參數(shù)資料
    型號: MAX14841EATA+T
    廠商: Maxim Integrated Products
    文件頁數(shù): 4/15頁
    文件大小: 0K
    描述: IC TXRX RS485 40MBPS 8TDFN
    產(chǎn)品培訓(xùn)模塊: Lead (SnPb) Finish for COTS
    Obsolescence Mitigation Program
    標(biāo)準(zhǔn)包裝: 1
    類型: 收發(fā)器
    驅(qū)動器/接收器數(shù): 1/1
    規(guī)程: RS485
    電源電壓: 3 V ~ 3.6 V
    安裝類型: 表面貼裝
    封裝/外殼: 8-WDFN 裸露焊盤
    供應(yīng)商設(shè)備封裝: 8-TDFN-EP(3x3)
    包裝: 標(biāo)準(zhǔn)包裝
    其它名稱: MAX14841EATA+TDKR
    12
    Maxim Integrated
    40Mbps, +3.3V, RS-485 Half-Duplex
    Transceivers
    MAX14840E/MAX14841E
    Detailed Description
    The MAX14840E/MAX14841E are +3.3V ESD-protected
    RS-485 transceivers intended for high-speed, half-duplex
    communications. A hot-swap capability eliminates false
    transitions on the bus during power-up or hot insertion.
    The MAX14840E features symmetrical fail-safe and larg-
    er receiver hysteresis, providing improved noise rejec-
    tion and improved recovered signals in high-speed and
    long cable applications. The MAX14841E has true fail-
    safe receiver inputs guaranteeing a logic-high receiver
    output when inputs are shorted or open. All devices have
    a 1-unit load receiver input impedance, allowing up to 32
    transceivers on the bus.
    The MAX14840E/MAX14841E transceivers draw 1.5mA
    (typ) supply current when unloaded or when fully loaded
    with the drivers disabled.
    Symmetrical Fail Safe (MAX14840E)
    At high data rates and with long cable lengths, the signal
    at the end of the cable is attenuated and distorted due to
    the lowpass characteristic of the transmission line. Under
    these conditions, fail-safe RS-485 receivers, which have
    offset threshold voltages, produce recovered signals
    with uneven mark-space ratios. The MAX14840E has
    symmetrical receiver thresholds, as shown in Figure 9.
    This produces near even mark-space ratios at the
    receiver’s output (RO). The MAX14840E also has higher
    receiver hysteresis than the MAX14841E and most other
    RS-485 transceivers. This results in higher receiver noise
    tolerance.
    Symmetrical fail safe means that the receiver’s output
    (RO) remains at the same logic state that it was before
    the differential input voltage VOD went to 0V. Under
    normal conditions, where UART signaling is used, this
    means that the state on the line prior to all drivers being
    disabled is a logic-high (i.e., a UART STOP bit).
    True Fail Safe (MAX14841E)
    The MAX14841E guarantees a logic-high receiver output
    when the receiver inputs are shorted or open or when
    they are connected to a terminated transmission line
    with all drivers disabled. This is the case if the receiver
    input threshold is between -10mV and -200mV. RO is
    logic-high if the differential receiver input voltage VOD is
    greater than or equal to -10mV.
    Hot-Swap Capability
    Hot-Swap Inputs
    When circuit boards are inserted into a hot or powered
    backplane, disturbances to the enable inputs and differ-
    ential receiver inputs can lead to data errors. Upon initial
    circuit board insertion, the processor undergoes its power-
    up sequence. During this period, the processor output
    drivers are high impedance and are unable to drive
    the DE and RE inputs of the MAX14840E/MAX14841E
    to a defined logic level. Leakage currents up to 10FA
    from the high-impedance output of a controller could
    cause DE and RE to drift to an incorrect logic state.
    Additionally, parasitic circuit board capacitance could
    cause coupling of VCC or GND to DE and RE. These
    factors could improperly enable the driver or receiver.
    However, the MAX14840E/MAX14841E have hot-swap
    inputs that avoid these potential problems.
    When VCC rises, an internal pulldown circuit holds DE
    low and RE high. After the initial power-up sequence,
    the pulldown circuit becomes transparent, resetting the
    hot-swap-tolerable inputs.
    Figure 9. Symmetrical Hysteresis
    RO
    -200mV
    +200mV
    VOD
    VTHP
    VTHF
    -10mV +10mV
    VTHP
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