# drive strength defintion base on charging capacitor

#### yef smith

Joined Aug 2, 2020
188
Hello,if we imagine the system bellow. the value of the capacitor voltage is given as following.
RC is the rate at which the voltage is rising.
I read that drive strength is a current and the higher current the fastest the capacitor will charge.
But as i see it drive strength is RC,RC desides the charging rate of the capacitor.
What is the drive strength mathatickly?

#### ericgibbs

Joined Jan 29, 2010
12,260
hi yef,
I do not follow what you are asking, is it about the Time Constant for an R/C circuit.?
E

#### yef smith

Joined Aug 2, 2020
188
Hello Eric, i am asking regarding what its exactly drive strength in the buffered system i showed in the plot.

#### Papabravo

Joined Feb 24, 2006
15,518
Hello Eric, i am asking regarding what its exactly drive strength in the buffered system i showed in the plot.
You need to be more precise. It is not clear to me what you think "drive strength" is exactly. It is true that the size of R will limit the charging current. The voltage is actually the time integral of the current divided by the capacitor value.

#### yef smith

Joined Aug 2, 2020
188
Hello Papabravo,i am trying to know what is exactly drive strength in signal integrity

#### crutschow

Joined Mar 14, 2008
26,775
Hello Papabravo,i am trying to know what is exactly drive strength in signal integrity
Sorry, but there is a language translation problem
I don't see how "drive strength" whatever that is, relates to "signal integrity".

Are you trying to determine how to drive the two MOSFET circuit you show (with undetermined MOSFET polarity type) to get a specific output response?
If so we need more detail about that circuit.

#### Papabravo

Joined Feb 24, 2006
15,518
Hello Papabravo,i am trying to know what is exactly drive strength in signal integrity
My point is that drive strength is a term of limited precision. In this context it is hard to see just what you are talking about. If it means something along the lines of "ability to source or sink current", then we can say that it does not come from the product of R & C.