參數(shù)資料
型號: TLV1548QDBREP
廠商: TEXAS INSTRUMENTS INC
元件分類: ADC
英文描述: 8-CH 10-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDSO20
封裝: GREEN, SSOP-20
文件頁數(shù): 34/35頁
文件大?。?/td> 686K
代理商: TLV1548QDBREP
TLV1548EP
LOW VOLTAGE 10BIT ANALOGTODIGITAL CONVERTER
WITH SERIAL CONTROL AND 8 ANALOG INPUTS
SGLS171A JUNE 2003 REVISED DECEMBER 2003
8
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
converter
The CMOS threshold detector in the successive-approximation conversion system determines the value of
each bit by examining the charge on a series of binary-weighted capacitors (see Figure 1). In the first phase
of the conversion process, the analog input is sampled by closing the SC switch and all ST switches
simultaneously. This action charges all of the capacitors to the input voltage.
In the next phase of the conversion process, all ST and SC switches are opened and the threshold detector
begins identifying bits by identifying the charge (voltage) on each capacitor relative to the reference (REF )
voltage. In the switching sequence, ten capacitors are examined separately until all ten bits are identified and
then the charge-convert sequence is repeated. In the first step of the conversion phase, the threshold detector
looks at the first capacitor (weight = 512). Node 512 of this capacitor is switched to the REF+ voltage, and the
equivalent nodes of all the other capacitors on the ladder are switched to REF . If the voltage at the summing
node is greater than the trip point of the threshold detector (approximately one-half VCC), a bit 0 is placed in the
output register and the 512-weight capacitor is switched to REF . If the voltage at the summing node is less
than the trip point of the threshold detector, a bit 1 is placed in the register and the 512-weight capacitor remains
connected to REF + through the remainder of the successive-approximation process. The process is repeated
for the 256-weight capacitor, the 128-weight capacitor, and so forth down the line until all bits are counted.
With each step of the successive-approximation process, the initial charge is redistributed among the
capacitors. The conversion process relies on charge redistribution to count and weigh the bits from MSB to LSB.
SC
Threshold
Detector
Node 512
REF
REF+
ST
512
VI
To Output
Latches
REF
ST
REF+
REF
ST
REF+
REF
ST
REF+
REF
ST
REF+
ST
REF+
REF
ST
REF+
REF
ST
1
2
4
8
128
256
REF
Figure 1. Simplified Model of the Successive-Approximation System
相關PDF資料
PDF描述
TLV1548QDBRQ1 8-CH 10-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDSO20
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TLV1549IDRG4 1-CH 10-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDSO8
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