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TPS4H000-Q1: Operation queries

Part Number: TPS4H000-Q1

Hi,

Kindly support for below queries regarding TPS4H000AQPWPRQ1.

  1. Can we make all 04 output channels ON simultaneously with 0.5Amp normal DC load current each channel ? i.e. total Normal DC load current through High Side

              switch will be 2Amp ( 4 x 0.5A).

2.Output channels pins are ESD protected or not?  ( for Contact Discharge@ +/-4KV & Air discharge@ +/-8KV).   If not, what are TI recommendation to protect device from ESD ?

3.We will not use any diagnostic status pin/feature. In this case, for Short to GND and Overload fault condition, device will  go in thermal shutdown mode & becomes OFF. When we remove fault condition i.e.        overload or short to GND condition, then device automatically recovers. Is it OK?

4.We will not use any diagnostic status pin/feature. In this case,  how Open-load Detection feature used ?

5.There will be isolation between Digital -Microcontroller section and High Side Switch section. In this case there should be two separate individual 5V DC Supplies, one for Microcontroller section & second       for High Side switch section. For this we have to use one additional “24V to 5V DC-DC converter power supply” for High Side switch section ( i.e. INx, STx, pins etc..). For this, is there any alternative low cost solution?

Kindly provide feedback ASAP.

  • Hi Yash,

    Thanks for the question.

    1. What will the ambient temperature be? the quick way to determine if the device will be at an acceptable temperature is multiply the power by the junction to ambient thermal resistance. This will tell you how much the temperature will rise above the ambient temperature.  Determine the power using I*I*Ron_max, then multiply the total power (all 4 channels) by the Junction-to-ambient thermal resistance in section 7.4. Add the system ambient temperature to this value to get the expected temperature rise within the device. if it's above 150C then we wouldn't recommend this device for the application.

    2. We've tested similar IP up to +-8kV for contact discharge using ISO 10605. The device passed under these test conditions. We do recommend 22nF capacitors for ESD protection.

    3.Yes, this is the expected performance of the device.

    4. If you are not using any of the diagnostic or status pins, there is no way to notify the system that there is an open load. That is the tradeoff.

    5. I would check into the isolation E2E forum. To my knowledge there is no alternative solution for this.

  • Hi,

    Kindly support on below queries.

    1) In Datasheet it is mentioned as Internal current limit (ICL) is 1 to 1.6A, please clarify that this internal current limit is per channel or sum of all output current ?
    2) If we have to apply external current limit, what is the maximum current limit specified by TI ? (Also, please clarify, current limit is per channel or sum of all output current ?)
    3) Our maximum ambient temperature is 60deg. Cel., then what is maximum current (sum of all channels) suggested for our application ?

    Rgds,
    Yash
  • Yash,

    1) This is per channel.
    2+3) When driving higher current loads, the thermal capabilities of the device will be the limiting factor. The quick method of determining this is to make sure the junction temperature stays below 150C. With an ambient temperature of 60C, the power through the chip should not cause the device to reach 150C (90C rise from ambient). Using the device thermal resistance - junction to ambient (datasheet section 7.4) of 38.5, we can calculate that the power dissipation should be below 2.3W (90/38.5 = ~2.3). For power, we use I*I*Ron_max. Max Ron is used because the device will heat up, raising the Ron value. For the TPS4H000, the max Ron is 2ohms, so you would want to drive 1A max through the device under this scenario. If you need to drive a higher load, I would suggest the TPS4H160.

    (rounding was used to simplify the explanation)
  • Hi,

    Can we drive 1A load per channel or sum of 4 channel?
  • Hi Yash,

    The recommended maximum current per channel is 0.75A, so to pass 1A through the device, you would need to put at least two channels in parallel. However, keep in mind that the amount of power dissipation in the device would limit your ambient temperature to about 70C since the junction temperature should not exceed 150C. 

    Thanks,

    Alek Kaknevicius