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Suffering from ESR fluctuations due to temperature? Maybe it’s time to polymerise!

Equivalent Series Resistance (ESR) is dependent on frequency and temperature. It also changes as components age, so it’s a really important consideration when you’re selecting electrolytic capacitors. Losses due to ESR will limit the ability of the capacitor to source or sink charge quickly. In turn, this affects input and increases high-frequency noise, decreasing filter efficiencies.

KEMET Conductive Polymer Aluminium Solid Electrolytic Capacitors (both Single Ended/Radial and Surface Mount) are highly conductive due to a solid polymer electrolyte, which means they generate less heat internally during operation. Features include low ESR, higher ripple capability, open failure mode, and greater stability across a wide range of operating temperatures. This ensures suitability for industrial and commercial applications such as mobile phone chargers, computer motherboards, servers and adapters, as well as medical, LED driver, industrial power and automotive infotainment.

KEMET’s through hole form factor capacitors have a temperature range of -55°C to +105° and -55°C to +125°C, with voltages from 2.5 to 250 VDC offering extra-long life up to 5,000 hours. SMD form factor capacitors feature a temperature range from -55°C to +105°C and voltages from 2.5 to 50 VDC, offering long life up to 2,000 hours. Regardless of form factor, KEMET capacitors offer high-performance specifications in miniature size for the most demanding applications.

Through hole capacitor comparison 

A750

A755

A758

A759

47 - 1,500 µF

47 - 1500 µF

10 - 1200 µF

2.2 - 680 µF

2.5 – 25 VDC

2.5 – 25 VDC

2.5 – 25 VDC

35 – 250 VDC

-55°C to +105°C

-55°C to +105°C

-55°C to +105°C

-55°C to +125°C

2,000 hours

5,000 hours

5,000 hours

2,000 hours

Through hole

Through hole

Through hole

Through hole

Low impedance

Low impedance

Miniature

Low impedance

High ripple current

High ripple current

Low impedance

High voltage

RoHS compliant

Long life

High ripple current

High ripple current

 

RoHS compliant

Long life

High temperature

 

 

RoHS compliant

RoHS compliant

 

Typical examples for A750 (124-8265) (124-8270) (124-8269) (124-8268) (124-8257) (124-8261)

Surface mount capacitor comparison 

A765

A767

10 - 2700 µF

18 - 220 µF

2.5 – 35 VDC

35 – 50 VDC

-55°C to +105°C

-55°C to +105°C

2,000 hours

2,000 hours

Surface mount

Surface mount

 Miniature

Ultra-low impedance

Ultra-low impedance

High ripple current

High ripple current

High voltage

RoHS compliant

RoHS compliant

 

Expected Life

The life expectancy of Polymer capacitors can be significantly greater than standard electrolytic capacitors and the effect of temperature derating is a really big deal. Instead of doubling life with every 10°C temperature decrease, as with standard electrolytic capacitors, life will be 10 times longer with every 20°C temperature decrease. For the same 20°C decrease, the life expectancy of an aluminium electrolytic capacitor increases by a factor of 4, while an aluminium polymer capacitor increases by a factor of 10. Expected life depends on operating temperature according to the following formula:

L = Lo x 10 (To-T)/20

Where:

L:   Expected life

Lo: Life at maximum permissible operating temperature with rated operating voltage applied (hours)

T:  Actual operating temperature

To: Maximum permissible operating temperature


Expected Life Calculation Chart

 

Expected Life with Temperature Derating

 

Temperature Stability Characteristics

Stable characteristics in a very-low-temperature range allow for fewer circuits in design.

Due to a solid polymer electrolyte, KEMET’s Conductive Polymer Electrolytic Capacitors feature higher conductivity.

This results in a lower ESR across the temperature range which, coupled with high capacitance, allows an Aluminium Polymer Capacitor to replace several standard electrolytic capacitors, reducing the number of components and maximising board space.

When comparing a 47uf, 250V 8x12mm standard electrolytic and conductive polymer electrolytic cap, you can see that the ESR of the polymer cap is nearly constant (a deviation of less than 233 milliohms within its operating temperature range, while the ESR of the electrolytic cap noticeably changes (up to 254 ohms) with temperature.

The low ESR is also a really big deal!

 

Ripple Current Characteristics

The highly conductive polymer results in a lower ESR, therefore Aluminium Polymer Capacitors are able to withstand higher ripple currents during normal operation that are significantly higher than other electrolytic capacitors.

KEMET Conductive Polymer Aluminium Solid Electrolytic Capacitors (Single Ended/Radial and Surface Mount) offer longer life and greater stability across a wide range of temperatures. Polymer capacitors use conductive polymers as the electrolyte. Liquid electrolytes that are present in standard electrolytic capacitors are replaced with a solid PEDOT polymer electrolyte. By using a solid electrolyte, conductivity is greatly increased, as well as being stabilised. This cures age-old issues of high viscosity and electrolyte evaporation, resulting in increased internal resistance and a swifter end of life. Electrolyte drying is one the factors that limit the lifetime of standard electrolytic capacitors. So, maybe it’s time for you to polymerise your capacitors!

DesignSpark Community Manager and all-around geek girl.