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參數(shù)資料
| 型號： | ADS809 |
| 英文描述： | 12-Bit, 80MHz Sampling ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 12位，80MHz的采樣模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 9/20頁 |
| 文件大?。?/td> | 437K |
| 代理商： | ADS809 |
ADS809
SBAS170C
9
www.ti.com
APPLICATION INFORMATION
THEORY OF OPERATION
The ADS809 is a high-speed, high performance, CMOS
ADC built with a fully differential, 9-stage pipeline architec-
ture. Each stage contains a low-resolution quantizer and
digital error correction logic, ensuring excellent differential
linearity and no missing codes at the 12-bit level. The conver-
sion process is initiated by a rising edge of the external
convert clock. Once the signal is captured by the input track-
and-hold amplifier, the bits are sequentially encoded starting
with the Most Significant Bit (MSB). This process results in a
data latency of five clock cycles, after which the output data
is available as a 12-bit parallel word either coded in a straight
binary or binary two
’
s complement format.
The analog input of the ADS809 consists of a differential
track-and-hold circuit, as shown in Figure 1. The differential
topology produces a high level of AC-performance at high
sampling rates. It also results in a very high usable input
bandwidth that is especially important for IF, or undersampling
applications. Both inputs (IN,
IN
) require external biasing up
to a common-mode voltage that is typically at the mid-supply
level (+V
S
/2). This is because the on-resistance of the CMOS
switches is lowest at this voltage, minimizing the effects of
the signal dependent nonlinearity of R
ON
. The track-and-hold
circuit can also convert a single-ended input signal into a fully
differential signal for the quantizer. For ease of use, the
ADS809 incorporates a selectable voltage reference, a ver-
satile clock input, and a logic output driver designed to
interface to 3V or 5V logic.
particularly suited for communication systems that digitize
wideband signals. Features on the ADS809, like the input
range selector or the option of an external reference, provide
the needed flexibility to accommodate a wide range of
applications. In any case, the analog interface/driver require-
ments should be carefully examined before selecting the
appropriate circuit configuration. The circuit definition should
include considerations on the input frequency spectrum and
amplitude, single-ended versus differential driver configura-
tion, as well as the available power supplies.
Differential versus Single-Ended
The ADS809 input structure allows it to be driven either
single-ended or differentially. Differential operation of the
ADS809 requires an input signal that consists of an in-phase
and a 180
°
out-of-phase component simultaneously applied
to the inputs (IN,
IN
). Differential signals offer a number of
advantages that, in many applications, will be instrumental in
achieving the best harmonic performance of the ADS809:
The signal amplitude is half of that required for the single-
ended operation, and is therefore less demanding to achieve
while maintaining good linearity performance from the signal
source.
The reduced signal swing allows for more headroom of the
interface circuitry, and therefore a wider selection of the
best suitable driver amplifier.
Even-order harmonics are minimized.
Improves the noise immunity based on the converter
’
s
common-mode input rejection.
For the single-ended mode, the signal is applied to one of the
inputs while the other input is biased with a DC voltage to the
required common-mode level. Both inputs are identical in
terms of their impedance and performance except that apply-
ing the signal to the complementary input (
IN
) instead of the
IN-input will invert the orientation of the input signal relative
to the output code. For example, if the input driver operates
in inverting mode, using
IN
as the signal input, it will restore
the phase of the signal to its original orientation. Time-
domain applications may benefit from a single-ended inter-
face configuration and a reduced circuit complexity. Driving
the ADS809 with a single-ended signal will result in a trade-
off of the excellent distortion performance, while maintaining
a good SNR. The trade-off of the differential input configura-
tion over the single-ended is its increase in circuit complexity.
In either case, the selection of the driver amplifier should be
such that the amplifier
’
s performance will not degrade the
ADC
’
s performance.
Input Full-Scale Range versus Performance
Employing dual-supply amplifiers and AC-coupling will usually
yield the best results. DC-coupling and/or single-supply ampli-
fiers impose additional design constrains due to their head-
room requirements, especially when selecting the 2Vp-p input
range. The full-scale input range of the ADS809 is defined
either by the settings of the reference select pins (SEL1,
SEL2) or by an external reference voltage (see Table I).
T&H
C
IN
C
IN
S
1
S
2
S
3
S
4
S
6
S
5
IN
IN
Tracking Phase: S
1
, S
2
, S
3
, S
4
Closed; S
5
, S
6
Open
Hold Phase: S
1
, S
2
, S
3
, S
4
Open; S
5
, S
6
Closed
ADS809
FIGURE 1. Simplified Circuit of Input Track-and-Hold Amplifier.
DRIVING THE ANALOG INPUTS
Types of Applications
The analog input of the ADS809 can be configured in various
ways and driven with different circuits, depending on the
application and the desired level of performance. Offering a
high dynamic range at high input frequencies, the ADS809 is
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS809Y/250 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 80MHz Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS809Y/250G4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 80MHz Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS809Y/2K | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 80MHz Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS809Y/2K5 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:A/D CONVERTER |
| ADS809Y/2KG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 80MHz Sampling ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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