TPS22919: rise time(slew rate)

Hi Mukuno-san,

Thanks for your questions about the TPS22919!

You're correct, the slew rate for the TPS22919 is a constant 2.3 mV/μs because this package has no configurable rise time feature. Therefore, the rise time is constant. 

Since the customer is using a relatively large CL, I went ahead and ran the calculations to ensure inrush current will not be an issue. I have included those as follows:

For when CL = 100uF, Inrush current = (Slew rate)(CL) = (2.3 x 10^-3/10^-6)(100 x 10^-6) = 230 mA

For when CL = 120uF, Inrush current =(Slew rate)(CL) = (2.3 x 10^-3/10^-6)(120 x 10^-6) = 276 mA

Since both inrush currents < 1A, this larger CL should not cause excessive inrush current. 

Please let me know if you have any more questions about the TPS22919.

Best regards,

Rachel Richardson

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Hi Richardson-san,

Thank you for your answer.

I would like to confirm you about the value of 2.3mV/us.

I think, Slew rate spec is described 3.2mV/us at 5Vin, 2.7mV/us at 3.3Vin, 1.8mV/us at 1.8Vin.

However, Slew rate 2.3mV/us is described in 9.2.2.1 Limiting Inrush Current. What is 2.3mV/us?

Also, Ton(Tdelay+Trise) time is depend on output capacitor like as Figure10.

Could you please let me know the Ton time and Trise time at CL=120uF and VIN=5V?

Thanks

Muk

Hi Mukuno-san,

Thank you for bringing this to our attention. This is a typo in the TPS22919 datasheet which we will work to rectify as soon as possible. The 2.3mV/us slew rate listed should really be 2.7mV/us. If you look at Table 3, the design parameters for this design example are VIN=3.6V and CL=47uF. When VIN=3.6V, the slew rate is 2.7mV/us, as you mentioned above. I apologize for this error and not catching this when assisting you in my first response.

While we do not have specific data when CL=120uF and VIN=5V, we will run a test on the EVM with that load capacitor value and capture these timing characteristics for design reference. I will be in touch with you shortly with our t_on and t_rise findings. Thank you for your patience. 

Best regards,

Rachel Richardson 

Hi Richardson-san,

Thank you for your supporting.

I wait your test results.

Thanks

Muk

Hi Richardson-san

I appreciate your kindly support!!

Thanks

Muk

Richardson-san,

Customer requested the waveform for your test.

Could you please give me the waveform?

Also, could you please let me know the test temp? is it room temp, right?

Thanks

Muk