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  • 參數(shù)資料
    型號: MAX1241ACPA
    廠商: MAXIM INTEGRATED PRODUCTS INC
    元件分類: ADC
    英文描述: HDMI Hider 40-VQFN 0 to 70
    中文描述: 1-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDIP8
    封裝: ROHS COMPLIANT, PLASTIC, DIP-8
    文件頁數(shù): 8/16頁
    文件大小: 280K
    代理商: MAX1241ACPA
    M
    +2.7V, Low-Power,
    12-Bit S erial ADCs in 8-Pin S O
    8
    _______________________________________________________________________________________
    _______________Detailed Description
    Converter Operation
    The MAX1240/MAX1241 use an input track/hold (T/H)
    and successive-approximation register (SAR) circuitry
    to convert an analog input signal to a digital 12-bit out-
    put. No external-hold capacitor is needed for the T/H.
    Figure 3 shows the MAX1240/MAX1241 in its simplest
    configuration. The MAX1240/MAX1241 convert input
    signals in the 0V to V
    REF
    range in 9μs, including T/H
    acquisition time. The MAX1240’s internal reference is
    trimmed to 2.5V, while the MAX1241 requires an external
    reference. Both devices accept voltages from 1.0V to
    V
    DD
    . The serial interface requires only three digital lines
    (SCLK,
    CS
    ,
    and DOUT) and provides an easy interface
    to microprocessors (μPs).
    The MAX1240/MAX1241 have two modes: normal and
    shutdown. Pulling
    SHDN
    low shuts the device down and
    reduces supply current below 10μA (V
    DD
    3.6V
    )
    , while
    pulling
    SHDN
    high or leaving it open puts the device
    into operational mode. Pulling
    CS
    low initiates a conver-
    sion. The conversion result is available at DOUT in
    unipolar serial format. The serial data stream consists
    of a high bit, signaling the end of conversion (EOC), fol-
    lowed by the data bits (MSB first).
    Analog Input
    Figure 4 illustrates the sampling architecture of the ana-
    log-to-digital converter’s (ADC’s) comparator. The full-
    scale input voltage is set by the voltage at REF.
    Track/Hold
    In track mode, the analog signal is acquired and stored
    in the internal hold capacitor. In hold mode, the T/H
    switch opens and maintains a constant input to the
    ADC’s SAR section.
    During acquisition, the analog input (AIN) charges
    capacitor C
    HOLD
    . Bringing
    CS
    low ends the acquisition
    interval. At this instant, the T/H switches the input side
    of C
    HOLD
    to GND. The retained charge on C
    HOLD
    repre-
    sents a sample of the input, unbalancing node ZERO at
    the comparator’s input.
    In hold mode, the capacitive digital-to-analog converter
    (DAC) adjusts during the remainder of the conversion
    cycle to restore node ZERO to 0V within the limits of 12-
    bit resolution. This action is equivalent to transferring a
    charge from C
    HOLD
    to the binary-weighted capacitive
    DAC, which in turn forms a digital representation of the
    analog input signal. At the conversion’s end, the input
    side of C
    HOLD
    switches back to AIN, and C
    HOLD
    charges to the input signal again.
    The time required for the T/H to acquire an input signal
    is a function of how quickly its input capacitance is
    charged. If the input signal’s source impedance is high,
    the acquisition time lengthens and more time must be
    allowed between conversions. The acquisition time
    (t
    ACQ
    ) is the maximum time the device takes to acquire
    the signal, and is also the minimum time needed for the
    signal to be acquired. Acquisition time is calculated by:
    t
    ACQ
    = 9(R
    S
    + R
    IN
    ) x 16pF
    where R
    IN
    = 9k
    , R
    S
    = the input signal’s source imped-
    ance, and t
    ACQ
    is never less than 1.5μs. Source imped-
    ances below 1k
    do not significantly affect the ADC’s
    AC performance.
    AIN
    TRACKINPUT
    HOLD
    GND
    TRACK
    HOLD
    9k
    R
    IN
    C
    HOLD
    16pF
    -
    +
    C
    SWITCH
    COMPARATOR
    ZERO
    REF
    12-BIT CAPACITIVE DAC
    AT THE SAMPLING INSTANT,
    THE INPUT SWITCHES FROM
    AIN TOGND.
    SHUTDOWN
    INPUT
    ANALOG INPUT
    0V TOV
    REF
    +2.7V to +3.6V*
    *
    **
    V
    DD,MAX
    = +5.25V (MAX1241)
    4.7
    μ
    F (MAX1240)
    0.1
    μ
    F (MAX1241)
    1
    2
    3
    4
    V
    DD
    AIN
    SHDN
    REF
    8
    7
    6
    5
    SCLK
    CS
    DOUT
    GND
    SERIAL
    INTERFACE
    C**
    4.7
    μ
    F
    0.1
    μ
    F
    REFERENCE
    INPUT
    (MAX1241 ONLY)
    MAX1240
    MAX1241
    Figure 3. Operational Diagram
    Figure 4. Equivalent Input Circuit
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    相關代理商/技術參數(shù)
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