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Component choice and Swap

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chrischina

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I have two questions in one:

I have collected some schematic from datasheet from manufacturer of chip. Inside the datasheet there are the following circuit shown below.

1./ The manufacturer don't provide the BOM, so I don't have part number for all those small passive components. How to decide which one to use in terms of tolerance, X5R/X7R, Voltage, package ?

2./ On some schematic there are some polarized capacit, typically some round cylinder space consumming. By what type of SMD can I replace those big cylinder to make the circuit smaller ?

While answering this question, please explain it so I can understand what logical methodology you are using accelerometer.jpgLDO.jpg
 

Hi,

Usually in the datasheet you find a section called "capacitor selection", there you find all informations you need.

Klaus
 

There are not , this is the reason of my post. Not all datasheet are always detailed.
 

1./ The manufacturer don't provide the BOM, so I don't have part number for all those small passive components. How to decide which one to use in terms of tolerance, X5R/X7R, Voltage, package ?
Click to expand...

Look at the component and ask the question: what will happen if the component is replaced with another with a different tolerance? In other words, is the specific component performing some critical task? If it is a capacitor, and you find one with a very high voltage specified, ask the question: why such a high voltage was specified? If your circuit voltage is 12V and you find some capacitors with spec of 47V, perhaps they were really not needed (25V would have been sufficient).

2./ On some schematic there are some polarized capacit, typically some round cylinder space consumming. By what type of SMD can I replace those big cylinder to make the circuit smaller ?
Click to expand...

They are performing some non-critical (filter) work and they can be safely replaced with SMD caps of suitable voltage ratings. Even the values are not critical, you can safely replace with the next lower or higher value.
 

Hi,

There are not , this is the reason of my post. Not all datasheet are always detailed.
Click to expand...


From datasheet:
Capacitor Requirements
For stability and minimum output noise, a capacitor on
the regulator output is necessary. ......
Click to expand...

--> read datasheet. There also are application notes.
If we should give advice we need to read them, too.

Klaus
 

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