參數(shù)資料
型號(hào): ADS1601IPFBR
元件分類(lèi): ADC
英文描述: 16-BIT 1.25MSPS ANALOG TO DIGITAL CONVERTER
中文描述: 16位1.25MSPS時(shí)模數(shù)轉(zhuǎn)換器
文件頁(yè)數(shù): 16/26頁(yè)
文件大?。?/td> 386K
代理商: ADS1601IPFBR
SBAS322 DECEMBER 2004
www.ti.com
16
INPUT CIRCUITRY
The ADS1601 uses switched-capacitor circuitry to measure
the input voltage. Internal capacitors are charged by the
inputs and then discharged internally with this cycle
repeating at the frequency of CLK. Figure 36 shows a
conceptual diagram of these circuits. Switches S2 represent
the net effect of the modulator circuitry in discharging the
sampling capacitors; the actual implementation is different.
The timing for switches S1 and S2 is shown in Figure 37.
S
1
S
2
10pF
AINP
ADS1601
8pF
VMID
S
1
S
2
10pF
AINN
8pF
VMID
AGND
Figure 36. Conceptual Diagram of Internal
Circuitry Connected to the Analog Inputs
On
S1
S2
Off
On
Off
t
SAMPLE
= 1/f
CLK
Figure 37. Timing for the Switches in Figure 36
DRIVING THE INPUTS
The external circuits driving the ADS1601 inputs must be
able to handle the load presented by the switching capacitors
within the ADS1601. The input switches S1 in Figure 36 are
closed for approximately one-half of the sampling period,
t
sample
, allowing only
24ns for the internal capacitors to be
charged by the inputs when f
CLK
= 20MHz.
Figure 38 and Figure 39 show the recommended circuits
when using single-ended or differential op amps,
respectively.
The analog inputs must be driven
differentially to achieve optimum performance.
The
external capacitors, between the inputs and from each
input to AGND, improve linearity and should be placed as
close to the pins as possible. Place the drivers close to the
inputs and use good capacitor bypass techniques on their
supplies, such as a smaller high-quality ceramic capacitor
in parallel with a larger capacitor. Keep the resistances
used in the driver circuits low—thermal noise in the driver
circuits degrades the overall noise performance. When the
signal can be ac-coupled to the ADS1601 inputs, a simple
RC filter can set the input common-mode voltage. The
ADS1601 is a high-speed, high-performance ADC.
Special care must be taken when selecting the test
equipment and setup used with this device. Pay particular
attention to the signal sources to ensure they do not limit
performance when measuring the ADS1601.
392
OPA2822
ADS1601
AGND
OPA2822
40pF
V
CM(1)
V
CM(1)
V
CM(1)
100pF
AINP
AINN
100pF
(3)
392
40pF
100pF
(1) Recommended V
= 2.7V.
(2) Optional accoupling circuit provides commonmode input voltage.
(3) Increase to 390pF when f
IN
100kHz for improved SNR and THD.
(2)
(2)
(2)
(2)
V
IN
2
V
IN
2
392
392
392
0.01
μ
F
0.01
μ
F
392
1
μ
F
392
1k
1k
1
μ
F
392
49.9
49.9
Figure 38. Recommended Driver Circuit Using the
OPA2822
ADS1601
THS4503
22pF
V
IN
+V
IN
100pF
100pF
AINP
AINN
100pF
24.9
392
392
24.9
392
392
22pF
V
CM
Figure 39. Recommended Driver Circuit Using the
THS4503 Differential Amplifier
相關(guān)PDF資料
PDF描述
ADS1601IPFBT 16-BIT 1.25MSPS ANALOG TO DIGITAL CONVERTER
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ADS1602IPFBRG4 16-Bit, 2.5MSPS Analog-to-Digital Converter
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ADS1602EVM 功能描述:數(shù)據(jù)轉(zhuǎn)換 IC 開(kāi)發(fā)工具 ADS1602EVM Eval Mod RoHS:否 制造商:Texas Instruments 產(chǎn)品:Demonstration Kits 類(lèi)型:ADC 工具用于評(píng)估:ADS130E08 接口類(lèi)型:SPI 工作電源電壓:- 6 V to + 6 V
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