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TPS274C65CP: Inquiry Regarding TPS274C65CP Application in PWM-Controlled Heating System

wjhsu
Prodigy 45 points
Part Number: TPS274C65CP

Tool/software:

Hi,

I'm currently designing a multi-channel heating system, with each heating element specified at DC24V/16W. The system will use PWM control with a frequency expected to be between 20KHz and 50KHz (still undecided).

Initially, I planned to use configuration B (as shown in the attached diagram) to control the heating elements, thereby utilizing the current limiting and protection mechanisms of the TPS274C65CP to detect any abnormalities in the heating elements. Later, upon reviewing Figure 9-2 in section 9.2.3 Application Curves of the datasheet, it seems that configuration A might achieve PWM control, allowing us to eliminate the need for additional MOSFETs and thereby simplify the heating element control circuitry of the entire system.

My questions are:

  1. Is it reasonable to use configuration A or configuration B to apply the TPS274C65CP in a PWM-controlled heating element circuit?
  2. If configuration B can be reasonably applied to PWM control, will the protection mechanisms of the TPS274C65CP still function correctly? Specifically, since the PWM signal is connected to the EN pin of the TPS274C65CP, will it still be able to detect if the heating element is disconnected (open load) when EN = Low?

Thank you for your assistance.

Best regards,

  • +1
    TI__Mastermind 28490 points

    Hi wjhsu,

    Because of the turnon/turnoff times and Ton/Toff mismatch of the TPS274C65CP, it's recommended to keep the maximum PWM frequency to 1kHz. Thus, Configuration B is recommended.

    In Configuration B, the PWM signal should be applied to the load side MOSFETs. This device only has open-load/wire-break detection when the EN pin is low, so it will not signal an open load fault when the EN pin is high. However, it will protect against overcurrent when EN is high.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Prodigy 45 points

    Hi Patrick,

    Thank you for your response.

    I noticed the maximum PWM frequency is specified as 1KHz, but I am confused because Figure 9-2 in the TPS274C65CP datasheet shows waveforms for a load switching with a 250KHz PWM signal. Could you please help clarify this for me?

    Thank you,

    Best regards,

  • +1 in reply to wjhsu
    TI__Mastermind 28490 points

    Hi wjhsu,

    Yes, that is a typo - the figure should read 250Hz. The time divisions in that figure are 4ms.

    Thanks,

    Patrick