1. 參數資料
    型號: RT9167A-39CB
    廠商: Electronic Theatre Controls, Inc.
    元件分類: 基準電壓源/電流源
    英文描述: LOW NOISE FIXED OUTPUT VOLTAGE 200MA/500MA LDO REGULATOR
    中文描述: 低噪聲固定輸出電壓200MA/500MA LDO穩(wěn)壓器
    文件頁數: 8/14頁
    文件大?。?/td> 257K
    代理商: RT9167A-39CB
    RT9167/A
    www.richtek-ic.com.tw
    8
    DS9167/A-10 July 2001
    Applications Guides
    Capacitor Selection and Regulator Stability
    Like any low-dropout regulator, the external capacitors
    used with the RT9167/A must be carefully selected for
    regulator stability and performance.
    Using a capacitor whose value is > 1
    μ
    F on the
    RT9167/A input and the amount of capacitance can be
    increased without limit. The input capacitor must be
    located a distance of not more than 0.5" from the input
    pin of the IC and returned to a clean analog ground.
    Any good quality ceramic or tantalum can be used for
    this capacitor. The capacitor with larger value and
    lower ESR (equivalent series resistance) provides
    better PSRR and line-transient response.
    The output capacitor must meet both requirements for
    minimum amount of capacitance and ESR in all LDOs
    application. The RT9167/A is designed specifically to
    work with low ESR ceramic output capacitor in space-
    saving and performance consideration. Using a
    ceramic capacitor whose value is at least 1uF with
    ESR is > 5m
    on the RT9167/A output ensures
    stability. The RT9167/A still works well with output
    capacitor of other types due to the wide stable ESR
    range. Fig.1 shows the curves of allowable ESR range
    as a function of load current for various output
    voltages and capacitor values. Output capacitor of
    larger capacitance can reduce noise and improve
    load-transient response, stability, and PSRR. The
    output capacitor should be located not more than
    0.5" from the V
    OUT
    pin of the RT9167/A and returned
    to a clean analog ground.
    Note that some ceramic dielectrics exhibit large
    capacitance and ESR variation with temperature. It
    may be necessary to use 2.2
    μ
    F or more to ensure
    stability at temperatures below -10°C in this case. Also,
    tantalum capacitors, 2.2
    μ
    F or more may be needed to
    maintain capacitance and ESR in the stable region for
    strict application environment.
    Tantalum capacitors maybe suffer failure due to surge
    current when it is connected to a low-impedance
    source of power (like a battery or very large capacitor).
    If a tantalum capacitor is used at the input, it must be
    guaranteed to have a surge current rating sufficient for
    the application by the manufacture.
    Use a 10nF bypass capacitor at BP for low output
    voltage noise. The capacitor, in conjunction with an
    internal 200K
    resistor, which connects bypass pin
    and the band-gap reference, creates an 80Hz low-
    pass filter for noise reduction. Increasing the
    capacitance will slightly decrease the output noise,
    but increase the start-up time. The capacitor
    connected to the bypass pin for noise reduction must
    have very low leakage. This capacitor leakage
    current causes the output voltage to decline by a
    proportional amount to the current due to the voltage
    drop on the internal 200K
    resistor. Fig. 2 shows the
    power on response.
    Fig. 1
    C
    OUT
    = 4.7
    μ
    F
    C
    OUT
    = 1
    μ
    F
    C
    O
    Region of Stable C
    OUT
    ESR vs. Load Current
    100
    0 40 80 120 160 200
    Load Current (mA)
    0.001
    0.01
    0.1
    1
    10
    (
    )
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