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  • 參數(shù)資料
    型號(hào): LT3640EFE#TRPBF
    廠商: LINEAR TECHNOLOGY CORP
    元件分類: 穩(wěn)壓器
    英文描述: 3.4 A DUAL SWITCHING CONTROLLER, 2350 kHz SWITCHING FREQ-MAX, PDSO28
    封裝: 4.40 MM, LEAD FREE, PLASTIC, TSSOP-28
    文件頁(yè)數(shù): 7/24頁(yè)
    文件大?。?/td> 506K
    代理商: LT3640EFE#TRPBF
    LT3640
    3640f
    Output Capacitors and Output Ripple
    Theoutputcapacitorhastwoessentialfunctions.Insteady
    state, it determines the output voltage ripple. In transient,
    it stores energy in order to satisfy transient loads and
    stabilize the control loop. Ceramic capacitors have low
    equivalent series resistance (ESR) and provide the best
    ripple performance. A good starting value is:
    C
    V
    f
    OUT
    OUT S
    1
    150
    =
    where fS is in MHz, and COUT is the recommended output
    capacitance in F. Use X5R or X7R types. This choice will
    provide low output ripple and good transient response.
    A good starting value for the low voltage channel output
    capacitor is:
    C
    V
    f
    OUT
    S
    2
    100
    =
    In the case where VIN2 is connected to the high voltage
    channel output, the high voltage channel output capacitor
    can be used as the low voltage channel input capacitor.
    The required VIN2 input capacitor value is usually smaller
    than the high voltage output capacitor.
    Low ESR ceramic capacitors for VIN2 input and high volt-
    age channel output could form resonant tank and cause
    jitter in certain operating area. Avoid VIN2 input capacitor
    if possible.
    When choosing a capacitor, look carefully through the
    data sheet to find out what the actual capacitance is under
    operating conditions (applied voltage and temperature).
    A physically larger capacitor or one with a higher voltage
    rating may be required. High performance tantalum or
    electrolyticcapacitorscanbeusedfortheoutputcapacitor.
    Low ESR is important, so choose one that is intended for
    use in switching regulators. Table 3 lists several capacitor
    vendors.
    Table 3. Capacitor Vendors
    PART SERIES
    VENDOR
    Ceramic, Polymer, Tantalum
    Panasonic
    www.panasonic.com
    Ceramic, Tantalum
    Kemet
    www.kemet.com
    Ceramic, Polymer, Tantalum
    Sanyo
    www.sanyovideo.com
    Ceramic
    Murata
    www.murata.com
    Ceramic, Tantalum
    AVX
    www.avxcorp.com
    Ceramic
    Taiyo Yuden
    www.taiyo-yuden.com
    Catch Diode
    The high voltage channel requires an external catch diode
    toconductcurrentduringswitchoff-time.Averageforward
    current in normal operation can be calculated from:
    I
    V
    D AVG
    OUT
    IN
    OUT
    IN
    (
    )
    (
    )
    =
    where IOUT is the output load current. Use a 1A or 2A
    rated Schottky diode. Peak reverse voltage is equal to the
    regulator input voltage. Use a diode with a reverse voltage
    rating greater than the input voltage. Table 4 lists several
    Schottky diodes and their manufacturers.
    Table 4. Diode Vendors
    PART NUMBER
    VR
    (V)
    IAVE
    (A)
    VF AT 1A
    (MV)
    VF AT 2A
    (MV)
    On Semiconductor
    MBRM120E
    MBRM140
    20
    40
    1
    530
    595
    Diodes Inc.
    B120
    B130
    B220
    B230
    DFLS240L
    20
    30
    20
    30
    40
    1
    2
    500
    International Rectifier
    10BQ030
    20BQ030
    30
    1
    2
    420
    470
    applicaTions inForMaTion
    相關(guān)PDF資料
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    LT3640IFE#TRPBF 3.4 A DUAL SWITCHING CONTROLLER, 2350 kHz SWITCHING FREQ-MAX, PDSO28
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