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Original question:

TPS22811: Simple Load Switch

TPS22811: Doesn't power on downstream devices

Aria10
Prodigy 130 points
Part Number: TPS22811

Tool/software:

So, I try to connect this between a battery charger/battery (currently USB-PD-CHG-EVM from TI) and my load. 
When I have the battery charger with 3S batteries connected to my load, it works absolutely fine on power up. 
When I have my load switch (TPS22811EVM) connected in line, the load turns on for a while and then turns off and then tries to power on again. 

It almost feels it couldnt handle the output slew requirements, so I removed the jumper from  J15. That didnt help either. 

J1 jumper is set to 5-6 as default. 

Also now that I was playing with the jumpers, the EVM has completely stopped working even though there is a valid input. 

So I have two problems---

1. How to get the load switch to function in my design (as I am designing it in)

2. Why is my EVM not working?

  • 0
    Prodigy 130 points

    It also appears that Vout drops from 11.7V to 7ish volts when the glitch happens. Which makes sense that my downstream devices are drawing more current, but why is it causing problem when I have the load switch in place and not when I directly connect to my battery

  • 0 in reply to Aria10
    Prodigy 130 points

    Should I remove the 220uF capacitor?

  • 0 in reply to Aria10
    TI__Mastermind 38885 points

    Hi Aria,

    This device supports inrush current limiting. During startup, if very high current is drawn by load + output capacitor, the device will limit the current and this extra power dissipation can cause thermal shutdown.

    How much current is your load drawing (during normal and glitch scenario)

    Removing J15 will make the startup faster so that should help if the load type is resistive. In case of capacitive load, the inrush will become higher. So, removing 220uF and keeping J15 OPEN should allow the device to turn on.

    Aria10 said:
    1. How to get the load switch to function in my design (as I am designing it in)

    I suspect high current during startup is the cause of failed startup.

    Best Regards,
    Arush