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  • 參數(shù)資料
    型號: T212C105J050DSC
    廠商: KEMET Corporation
    英文描述: TANTALUM HERMETICALLY SEALED / AXIAL
    中文描述: 鉭密封/軸流
    文件頁數(shù): 79/84頁
    文件大?。?/td> 590K
    代理商: T212C105J050DSC
    1.
    Dissipated power must not exceed the limits
    specified for the Series.
    2.
    The positive peak AC voltage plus the DC voltage
    must not exceed the maximum working voltage permitted
    at the ambient temperature.
    3.
    The negative peak AC voltage, in combination
    with the DC voltage, must not exceed the permissible
    reverse voltage at the ambient temperature.
    The rms ripple voltage limitation imposed by power
    dissipation is given by:
    E
    2
    R
    Z
    2
    P = I
    2
    R=
    where: I = rms ripple current (amperes)
    E = rms ripple voltage (volts)
    P = power (watts)
    Z = impedance at specified frequency
    (ohms)
    R = equivalent series resistance at
    specified frequency (ohms)
    Maximum allowable rms ripple voltage may be
    determined as follows:
    E(max) @
    25°C=Z
    E(max)
    E(max) @
    P(max)
    =
    85°C=0.9 E(max) @ 25°C
    125°C=0.4 E(max) @ 25°C
    maximum watts shown on
    Performance Characteristic pages 5,
    42, 49, 58 and 61.
    Permissible AC ripple current can be determined by
    the following:
    I rms =
    =
    If two polar capacitors are connected back-to-back,
    (1)
    the pair may be operated on AC without need for DC
    bias. The first two criteria above must be observed. If DC
    is applied, the sum of DC and peak AC must not exceed,
    in either direction, the maximum working voltage specified
    for the ambient temperature.
    (1)
    Some KEMET Series provide convenient assemblies of
    non-polar pairs. The two negative terminals are connected
    internally. It is also permissible to connect the two positive
    terminals to form a non-polar pair.
    14. LONG-TERM STABILITY
    Within the general class of electrolytic capacitors,
    solid tantalum capacitors offer unusual stability of the three
    important parameters: capacitance, dissipation factor, and
    leakage current. These solid-state devices are not subject
    to the effects of electrolysis, deforming or drying-out asso-
    ciated with liquid-electrolyte capacitors.
    When stabilized for measurement at standard condi-
    tions, capacitance will typically change less than ±3% dur-
    ing a 10,000 hour life test +85° C. The same comparative
    change has been observed in shelf tests at +25° C extend-
    ing for 50,000 hours. (Some of this change may stem from
    instrument or fixture error.)
    Dissipation factor exhibits no typical trend. Data from
    10,000 hour life tests at +85° C show that initial limits (at
    standard conditions) are not exceeded at the conclusion of
    these tests.
    Leakage current is more variable than capacitance or
    DF; in fact, leakage current typically exhibits a logarithmic
    dependence in several respects. MIL-C-39003/1 permits
    leakage current (measured at standard conditions) to rise
    by a factor of four over 10,000 hour life tests. Typical
    behavior shows a lower rate of change, which may be
    negative or positive. Initial leakage currents are frequently
    so low (less than 0.1 nanoampere in the smallest CV
    capacitors, to about 10 microampere in the largest CV
    types) that changes of several orders of magnitude have
    no discernable effect on the usual circuit designs.
    15. FAILURE MODE
    Capacitor failure may be induced by exceeding the
    rated conditions of forward DC voltage, reverse DC volt-
    age, surge voltage, surge current, power dissipation, or
    temperature. As with any practical device, these capaci-
    tors also possess an inherent, although low, failure rate
    when operated within the rated condition.
    The dominant failure mode is by short-circuit. Minor
    parametric drifts (see Section 14 “Long-Term Stability”) are
    of no consequence in circuits suitable for solid tantalum
    capacitors. Catastrophic failure occurs as an avalanche in
    DC leakage current over a short (millisecond) time span.
    The failed capacitor, while called “short-circuited”, may
    exhibit a DC resistance of 10 to 104 ohm.
    If a failed capacitor is in an unprotected low-imped-
    ance circuit, continued flow of current through the capaci-
    tor may obviously produce severe overheating. This heat
    may melt the internal solder (all Series) and the sealing
    solder used in hermetic Series. The short-circuit failure
    may thereby be converted to an open-circuit failure. If the
    circuit does not open promptly, the over-heated capacitor
    may damage the circuit board or nearby components.
    Protection against such occurrence is obtained by current-
    limiting devices or fuses provided by the circuit design.
    Fortunately, the inherent failure rate of KEMET solid
    tantalum capacitors is low, and this failure rate may be fur-
    ther improved by circuit design. Statistical failure rates are
    provided for those capacitors with characters other than
    “A” in the next-to-last position of the part number. Relating
    circuit conditions to failure rate is aided by the guides in
    the section following.
    16. RELIABILITY PREDICTION
    Three important application conditions largely control
    failure rate: DC voltage, temperature, and circuit imped-
    ance. Estimates of the respective effects are provided by
    the nomograph in Figure 12 and Table 3 following. The
    nomograph related failure rate to voltage and temperature
    while the table relates failure rate to impedance. These
    estimates apply to steady-state DC conditions, and they
    assume usage within all other rated conditions.
    Standard conditions, which produce a unity failure
    rate factor, are rated voltage, +85° C, and 0.1 ohm-per-volt
    circuit impedance. While voltage and temperature are
    straightforward there is sometimes difficulty in determining
    impedance. What is required is the circuit impedance seen
    by the capacitor. If several capacitors are connected in
    parallel, the impedance seen by each is lowered by the
    source of energy stored in the other capacitors. Energy is
    similarly stored in series inductors.
    Failure rate is conventionally expressed in units of
    percent per thousand hours. As a sample calculation, sup-
    pose a particular batch of capacitors has a failure rate of
    0.5% Khr under standard conditions. What would be pre-
    dicted failure rate at 0.7 times rated voltage, +60° C and
    0.8
    /V The nomograph gives a factor of 7 x 10-4, and the
    table gives a factor of 0.3. The failure rate estimate is then:
    0.5 x 7 x10
    -4
    x 0.3 = 1.05 x 10
    -4
    , or 0.0001% Khr
    P(max)
    R
    KEMET
    APPLICATION NOTES FOR TANTALUM CAPACITORS
    T
    KEMET Electronics Corporation, P.O. Box 5928, Greenville, S.C. 29606 (864) 963-6300
    79
    P(max)
    R
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