[SOLVED] inductance value for mcu filtering

[h.galeh]

in microcontrollers we use inductors and capacitors for filtering
I have "Blueboard_lpc1768_H_schematics" but there is a problem
inductance is not specified . how much should it be
why we use such value

 

[hpb]

in microcontrollers we use inductors and capacitors for filtering
I have "Blueboard_lpc1768_H_schematics" but there is a problem
inductance is not specified . how much should it be
why we use such value

the inductance is though used for filtering purpose, it also used for current suppression. since in the circuit shown the inductors are connected nearer to V+ and V- their main function is to protect the circuit from the over-current. the value is dependent on the inductor spec. for the required amount of current demand.

 

[chuckey]

It all depends on the frequency of the interference you are dealing with such as a clock frequency,their value is not critical, I would try 100 micro henries rated at the supply current which seems to be 3A (3V3A?)
Frank

 

[FvM]

BLM is a series of Murata filter ferrites. They are essentially lossy inductors and specified by an impedance number, that's missing in the schematic. Personally, I would use Z=300 to 600 ohm in this place (low current analog supply or reference filtering).

Pure LC filters are at risk to create oscillations with pulsed loads, e.g. digital supply pins.

 

[h.galeh]

frequency is 80~100MHz
voltage: 3.3v
top left of schematic