• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 329 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS22917L Active low datasheet

AJ
Intellectual 570 points

Part Number: tps22917L

Hi there,

Originally I was looking at TPS22917 (Active HI) load switch as part of Vcc I/O sequencing.
Due to supply constraints, the plan is to use TPS22917L (Active LO) version + an inverter as a stuffing option.

It appears the datasheet was intended for the original TPS22917 device. I presume for the Active LO version, a Smart Pullup is used to keep the ON pin from floating until system sequencing is complete. After the ON pin is deliberately driven low (≤ VIL), the Smart Pullup (Rpu) is disconnected to prevent unnecessary power loss.

Can you confirm the above statement and do you have any data on ON pin Rpu for the TPS22917L 

Best,
Alex

  • 0
    TI__Genius 13300 points

    Hello Alex,

    A smart pullup is used to pull down the device until the Vih threshold has been reached then is disconnected so that it isn't constantly draining power. It also helps to prevent anything from weakly pulling the rail up. 

    When VON is > 1V then the smart pull down is disabled. 

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Intellectual 570 points

    Hi Kalin, 

    Can you explain how a "smart" pullup is used to pull down the device...?

    Please note, my question was in relation to TPS22917L active Low version. Accordingly, the logic is inverted so there should be a pullup - not a pull down...

    Do you have more data on this smart pull up for the TPS22917L?

    Best

    Alex

  • 0 in reply to AJ
    TI__Genius 13300 points

    Hello Alex,

    Apologies, I meant to say pull-down in my previous post at the beginning. There is not a "smart pull-up". 

    It's still a pull-down to ensure the device doesn't float. The logic works for either active low or active high devices. 

    Active high device- a pull down to ground makes sure the device does not float to an active level at any point so the device stays off, and prevents the device from consuming more power when intentionally held high enabling the device but disabling the pull-down.

    Active low device- a pull down to ground ensures the device is active and does not float up to an inactive level at any point so the device stays on, and prevents the device from consuming more power when it's intentionally held high disabling the device and the pull-down.

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Intellectual 570 points

    Hi Kalin,

    Thank you for the clarification and prompt response.

    I would have assumed the device is disabled by default so a smart pull-down for TPS22917 (active HI) and a smart pull-up for TPS22917L (active lo) version. This is implied in your datasheet section 9.3.1 reads the first paragraph.

    9.3 Feature Description

    9.3.1 On and Off Control

    ... The TPS22917 is enabled when the voltage applied to the ON pin is pulled above VIH, while the TPS22917L is enabled when the voltage is below VIL.

    When power is first applied to VIN, a Smart Pulldown is used to keep the ON pin from floating until system sequencing is complete. After the ON pin is deliberately driven high (≥VIH), the Smart Pulldown is disconnected to prevent unnecessary power loss. Table 9-1 shown then the ON Pin Smart Pulldown is active.

    Table 9-1. Smart-ON Pulldown

    VON Pulldown

    ≤ VIL Connected

    ≥ VIH Disconnected

    In our application, I need to ensure the TPS22917L is OFF during startup, so I would have to add an external pullup to the ON pin

    Once the input power is ready, I would then drive ON pin low to enable the switch.

    However and assuming the TPS22917L only has a pulldown is a bit useless as driving the pin low connects the smart pull-down as per Table 9-1. Hence my question :) 

    Can you please confirm?

    Best 

    Alex 

  • +1 in reply to AJ
    TI__Genius 13300 points

    Hello Alex,

    I see why a smart pull-up would benefit your application and why the smart pull-down isn't as significant for you, but this device only has a smart pull-down for both the active high and low versions. You will need to drive the ON pin HI before VIN is applied to ensure the systems starts while the device is in an OFF mode.

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Intellectual 570 points

    Hi Kalin,

    Thank you for confirming.

    Best,

    Alex