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TPS22954-Q1: 0V9 Load Switch setting?

fusheng Yu
Prodigy 90 points
Part Number: TPS22954-Q1
Other Parts Discussed in Thread: TPS22954

Hi Sir , 

I want to design a 0.9V , 3A  Load switch by TPS22954. 

there are two questions below 

1.  the pin setting (BIAS and SNS ) , I am not sure how to setting 

On Datasheet , BIAS need to 2.5V at least.

2. the Power sequence order between Vin , VBIAS, EN , PG ?

  • +1
    TI__Genius 16145 points

    Hello, 

    • Yes Vbias will need to be at least 2.5V for the device to be biased correctly. Therefore, if your input voltage is less than 2.5V, it cannot be directly tied to Vbias. A separate voltage rail >=2.5V on Vbias will be needed for the device to function. 
    • The SNS pin is used to adjust the power good level to monitor the output voltage of the device or another voltage rail. Whatever voltage rail you want to monitor, we recommend connecting that rail to the SNS pin through a voltage divider to be used to determine when the device pulls PG low. This pin can also be tied to the voltage rail directly as long as the voltage rail is within the 5.7V max recommended specification shown below: 
    • If the voltage on the SNS pin exceeds VIH,SNS, the voltage being monitored on the SNS pin is considered to be valid high. The voltage on the SNS pin must be greater than VIH,SNS for at least tBLANK before PG is asserted high. If the voltage on the SNS pin goes below VIL,SNS, then the switch powers cycle (that is, the switch is disabled and re-enabled). For proper functionality of the device, this pin must not be left floating. If a resistor divider is not being used for voltage sensing, this pin can be tied directly to VOUT.
    • With regard to sequencing, one thing to consider is if you are ever pulling ON high when Vin/Vbias is low, we want to be sure Vbias is at least 2.5V tD (ON delay time) after Von is at 50% to be sure the device is biased correctly.

    Best Regards, 

    Elizabeth