is no Vce at Ic=500mA value in data sheet. Below is customer's test data. 

    Under this test condition, the Rdson of ULN2003A is about 1.06Ohm which is way smaller than Rdson at 350mA loading(~3.4Ohm) in data sheet.

    Do you have a newer version data sheet or test data showing the Rdson of ULN2003A?

    Thanks and best regards,

    Victor

  • Hi Victor,

    Can you comment on how the customer is measuring the voltage drop? What is your input supply voltage? Are they measuring the RDSon by:

    (input voltage - output voltage) / Iload

    If you look at Figure 1 in the ULN2003A datasheet, you can see the relationship between VCE and ICE. At 500ma ICE,  the VCE will be between 1.5V and 1.7V, depending on the input current from the ON/B pin.

    Thanks,

    Arthur Huang

  • Hi Arthur,

    The base input voltage is 5V and voltage at load is 12V. They take (voltage across load resistor@0mA - voltage across load resistor@500mA) / Iload as the equivalent on resistance. Actually (voltage across load resistor@0mA - voltage across load resistor@500mA) is same as Vce as the transistor/mosfet is in series with the load.

    Do you think the difference between ULN2003 and TBD62003 may come from that ULN2003 is transistor array while TBD62003 is MOSFET array?

    Thanks and best regards,
    Victor
  • Hi Victor,

    Yes, that could account for the difference between the ULN2003 and the TBD62003. If you're looking for a MOSFET array equivalent, I suggest looking at the TPL7407LA. Although the device can't go up to 50V, it provides better Ron and performance capabilities.

    Thanks,

    Arthur Huang
  • Hi Arthur,

    Thanks for the suggestion. I guess my customer might swap the test result.

    Just want to confirm that for ULN2003, the Vce should be higher than 1.3V as there are 2 transistors and each Vce is ~0.65V while the MOSFET array should have lower on resistance(well, at least from both MOSFET array data sheet it shows so).

    Thanks and best regards,

    Victor

  • Hi Victor, 

    The max VCE will be less than 1.2V, typically around 0.9V. The current does not pass through the left BJT, this is use to bias the main pass FET correctly. Regarding a comparison vs the TPL7407LA and other MOSFET arrays, the TPL7407LA will dissipate less power and draw less current on the input.

    Thanks,

    Arthur Huang