TPS2557: ton definition

Hi Hirokazu,

Q1: The ton is around ~6ms at figure1 datasheet page7 instead of 3.8ms.

Please refer to the defination as following:

For the max value or USL value please refer to the below Char data:

Firstly, we must consider all the temperature range from -40 to 125;

Secondly, we must reserve some margin for high CPK value in order to make sure  the stability.

Q2: I am not clear with your question. For application, in and en pin connect together. For TPS2556 low EN assert will turn on part.

For TPS2557, high EN assert will turn on the part.

If any, contact me any time.

Ziv

Hello Ziv-san

Thanks for your reply.

The exampe for my Q2 is below.
For example, I assume that ton is 6ms and toff is 6ms for one sample of TPS2557.
If EN goes to Low during 3ms after EN goes from Low to High,  is the TPS2557 turned on for only a moment?

Best Regards,
Hirokazu Takahashi

Hi Hirokazu,

In datasheet TPS2557, Page7, Fig2 can answer your question.
If toff=6ms, as EN go low 3ms, the part will still keep on status for another 3ms.
Noted, Page7, Fig2 is TPS2556 which turns on as low EN.

Hello Ziv-san

Thanks for your support.
My question is attached file.

Best Regrds,
Hirokazu Takahashi

Hi Hirokazu,

If ton=6ms, means you must keep EN=6ms, then the output can change the status.

So, for this case, it only makes EN=3ms, the output will stay zero.

Ziv

Hello Ziv-san

Thanks for your reply.
How about below cases?

Best Regards,
Hirokazu Takahashi

Hi Hirokazu,

EN=6ms, the switch will turn on.

Due to toff=6ms, after on status 6ms, the switch will turn off.

The attachment is the simulation files by TINA.

TPS2557.TSC

I am not famililar how to attch the attachment. If not received, please contact me.

Thanks.

Ziv

 

Hello Ziv-san

Thanks for providing your simulation model.
EN pin is enable "charge pump" at the block diagram in the datasheet page 11. Does the delay time of ton and toff depends on the period when the charge pump needs for charging and discharge gate voltage? Could you let me know how the internal block works at the start up?
Does TPS2557 have any function avoiding glitch input? Will the delay time of ton and toff be effective to avoid glitch input?

Best Regards,
Hirokazu Takahashi

 

Hi Hirokazu,

I consulted the designer.

First, it will take time for charge pump and current sense circuit to work.

Secondly, as charge pump and current sense circuit work, the charge pump generates constant current to charge the gate which also takes some time.

That's the Ton time.

I am not clear about your second question.

Can you describe in detail?

What's glitch input? Can you tell me the application or an example?

Thanks.

Ziv

Hello Ziv-san

Thanks for your reply.
The glitch input means that noise going up and down the threshold enters the EN pin.

If such noise enters the EN pin, does the TPS2557 have the ability to ignore the noise?

Best Regards,
Hirokazu Takahashi