TPS7A4701-EP: Current limiting capability

Edward Banner

Part Number: TPS7A4701-EP
Other Parts Discussed in Thread: LM117

Tool/software:

Hi all

Could the NR pin be used to effect a current limit on the output, i.e. could you use an NPN transistor to pull this pin low and so lower the output voltage from a control loop sensing the input current to IN pin?

Edba

2 months ago

0 Daniel Esparza 2 months ago

TI__Expert 3965 points

Hello Edba,

The NR (noise reduction) pin should not be driven with external voltages and/or current and it is only intended for noise reduction purposes. Driving the NR pin will cause unexpected behavior and may damage the device. You may want to drive the SENSE/FB pin instead and use it as an adjustable regulator. Be mindful of the power dissipation across the pass element.

If you want to add external circuitry to control the current, you could cascade an LM117 in series and drive the adjustable pin to achieve your goal - see section 9.2 for Typical Applications in the datasheet (https://www.ti.com/lit/ds/symlink/lm117.pdf).

Regards,

Daniel

0 Edward Banner 2 months ago in reply to Daniel Esparza

Prodigy 130 points

You mean place an LM117 in series with the input and configure to be a current limiter?

Edba

0 Daniel Esparza 2 months ago in reply to Edward Banner

TI__Expert 3965 points

Hi Edba,

Yes, placing the LM117 regulator in series at the input will help limiting the current.

Best regards,

Daniel

0 Edward Banner 2 months ago in reply to Daniel Esparza

Prodigy 130 points

On page 20 of the data sheet it says Pd = (Vout - Vin) x Iout. Shouldn't this be Pd = (Vin - Vout) x Iout?

0 Daniel Esparza 1 month ago in reply to Edward Banner

TI__Expert 3965 points

Hello Edba,

Thank you for pointing it out. We will update the datasheet on the next revision to reflect the correction in the formula.

Regards,

Daniel

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TPS7A4701-EP: Current limiting capability