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High-Side load switch

Gilad Friefeld
Intellectual 330 points
Other Parts Discussed in Thread: TPS1H100-Q1, TPS1HC100-Q1

Hi.

I'm looking for a High-Side load switch  that can handle current pulses (Load = PWM high power LED driving up to 2A max).

12V IN, 2A max PWM pulses. PGOOD/FLT signal, EN input, soft start (optional), programable current limit (via external resistor), output current measurement (optional via internal ADC). 

Please advise, 

Thanks.  

  • 0
    TI__Mastermind 32650 points

    Hi Gilad,

    I would recommend taking a look at the High Side Switch devices like TPS1HC100-Q1 and TPS1H100-Q1. The limit for PWM frequency is 2kHz but these devices can support 2A at 12V with programmable current limit. They do offer a current sense/measurement through an internal current mirror so an external MCU or ADC must be used.

    Thanks,

    Shreyas

  • 0 in reply to Shreyas Dmello
    Intellectual 330 points

    Hi Shreyas, 

    Thanks for the quick and informative response. 

    Just to clarify the requirements compliance, PWM frequency is normally 60/120Hz (LED Blinking). Pulse Duty Cycle  is very short, around 10uSec. 

    Please approve that the TPS1H100-Q1 can handle such a load without triggering the current limit protection (assuming 12V@2A max). 

    Thanks again. 

  • 0 in reply to Gilad Friefeld
    TI__Mastermind 32650 points

    Hi Gilad,

    60/120Hz is acceptable but the small duty cycle is not. The turn on delay time for TPS1H100 ranges from 20us to 50us and so any shorter duties are not supported.

    Current limit is not a concern as the device CL can be adjusted to higher values. For faster PWM with such short duties, our High Side Switches will not work.

    Thanks,

    Shreyas

  • 0 in reply to Shreyas Dmello
    Intellectual 330 points

    Hi Shreyas. 

    Thanks again.

    Looking over TPS1H100 datasheet, page 9 Figure 5. Switching Characteristics Diagram; as I understand this:
    If the sTPS1H100 VIN is turned ON and OFF, than VOUT Turn-on delay time is between 20us to 50us.
    However, our application is used to source 12V to a PWM driver (Load) that blinks a high power LED at short duty-cycles, meaning that the TPS1H100 12V IN stays ON and enabled as long as we supply 12V to the PWM driver. Are we still bound to the same limitations? we are not switching the TPS1H100 ON/OFF or using it as a PWM driver, the LOAD is responsible to do so, we just have to keep sourcing 12V without shutting down the TPS1H100.

    Sorry if my explanation is not clear, and please feel free to correct me if I'm wrong. 

    Thanks. 

  • 0 in reply to Gilad Friefeld
    TI__Mastermind 32650 points

    Hi Gilad,

    Let me confirm the setup. You are not PWM'ing the high side switch with the IN pin, but rather you are just using the high side switch to supply 12V to a PWM driver which then PWM's the LED. The high side switch is always ON.

    Essentially the setup is as follows:

    12V source -> High Side Switch -> LED Driver Load -> LED -> GND

    In this situation, there is no concern for delay timing. This solution is acceptable for the switch and the 2A limit is not a concern. The switch has adjustable current limit and is rated for a DC current of 4A. I also believe that TPS1HC100-Q1 will work here. Do note that with such short pulses of current, the concern now becomes if there is enough time for the current sense pin to respond to the pulse. This is not a concern that will damage the device but a novel sensing solution may need to be used if it is too fast for the high side switch. All protections will work as normal.

    Thanks,

    Shreyas

  • 0 in reply to Shreyas Dmello
    Intellectual 330 points

    Hi.

    setup is confirmed. Can you please explain regarding “novel sensing solution”? What is the valid technical solution for this setup and would you recommend any other high side solution? 
    Thanks. 

  • +1 in reply to Gilad Friefeld
    TI__Mastermind 32650 points

    Hi Gilad,

    If the internal current sensing is too slow for the solution, I would recommend looking at some discrete current sensing devices like current sense amplifiers. I cannot comment on which one will work best for you but this is only if the internal sensing solution is not fast enough to respond to the small duty.

    Thanks,

    Shreyas