TPS2552-1: R_ds during a current limit operation.

Ryoma Ohashi

Part Number: TPS2552-1

Hi team,

In the datasheet 10.1.1 Constant-Current vs Latch-Off Operation and Impact on Output Voltage, it says:

"During current-limit operation, the N-channel MOSFET is no longer fully-enhanced and the resistance of the device increases"

Does this means that during current-limit operation, the driver changes the Vgs of the internal FET continuously with a feedback control to make the Iout constant, like an LDO?

Or, does the R_ds become a constant value in a current-limit operation? If so, can you provide I_lim vs R_ds characteristic?

Regards,

Ohashi

over 3 years ago

0 Kuno Wu over 3 years ago

TI__Mastermind 18556 points

Hi Ohashi,

Yes, you are correct, when the current limit happen, it will work in the saturation region.

Best Regards,

Kuno

0 Ryoma Ohashi over 3 years ago in reply to Kuno Wu

TI__Expert 5735 points

So, it means that R_ds is not constant and varies to keep the Iout to be constant, right?

+1 Kuno Wu over 3 years ago in reply to Ryoma Ohashi

TI__Mastermind 18556 points

Hi Ryoma,

Yes, it will work in the saturation region, so the Iout is constant, and VDS is changing, so the R_ds is changing. But if the current limit is not happen, it will work in the Ohmic, so the R_ds is constant. And when you change the current limit value, actually you are changing the Vgs of the TPS2552-1.

Best Regards,

Kuno

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TPS2552-1: R_ds during a current limit operation.