EEVblog Electronics Community Forum

Electronics => Beginners => Topic started by: Vindhyachal.takniki on January 20, 2015, 09:49:29 am

Title: 10uf tantalum capcitor adxl375
Post by: Vindhyachal.takniki on January 20, 2015, 09:49:29 am
1. Adxl375 specifically mentioned about using 10uf tantalum capacitor on Vs.
2. What the reason for that?
3. What if I use 10uf ceramic for that.


I have read on internet thet ceramic has below drawbacks:
1. Aging
2. Voltage coeff
3. Piezeo noise
4. Flex crack (most severe)


After reading I guess since adxl375 is used for measuring accelration so most dominating reason to use 10uF tantalum will be piezo noise. Is it right?
But along with 10uF tantalum, datasheet specify to use 0.1uF ceramic also, which may go opposite to my above reason.
I want to know what exactly the reason for using tantalum here.
Title: Re: 10uf tantalum capcitor adxl375
Post by: T3sl4co1l on January 20, 2015, 08:58:21 pm
Tantalum provides supply damping due to ESR.  An acceptable substitute may be a ceramic capacitor of the same value, in series with a chip resistor of a few ohms (to replace the internal ESR of the tantalum).

Exact values depend on what else is connected to the supply as well.

Tim
Title: Re: 10uf tantalum capcitor adxl375
Post by: wraper on January 21, 2015, 02:18:08 am
Tantalum provides supply damping due to ESR.  An acceptable substitute may be a ceramic capacitor of the same value, in series with a chip resistor of a few ohms (to replace the internal ESR of the tantalum).

Exact values depend on what else is connected to the supply as well.

Tim
Few ohms would make it more like electrolytic cap ESR, not tantalum. Unless there is ceramic capacitor unfriendly LDO nearby to this capacitor (low track resistance), no issues with using ceramic as it is. If going to use Y5V or Z5U type, do not forget that they change capacitance drastically with temperature and applied voltage. X7R is far from ideal too, especially when applied voltage is more than half of rated, depends on actual capacitor model though.