TPS2663: To understand the tdVdT

Eric Lai

Expert 4940 points

Part Number: TPS2663

Hi Expert,

Below is the questions will need your comment to clarify.

There are tdVdT = 20.8 × 103 × V(IN) × C(dVdT) in the equation 1.

1)May we know why 20.8 is used here?

2) If we fixed the CdVdT (from same cap on the dVdT pin) in the design with same Vin now. Since the slew rate is fixed now. Whether lower or higher the out capacitance in this case, the output rising time should the same as well?

Thanks

Best regards,

Eric Lai

Field Application Engineer

Texas Instruments Taiwan Limited

O: +886-2-2175-2582

M: +886-909-262-582

E-Mail:Eric.Lai @ti.com

over 4 years ago

+1 Rakesh over 4 years ago

TI__Guru** 107051 points

Hi Eric,

Thanks for reaching out!

1A) 20.8 is due to the internal circuit design.

2A) Correct. If Vin and CdVdT values are fixed, output rise time and output ramp rate remains constant. It is independent of Cout

Best Regards, Rakesh

0 Eric Lai over 4 years ago in reply to Rakesh

TI__Expert 4940 points

Hi Rakesh ,

Thanks.

Now the customer's design is configured the 0.22uF on the dVdT pin.

The input is 12V and the output cap is 41uF.

But the vout rising time is 484 uS only.

Can you advice how to check this?

Eric Lai

0 Rakesh over 4 years ago in reply to Eric Lai

TI__Guru** 107051 points

Hi Eric,

For 0.22uF dVdT capacitance, you should get Vout rising time as 49 ms (approx). Can you check the capacitance value ?

Please share dVdT pin voltage and Vout voltage waveforms to check.

Best Regards, Rakesh

0 Rakesh over 4 years ago in reply to Rakesh

TI__Guru** 107051 points

Hi Eric,

Closing here as you are following up on email.

Best Regards, Rakesh

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TPS2663: To understand the tdVdT