TPS566238: About the start time of TPS566238

chunli Liang

Prodigy 220 points

Part Number: TPS566238

Tool/software:

I am reviewing the datasheet of the TPS566238, and I have three questions about the POWER START UP time.

TPS56623x 3-V to 18-V Input, 6-A Synchronous Step-Down Voltage Regulator datasheet (Rev. B)

Question 1

In Section「6.3.2 Soft Start」,

it states that "If the application needs a longer soft-start time than 0.5 ms, the time can be set by connecting a capacitor on

the SS pin" indicate that the calculation method for Tss is 0.5ms plus the value calculated by Equation 2?

Question 2

Is there a minimum capacity requirement for Css when I want to calculate the minimum time of Tss?

Question 3

I have not found any description of the Enable delay time, except in 「Figure 7-15. Start-Up Through EN」.

It shows approximately 0.2ms. Is it a typical value?

Thanks and Best Regards

Chunli Liang

24 days ago

0 Hitesh Chandwani 23 days ago

TI__Expert 3140 points

Hello Chunli,

WE will check and get back to you.

-Hitesh

0 Hitesh Chandwani 23 days ago in reply to Hitesh Chandwani

TI__Expert 3140 points

Hello Chunli,

1. You are correct that Css will introduce a softstart time additional to 0.5ms

2. There is no minimum value of the Css, you can left it floating as it will charge the minimum internal capacitor (which adds 0.5mS).

3. Unfortunately, we don't have data for this parameter but its not a typical 0.2mS, its 0.2ms on for the specific testing condition.

-Hitesh

0 chunli Liang 15 days ago in reply to Hitesh Chandwani

Prodigy 220 points

Thank you for your response.

>>3. Unfortunately, we don't have data for this parameter but its not a typical 0.2mS, its 0.2ms on for the specific testing condition.

→

I want to know what specific condition will effect the time 0.2ms?

Do you know the max value?

Thanks and Best Regards

Chunli Liang

0 Hitesh Chandwani 13 days ago in reply to chunli Liang

TI__Expert 3140 points

Hello Chunli,

I got the data for 0A and 1A, and I can see that the delay is dependent on the load current but the total startup time after the EN is high is constant.

Iout = 0A

Iout = 1A

so you can consider max 1ms for 0A and then it will decrease.

-Hitesh

0 Hitesh Chandwani 13 days ago in reply to Hitesh Chandwani

TI__Expert 3140 points

Its 2ms/ div so its 2ms maximum delay,

-Hitesh

0 chunli Liang 12 days ago in reply to Hitesh Chandwani

Prodigy 220 points

Hi Hitesh

Thank you for your quick answer.

Unfortunately, this does not meet our requirements.

In fact I want to find the Power IC(0.9V~1.1V) to supply the core voltage of CPU,

and the start time from EN to the output the target voltage is below 1.6ms for the power sequence.

Do you have any recommended parts？

Thanks and Best Regards

Chunli Liang

0 Hitesh Chandwani 12 days ago in reply to chunli Liang

TI__Expert 3140 points

Hello Chunli,

The above waveforms were with the 4 ms startup time(adjusted by capacitor)

By removing the capacitor, you can get the minimum startup time of 0.5mS.

waveforms were just to show that the startup time will be constant and the initial delay will depend upon the load.

Let me know if you need any other clarification on this.

-Hitesh

0 chunli Liang 11 days ago in reply to Hitesh Chandwani

Prodigy 220 points

Hi Hitesh

I would like to confirm in more detail.

Q1:

After removing the capacitor, the startup time from EN to the output reaching the target voltage becomes a constant 0.5ms,

even though the time of the EN delay time and Soft-Start Time (Tss) may change as shown in the figure below. Is this correct?

Q2:

The datasheet shows a soft-start time of 0.5 ms with no SS pin capacitor connected. Is there a specified tolerance for this value?

Or what is the maximum value?

Thanks and Best Regards

Chunli Liang

0 Hitesh Chandwani 11 days ago in reply to chunli Liang

TI__Expert 3140 points

Hello,

Q1: Yes you are correct EN to the output reaching the target voltage will be constant (0.5ms for no cap connected).

Q2: No we just have typical value for this data.

-Hitesh

0 chunli Liang 10 days ago in reply to Hitesh Chandwani

Prodigy 220 points

Hi Hitesh

Sorry, it may be a difficult question to answer, typ is 0.5ms.
Is it possible to reach a maximum of 1.5ms?

Thanks and Best Regards

Chunli Liang

0 Hitesh Chandwani 10 days ago in reply to chunli Liang

TI__Expert 3140 points

Hello Chunli,

If you keep SS pin floating, it won't cross 1.5mS

Variation won't be so much like 100% for 0.5mS target time. so even 1ms will be difficult to reach.

so you can use SS pin as floating.

-Hitesh

0 chunli Liang 9 days ago in reply to Hitesh Chandwani

Prodigy 220 points

Hi Hitesh

Thank you for your patient answer.

Thanks and Best Regards

Chunli Liang

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TPS566238: About the start time of TPS566238