TPS3840-Q1: understanding CT pin

Tamas Fenyvesi

Part Number: TPS3840-Q1

Hi,

datasheet 8.2, functional block diagram seems weird:

Nothing can pull CT down to GND.

Do you wanted to mean something with CT pin comes from the drain of the left side N-ch MOSFET; whilst the source of that MOSFET is at GND?

What happens if I tie the other pin of the timer capacitor to VDD instead of GND? Will the startup reset time be short, but a response to MR=L is a long pulse?

Thanks,

Tamas

over 3 years ago

0 Ben C over 3 years ago

TI__Mastermind 38675 points

Hi Tamas,

There are other proprietary circuits that are not shown in the block diagram.

Ben

0 Tamas Fenyvesi over 3 years ago in reply to Ben C

Prodigy 180 points

Sure, but still, isn't the meaning of the circuit something like an N-ch FET pulling down to GND directly w. lower impedance and the P-ch can pull up slowly via a resistor?

Thanks,

Tamas

0 Ben C over 3 years ago in reply to Tamas Fenyvesi

TI__Mastermind 38675 points

Hi Tamas,

I believe you have the right idea how the capacitor charges and discharges but the block diagram doesn't show everything of how the capacitor discharges. Again, there are proprietary circuits that are not being shown but have the right idea about functionality of the CT pin.

Ben

0 Tamas Fenyvesi over 3 years ago in reply to Ben C

Prodigy 180 points

Thanks

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TPS3840-Q1: understanding CT pin