TPS25940 Selectable ILIM control

LeonardEllis

Other Parts Discussed in Thread: TPS25940

I'm looking at a design for the TPS25940 where the ILIM resistor can be changed, thereby changing the ILIM setting of the TPS25940. The ILIM resistor value will be switch using a FET in series with the resistor, all FETs tied to the ILIM pin.

Is this an acceptable way to change the ILIM as required for a specific application? Any downside to this method?

~Leonard

over 9 years ago

0 Venkata Nandam over 9 years ago

TI__Intellectual 2800 points

Hi Leonard,

FET can be used to switch the current limit resistors. Is it required to change the current limit dynamically on-the-fly? If that is the case, you may need to verify the device functionality during high to low and low to high transitions.

Regards,
Venkat

0 LeonardEllis over 9 years ago in reply to Venkata Nandam

TI__Guru 71526 points

Without causing an OCP event, how would the functionality be checked when the FET is switched? Or are you saying switch the FETs one at a time, not simultaneously? If I have FET1 ON, and want FET2 ON, first switch FET2 ON, then switch FET1 OFF, that way, there will always be a resistor connected to the SET pin.

~Leonard

add> Actually, we were planning to use EN to set the TPS25940 OFF during the resistor value change. Would this be the preferred way, rather than as described above??

0 Venkata Nandam over 9 years ago in reply to LeonardEllis

TI__Intellectual 2800 points

Hi Leonard,

Second method is the best way. Use EN to turn off the TPS25940, then switch FETs for different current limit.

Regards,
Venkat

0 LeonardEllis over 9 years ago in reply to Venkata Nandam

TI__Guru 71526 points

but just wondering what happens with the ILIM pin floating? If the EN is used, that shuts-OFF the TPS25940, but if the voltage rail is still needed to power the product, this would not be feasible, correct?

0 Venkata Nandam over 9 years ago in reply to LeonardEllis

TI__Intellectual 2800 points

Hi Leonard,

Our device can detect open or short LIM. When LIM is open, current limit is set to 0.45A.

Enable can be driven from MCU, or system can be powered down and before making the FET switch-over.

Regards,

Venkat

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TPS25940 Selectable ILIM control