TPS259470L startup current

Hi Yoshi-san,

By startup current, do you mean the inrush current you are seeing or is this the continuous current due to load (resistive load in nature).

By increasing the dvdt cap, we can slow down the startup speed which will result in lower inrush current. By decreasing the dvdt cap, we can make the startup faster and increase the inrush current due to cap. 

Best Regards,
Arush

Hi Arush-san

Thanks for your reply.

The startup current is this the continuous current due to load (resistive load in nature).

I determined the dvdt cap to be 0.15uF from the "TPS25947xx_Design_Calculator" Excel file provided by TI.

If the startup current (For example, 150mA) of TPS259470L is reduced, TPS259470L can start.

Can we increase the start-up current without changing Cout?

Best Regards

Yoshi.

Hi Yoshi-san,

If you can do sequential startup i.e. use PG signal from device to turn on the load (which is demanding continuous startup current), then this issue will go away immediately.

I think you know the issue but to make things clear, I am still explaining it here.

resistive load will demand continuous current and capacitive load will demand inrush current. By changing startup speed, inrush will vary. Longer startup result in lower inrush current but continous resistive load current will cause power dissipation for longer time resulting in Thermal shutdown of device. Similarly faster startup will result in higher inrush current which will cause higher power dissipation resulting in Thermal shutdown (TSD)

Now we cannot change TSD as it is based on junction temperature and it protects the mainFET (maintain SOA). 

time to TSD plot in datasheet helps in estimating this.

Now in your case, high resistive load and high capacitive load is preventing us from finding any optimum value 

Best Regards,
Arush 

Hi Arush-san

Thanks for your reply.

I understood your comment.

Could you recommend another eFuse that can drive at this high resistive load and high capacitive load?

Best Regards

Yoshi.

Hi Yoshi-san,

Do you have any specific requirements like reverse current blocking required or bi-directional current flow. Also what is your max load current?

Best Regards,
Arush

Hi Arush-san

reverse current blocking required : need

bi-directional current flow : no need

max load current : about 1A (For margin, we will set ILIM to 4A.)

Best Regards

Yoshi.