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TPS27S100: Finding right component to control 12V 30Watt heater

Amir Eshraghi
Expert 1270 points
Part Number: TPS27S100

Hi

I want to know if TPS27S100 is good part to control 30W 12V heater, using microcontroller pwm.

Thank you

  • 0
    TI__Mastermind 32650 points

    Hi Amir,

    Due to the timing limitations of the device, a fast PWM will not work with this device. I think the maximum frequency would be around 1kHz to make actual changes with duty cycle. 

    As far as loading goes, 12V, 30W heater means its maximum current draw is 2.5A. TPS27S100 is rated up to 4A nominal so I believe it will work.

  • 0 in reply to Shreyas Dmello
    Expert 1270 points

    HI Shreyas,

    We can run PWM from 122Hz to 32Khz. Also this device will be super hot since Thermal junction Ambient  is 41 C/W or  RθJC 31, how will I run that since I am running 30W. (30*41 = 1230C)

    Do you have any other  p/n or suggestion we can use for running heater.  

    Thank you

  • 0 in reply to Amir Eshraghi
    TI__Mastermind 32650 points

    Hi Amir,

    Please keep the PWM lower than 1kHz. If you can run it slower, that will be preferred. Any PWM faster than this will cause the device to not respond correctly to the inputs. I would suggest 200Hz.

    Also the load power is 30W. This does not mean that 30W will be dropped across the FET. the power dissipated in steady state is I^2*R_on of the device.

    This means that power dissipated across the FET is 2.5*2.5*0.166 at the worst case(166mOhm at 150C from the datasheet). The power is only 1.0375 W.

    This power increases the junction temperature by a max by 44.2C assuming you are using the QFN package and are cooling with ambient(R_theta,j,a). The resulting junction temp would be 86.2C.

    While this is hot, this is well within the operating range of this device and any sort of cooling or thermal relief will only help it further.