1.Working Voltage
Capacitor fail is affected big by rate of working voltage and rated voltage working voltage. Please considering capacitor reliability when design practical circuits and lower the voltage.
Please set voltage below 1/3 of rated voltage when applied in low-impedance circuit (especially filter capacitor in the switch power), and below 2/3 in other circuit.
It will increase the risk of DC surge current fail when applied in low-impedance circuit with capacitors in parallel. Also, please pay attention to the stored charge in parallel capacitors and discharge them by other capacitors.
In the circuit, tantalum capacitors should control the shock of instant big current, and we suggest to use capacitors in series to remit the shock. Please parallel protective resistors over 3Ω/V on capacitors to control current below 300mA. Please make sure the working voltage is below 1/3 rated voltage when protective resistors can not be inserted.
2.Reverse Voltage
Reverse voltage are forbidden to add to solid tantalum capacitors on common condition. If can not avoid, little amount reverse voltage ( ≤100%10%UR or 1V _pick min one in 25℃ )in short time can be added.Please use bipolar capacitors first if there are reverse voltage in long time. CA30 and CA35 series wet tantalum capacitors can’t withstand reverse voltages. They must be rejected if reverse voltages process flue over them in testing, even if all parameters still qualified. Multimeter is forbidden to test resistance of tantalum capacitors regardless of polarity.
3.Failure Factors
Tantalum capacitor fail rate is lower if actually voltages added to ends of it is lower than rated voltage. The fail rate is tested under 85℃ with Max load. We recommend working voltage as 1/2 of rated voltage because voltage or current peak impact and wave current often exist in real circuit. Lower voltage design should based on category voltage if under condition that temperature over 85℃，besides, category voltage is 0.65 times of rated voltage.
Another factor affecting the failure is the series resistance connect with capacitors, the bigger of ESR in circuit the failure rate is lower.
Failure Class: L(2.0%/1000h), M(1.0%/1000h), P(0.1%/1000h), R(0.01%/1000h), S( 0.001%/1000h)
4. Ripple Current
DC bias and AC voltage peak value shall not exceed the rated voltage of the capacitor. AC and DC bias and negative peak and shall not exceed the value of reverse voltage capacitors allow. The ripple current flowing through the capacitor power loss resulted in increased product temperature thermal breakdown probability, there is a need in the circuit of ripple current limits or permissible capacitor power loss. All kinds of solid tantalum capacitors by hull number, valid values for the maximum ripple current (85 ℃ 40KHz 0.66UR) are shown in table 1, in different voltage, see table 2 frequency ripple current coefficients.
Table 1: Max ripple current of non solid tantalum electrolytic capacitor (valid values)
|
Shell No. |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
|
Ⅰrms(mA) |
40 |
50 |
105 |
280 |
380 |
500 |
600 |
750 |
850 |
Table 2: Ripple Current Coefficient
|
Frequency |
Temp ℃ |
Working Voltage |
UR |
0.9UR |
0.8UR |
0.7UR |
0.66UR |
|
120Hz |
＜55 |
specified value |
0.6 |
0.6 |
0.6 |
0.6 |
0.6 |
|
82 |
0.39 |
0.46 |
0.52 |
0.58 |
0.6 |
||
|
105 |
- |
- |
0.35 |
0.44 |
0.46 |
||
|
125 |
- |
- |
- |
- |
- |
||
|
800Hz |
＜55 |
0.71 |
0.71 |
0.71 |
0.71 |
0.71 |
|
|
82 |
0.43 |
0.55 |
0.62 |
0.69 |
0.71 |
||
|
105 |
- |
- |
0.42 |
0.52 |
0.55 |
||
|
125 |
- |
- |
- |
- |
0.32 |
||
|
1KHz |
＜55 |
0.72 |
0.72 |
0.72 |
0.72 |
0.72 |
|
|
82 |
0.45 |
0.55 |
0.62 |
0.70 |
0.72 |
||
|
105 |
- |
- |
0.42 |
0.52 |
0.56 |
||
|
125 |
- |
- |
- |
- |
0.32 |
||
|
10KHz |
＜55 |
0.88 |
0.88 |
0.88 |
0.88 |
0.88 |
|
|
82 |
0.55 |
0.67 |
0.78 |
0.85 |
0.88 |
||
|
105 |
- |
- |
0.52 |
0.64 |
0.68 |
||
|
125 |
- |
- |
- |
- |
- |
||
|
40KHz |
＜55 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
|
|
82 |
0.63 |
0.77 |
0.87 |
0.73 |
0.77 |
||
|
105 |
- |
- |
0.59 |
- |
0.45 |
||
|
125 |
- |
- |
- |
- |
0.4 |
||
|
100KHz |
＜55 |
1.1 |
1.1 |
1.1 |
1.1 |
1.1 |
|
|
82 |
0.69 |
0.85 |
0.96 |
0.07 |
1.1 |
||
|
105 |
- |
- |
0.65 |
0.8 |
0.95 |
||
|
125 |
- |
- |
- |
- |
0.5 |
Note: Ultimate value of allowed power loss(polar) depends on products heat sink condition, such as heat sink area, heat conductivity, service enviroment, etc. Voltage reduce design should be considered if high reliability or all components need to be sealed.
5.Working Temperature
Please use capacitors within the temperature range specified data sheet. Please lower voltage as working voltage when temperature over 85℃. Temperature is one of the main electrical characteristics of tantalum capacitors, so when temperature changes obvious, please confirm circuit characteristic under the min and max temperature of capacitors.
6. Reliability
Tantalum capacitor failure rate differ per applicated condition (environmental temperature, voltage, resistance, circuit, and so on), so do adequately use conditions and select the appropriate product.
(1) Failure rate of capacitors designed generally based on failure rate under 85℃ apply rated voltage continuously 1000hs. Voltage and current peak pack, ripple current and other unexpected things exist in real circuit, so lower voltage design is needed, and we suggest reduced below 65%UR(rated voltage) as normal.
(2) When apply to safety devices, please pay attention to following points to prevent shut-cut, open circuit in order to insure safety.
* Add protective circuit and protective unit, use in set to insure safety.
*Add redundant circuit. When one unit fail, it won’t affect the other units of whole system.
(2) Completly discharge non solid electrolyte tantalum capacitor before leakage detective with
