23 June 2005
HE104MAN-V8 Manual
3.5 Filter Capacitors
At 10kHz and above, the impedance of filter capacitors is essentially their effective series resistance (ESR) and this parasitic resistance limits the filtering effectiveness of the capacitors. The filter capacitors absorb the “switching ripple” current with their 100m0hm ESR that absorbs a 5A ripple current and will dissipate 2.5W of heat.
The capacitors used for filtering in the HE104 are organic semiconductor
-Very low ESR values, less than 8 times lower for same package.
-High ripple current rating, over 4 times higher for same package.
-No degrade in operation at extended low temperatures. (ESR value of conventional electrolytics can increase 25 fold at
The life expectation for a filter capacitor is typically 2,000 to 6,000 hours @ 105C. For a conventional electrolytic capacitor the temperature acceleration coefficient = 2 for a 10C increase, while the OS- CON has a temperature acceleration coefficient = 10 for a 20C increase. For example, a capacitor rated for 2,000 hours @ 105C would have an expected life of:
For conventional electrolytic capacitor 32,000 hours (3.6 years) @ 65C 128,000 hours (14.6 years) @ 45C
For
200,000 hours (22 years) @ 65C
2,000,000 hours (220 years) @ 45C
This means that the
In a buck convertor, output ripple voltage is determined by both the inductor value and the output filter capacitor (for continuous mode).
ESR ∙ Vout ∙ (1- (Vout))
Vin
Vp –p
L1 ∙ frequency
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