參數(shù)資料
型號(hào): LTC2486IDE
廠商: LINEAR TECHNOLOGY CORP
元件分類: ADC
英文描述: 16-Bit 2-/4-Channel ツヒ ADC with PGA and Easy Drive Input Current Cancellation
中文描述: 4-CH 16-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PQCC14
封裝: 4 X 3 MM, PLASTIC, MO-229WGED-3, QFN-14
文件頁數(shù): 34/36頁
文件大?。?/td> 596K
代理商: LTC2486IDE
LTC2486
34
2486f
APPLICATIONS INFORMATION
Easy Drive ADCs Simplify Measurement of High
Impedance Sensors
Delta-Sigma ADCs, with their high accuracy and high noise
immunity, are ideal for directly measuring many types
of sensors. Nevertheless, input sampling currents can
overwhelm high source impedances or low-bandwidth,
micropower signal conditioning circuits. The LTC2486
solves this problem by balancing the input currents, thus
simplifying or eliminating the need for signal conditioning
circuits.
A common application for a delta-sigma ADC is thermistor
measurement. Figure 38 shows two examples of thermistor
digitization benefiting from the Easy Drive technology.
The first circuit (applied to input channels CH0 and CH1)
uses balanced reference resistors in order to balance the
common mode input/reference voltage and balance the
differential input source resistance. If reference resistors
R1 and R4 are exactly equal, the input current is zero and
no errors result. If these resistors have a 1% tolerance,
the maximum error in measured resistance is 1.6
Ω
due
to a shift in common mode voltage; far less than the 1%
error of the reference resistors themselves. No amplifier
is required, making this an ideal solution in micropower
applications.
Easy Drive also enables very low power, low bandwidth
amplifiers to drive the input to the LTC2486. As shown
in Figure 38, CH2 is driven by the LT1494. The LT1494
has excellent DC specs for an amplifier with 1.5μA supply
current (the maximum offset voltage is 150μV and the
open loop gain is 100,000). Its 2kHz bandwidth makes
it unsuitable for driving conventional delta sigma ADCs.
Adding a 1k
Ω
, 0.1μF filter solves this problem by providing
a charge reservoir that supplies the LTC2486 instantaneous
current, while the 1k resistor isolates the capacitive load
from the LT1494.
Conventional delta sigma ADCs input sampling current
lead to DC errors as a result of incomplete settling in the
external RC network.
The Easy Drive technology cancels the differential input
current. By balancing the negative input (CH3) with a 1k
Ω
,
0.1μF network errors due to the common mode input
current are cancelled.
相關(guān)PDF資料
PDF描述
LTC2487 16-Bit 2-/4-Channel ADC with PGA, Easy Drive and I2C Interface
LTC2487CDEPBF 16-Bit 2-/4-Channel ADC with PGA, Easy Drive and I2C Interface
LTC2487CDETRPBF 16-Bit 2-/4-Channel ADC with PGA, Easy Drive and I2C Interface
LTC2487IDEPBF 16-Bit 2-/4-Channel ADC with PGA, Easy Drive and I2C Interface
LTC2487IDETRPBF 16-Bit 2-/4-Channel ADC with PGA, Easy Drive and I2C Interface
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