TPS22965: miscellaneous questions

Kazuhiko Hirano

Part Number: TPS22965

Hello,

My customer has some questions about TPS22965 as follows.

Q1:
When ON changes from high to low, it is guaranteed that the FET between VIN and Vout always gets off before the FET between Vout and GND gets on under all PVT variations regardless of external component values?

Q2:
They would like TI to estimate tr with the following conditions.
Vin=Vout=Vbias=3.3V
CL=200uF
RL=10Kohms/100Kohms(Though RL gets <10ohms during normal operation, but at startup, the load does not consume such large current.)
CT=1000pF
Ta=2oC

Q3:
At their app, CL is 200uF.
Though datasheet recommend CIN/CL = 10/1, CIN =2000uF is too large to fit their PCB size.
Instead, they would like to put an external power diode between Vout and Vin in parallel with the body diode to protect it. Does TI have any comments on this?

Best regards,

K.Hirano

over 4 years ago

0 Kalin Burnside over 4 years ago

TI__Genius 13300 points

Hello Hirano-san,

Q1. The FET between VIn and Vout is guaranteed to be off before the FET between Vout and ground for QOD functionality is on over temperature, process and voltage. The internal logic does not allow for both to be on at the same time.

Q2. Are you asking for a simulation or bench data?

Q3. The primary reason a 10:1 input to output capacitance is recommended is to protect the supply. If your supply is strong enough to provide the inrush current without the supply voltage dropping then it is fine to not follow the 10:1 recommendation.

Regards,

Kalin Burnside

0 Kazuhiko Hirano over 4 years ago in reply to Kalin Burnside

TI__Genius 15118 points

Kalin,

Thank you for your responses.
At Q2 Ta=2oC is my typo. Ta=25oC by right.
I am asking simulation.

Best regards,

K.Hirano

0 Kalin Burnside over 4 years ago in reply to Kazuhiko Hirano

TI__Genius 13300 points

Hello Hirano-san,

Just an FYI- simulations can take over a month in turn-time; however, if you think bench data would be fine instead I could do that by the end of the week. Let me know if you're set on a simulation and I'll fill out the request.

Regards,

Kalin Burnside

0 Kazuhiko Hirano over 4 years ago in reply to Kalin Burnside

TI__Genius 15118 points

Kalin,

The bench test is fine.
I am sorry I though simulation was easier, but I was wrong.

Best regards,

K.Hirano

0 Kalin Burnside over 4 years ago in reply to Kazuhiko Hirano

TI__Genius 13300 points

Hirano-san,

No problem. I will have the bench data to you by the end of this week.

Regards,

Kalin Burnside

0 Kazuhiko Hirano over 4 years ago in reply to Kalin Burnside

TI__Genius 15118 points

Kalin,

Thank you very much for taking care of this.
I look forward to getting the test results this weekend.

Best regards,

K.Hirano

+1 Kalin Burnside over 3 years ago in reply to Kazuhiko Hirano

TI__Genius 13300 points

Hello Hirano-san,

Here is the timing data I collected for you. Also just to be clear: the rise time will be a bit slower than the values in the datasheet table due to Vbias = 3.3V.

TPS22965	tR	tF	tON	tOFF
10kΩ	2.156 mS	100.6 mS	1.995 mS	17.19 mS
100kΩ	2.290 mS	96.98 mS	1.993 mS	16.00 mS

If you have any questions please feel free to reach out.

Regards,

Kalin Burnside

0 Kazuhiko Hirano over 3 years ago in reply to Kalin Burnside

TI__Genius 15118 points

Kalin,

Thanks a lot!

Best regards,

K.Hirano

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TPS22965: miscellaneous questions