TPS25921A: Softstart operation and reverse current protection diode.

Hi Michiaki,

Please see my response inline below,

1. Isn’t pull-up resister needed at ENUV pin if UV function is disable.
   Can customer tie ENUV to more than 1.42V such as VIN ?
   1. ENUV pin is rated same as IN pin. So, you can pull it up directly to VIN.
2. Can customer tie OVP to GND directly ?
   1. YES
3. In soft start operation, inrush current exceeding ILIM will not be seen ?
   1. Inrush current will be minimum of (Iinrush, Ilim). If inrush current is set to be higher than current limit value, the device will limit the current to set current limit 
4. Maximum current is the number configured by ILIMIT at startup ?
   1. As explained above
5. In the power down, if the voltage of input pin is dropped first, external protection diode is not needed ?
   1. During output short circuit conditions, a TVS at input and Schottky at output are required. Please refer to section '11.1 Transient Protection' in datasheet.

Hi Praveen,

Regarding 5. , Should customer place the protection diode between VIN and VOUT in case input power supply disappeared ?

Thank you and best regards,

Michiaki

Hi Michiaki,

The Protection diodes TVS and Schottky are to be used w.r.t GND. These are required if there is inductance in the input and output path. 

TVS-> VIN to GND and Schottky -> VOUT to GND

Hi Praveen,

Does TPS25921x the diode highlighted red circle for protection ?

We don’t think it is needed.

Please let me double check on the above.

Thank you and best regards,

Michiaki

Hi Michiaki,

Yes, you will not require the diode from OUT to IN for protection.