# value of decoupling capacitor

#### Dimpi

Joined Sep 6, 2013
96
what should be the specific values of decoupling capacitors taken for the pins of usb port inbuilt in MSP430 microcontroller?
please tell me the exact way to calculate the value of decoupling capacitor when voltage suppliesd is known??

One more doubt i m having- is the bypass capacitor same as decoupling capacitors???if different what is the specific diff between the two??

#### skeptor

Joined Feb 5, 2013
15
what should be the specific values of decoupling capacitors taken for the pins of usb port inbuilt in MSP430 microcontroller?
please tell me the exact way to calculate the value of decoupling capacitor when voltage suppliesd is known??

One more doubt i m having- is the bypass capacitor same as decoupling capacitors???if different what is the specific diff between the two??
hey there,

to put simply yes the bypass capacitor is the same as decoupling capacitor, since it is used to bypass the power supply.

to answer your question about how to calculate the capacitor values check out the following link:

http://www.ti.com/lit/an/scaa048/scaa048.pdf

A 100nF capacitor is used commonly, since it is cheap and mostly covers the required range.

#### Dimpi

Joined Sep 6, 2013
96
ok the calculation which is given in the sheet (http://www.ti.com/lit/an/scaa048/scaa048.pdf)is understood but

i dont know about any value except the voltage that the vbus pin of usb connector is providing to the the usb2.0 port of MSP430??so now how to do calculations??or blindly we can take the value as 0.1uf??

#### skeptor

Joined Feb 5, 2013
15
ok the calculation which is given in the sheet (http://www.ti.com/lit/an/scaa048/scaa048.pdf)is understood but

i dont know about any value except the voltage that the vbus pin of usb connector is providing to the the usb2.0 port of MSP430??so now how to do calculations??or blindly we can take the value as 0.1uf??
why don't you go through the datasheet and the architecture of them to be sure.Besides, i do not understand what exactly you are trying to do.... in order for anyone to give a better explanation, it is better to have a project description.

#### Dimpi

Joined Sep 6, 2013
96
yes i have gone through the datasheet,it is mentioned that the decoupling capacitors to be placed in the v18,vbus and vusb line of MSP430 microcontroller(in which usb is inbuilt)..but the exact values of capacitors are not specified..i hope m clear this time.

should i take the value 0.1 uf ??or some more things i need to study from datasheet??please help.

#### skeptor

Joined Feb 5, 2013
15
yes i have gone through the datasheet,it is mentioned that the decoupling capacitors to be placed in the v18,vbus and vusb line of MSP430 microcontroller(in which usb is inbuilt)..but the exact values of capacitors are not specified..i hope m clear this time.

should i take the value 0.1 uf ??or some more things i need to study from datasheet??please help.
okay here is what i'd like you to do, give a description of which micro controller you are using and what is your application.

#### Dimpi

Joined Sep 6, 2013
96
m using MSP430 microcontroller.m trying to make a gps gsm based tracking device...now i am dealing with the jtag section,usb section so i need to put bypass or coupling capacitors ..how to decide its value..

#### MrChips

Joined Oct 2, 2009
21,304
It is common practice to use a 0.1μF in parallel with a 10μF electrolytic capacitor across the power supply.

#### skeptor

Joined Feb 5, 2013
15
m using MSP430 microcontroller.m trying to make a gps gsm based tracking device...now i am dealing with the jtag section,usb section so i need to put bypass or coupling capacitors ..how to decide its value..
i would say use the 100 nf (0.1µF) as a decoupling cap should work just fine.