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    參數(shù)資料
    型號: DS1878T+T
    廠商: Maxim Integrated Products
    文件頁數(shù): 9/101頁
    文件大?。?/td> 0K
    描述: IC CTLR SFP W/DGTL LDD RX 28TQFN
    產(chǎn)品培訓模塊: Lead (SnPb) Finish for COTS
    Obsolescence Mitigation Program
    標準包裝: 2,500
    類型: SFP+ 控制器
    輸入類型: 模擬,數(shù)字
    輸出類型: 數(shù)字
    接口: I²C,LDD,串行
    電流 - 電源: 2.5mA
    安裝類型: 表面貼裝
    封裝/外殼: 28-WFQFN 裸露焊盤
    供應商設備封裝: 28-TQFN-EP(5x5)
    包裝: 帶卷 (TR)
    temperature, so the tINIT time is not required for the device
    to recall the APC and MOD set points from EEPROM.
    BIAS and MODULATION Registers as a
    Function of Transmit Disable (TXD)
    If TXD is asserted (logic 1) during normal operation,
    the 3-wire master writes the laser driver bias and
    MODULATION DACs to 0. When TXD is deasserted
    (logic 0), the device sets the MODULATION register
    with the value associated with the present temperature,
    and initializes the BIAS register using the same search
    algorithm as done at startup. When asserted, soft TXD
    (TXDC) (Lower Memory, Register 6Eh) would allow a
    software control identical to the TXD pin (see Figure 3).
    APC and Quick-Trip Timing
    As shown in Figure 4, the device’s input comparator is
    shared between the APC control loop and the quick-
    trip alarms (TXP HI, TXP LO, LOS, BIAS HI, and IBIAS
    MAX). The comparator polls the alarms in a multiplexed
    sequence. Five of every eight comparator readings are
    used for APC loop bias-current control. The other three
    updates are used to check the HTXP/LTXP (monitor
    diode voltage), the HBATH (MON1), and LOS (MON3)
    signals against the internal APC, BIAS, and MON3 ref-
    erence, respectively. If the last APC comparison was
    higher than the APC set point, it makes an HTXP com-
    parison, and if it is lower, it makes an LTXP compari-
    son. Depending on the results of the comparison, the
    corresponding alarms and warnings (TXP HI, TXP LO)
    are asserted or deasserted.
    The device has a programmable comparator sample
    time based on an internally generated clock to facilitate
    a wide variety of external filtering options and time
    delays resulting from writing values to the laser driver’s
    bias DAC. The SAMPLE RATE register (Table 02h,
    Register 88h) determines the sampling time. Samples
    occur at a regular interval, tREP. Table 2 shows the
    sample rate options available. Any quick-trip alarm that
    is detected by default remains active until a subse-
    quent comparator sample shows the condition no
    longer exists. A second bias current monitor (BIAS
    MAX) compares a Maxim laser driver’s BIAS DAC’s
    code to a digital value stored in the IBIASMAX register.
    This comparison is made at every bias current update
    to ensure that a high-bias current is quickly detected.
    DS1878
    SFP+ Controller with Digital LDD Interface
    ______________________________________________________________________________________
    15
    APC QUICK-TRIP SAMPLE TIMES
    HBIAS
    SAMPLE
    HBIAS
    SAMPLE
    LOS
    SAMPLE
    APC
    SAMPLE
    APC
    SAMPLE
    APC
    SAMPLE
    APC
    SAMPLE
    APC
    SAMPLE
    APC
    SAMPLE
    HTXP/LTXP
    SAMPLE
    tREP
    Figure 4. APC Loop and Quick-Trip Sample Timing
    Table 2. Update Rate Timing
    APC_SR[2:0]
    SAMPLE PERIOD (tREP)
    (ns)
    000b
    800
    001b
    1200
    010b
    1600
    011b
    2000
    100b
    2800
    101b
    3200
    110b
    4400
    111b
    6400
    tOFF
    tON
    TXD
    TXDOUT
    Figure 3. TXD Timing
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