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LM5150-Q1: Standby and Status-off threshold definition

Webber Chen
Prodigy 30 points
Part Number: LM5150-Q1
Other Parts Discussed in Thread: LM5155-Q1

Hi Sir

I want to use LM5150-Q1 in T-Box system design and I find there are two configuration(SS and EC) in IC. But i can't understand why there are two kinds of Standby and Status-off threshold in the two configuration. Why does it need different voltage level? Could you help to explain it?

  • 0
    TI__Guru 58225 points

    Hello Webber,

    The LM5150-Q1 operates in one of two selectable configurations when waking up. In Start-Stop configuration (SS configuration), the device runs at a fixed switching frequency without any pulse skipping until it enters standby mode, which helps to have a fixed EMI spectrum. In Emergency-Call configuration (EC configuration), the device will skip pulses as it automatically alternates between low IQ standby mode and wake-up mode to extend the battery life in light load conditions.

    So dependent on the system it is possible to either allow a higher output voltage (+24%) in the SS configuration which automatically extends the switching time and the standby time when the device is in light load mode, compared to the EC configuration where the allowed increase in output voltage is just 12%. So if the load is ok with 24% higher output voltage, the SS configuration can help to extend the standby time, but especially when the battery is close to depletion, the wake-up time will be longer in SS configuration as well and causes higher voltage drops on the battery.

  • 0 in reply to Brigitte
    Prodigy 30 points

    Hi Brigitte

    Thanks for your description and let me know LM5150-Q1 is a regulator with pulse skipping mode appication in EC configuration. But when i read the datasheet again, i can still not understand why LM5150-Q1 does't use the same 24% setting for leaving boost mode in both SS and EC configuration. Otherwise, why does Vload have different behavior when the loading is from full load to very light load in figure12 and figure13? 

     

  • 0 in reply to Webber Chen
    TI__Guru 58225 points

    Hello Webber,

    Figure 12 is with fast Vsupply fall and slow switching. Figure 13 is with slow Vsupply fall and fast switching.

  • 0 in reply to Brigitte
    Prodigy 30 points

    Hi Brigitte

    Why doesn't LM5150-Q1 use the same 24% setting for leaving boost mode in both SS and EC configuration? If my target is EC, do you suggest LM5150-Q1 or LM5155-Q1? Thanks.

  • 0 in reply to Webber Chen
    TI__Guru 58225 points

    Hello Webber,

    In EC configuration the battery could already be relatively empty. If the output voltage is boosted up for a longer time, the battery voltage will drop more, so the risk of discharging below UVLO of the system is higher if it is boosted for a longer time which would be necessary to get to the 24% plus.

    Which device is the best one for your application, depends on your application needs. For example if light load efficiency is of high importance for your application LM5150-Q1 might be the better choice. But here you need to decide on the most important needs in your specific application.