参数资料
| 型号： | AD9444BSVZ-80 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 14/40页 |
| 文件大小： | 0K |
| 描述： | IC ADC 14BIT 80MSPS 100TQFP |
| 标准包装： | 1 |
| 位数： | 14 |
| 采样率（每秒）： | 80M |
| 数据接口： | 并联 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 1.4W |
| 电压电源： | 单电源 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 100-TQFP 裸露焊盘 |
| 供应商设备封装： | 100-TQFP-EP（14x14） |
| 包装： | 托盘 |
| 输入数目和类型： | 1 个差分，单极 |
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AD9444
Rev. 0 | Page 21 of 40
Table 9. Reference Configuration Summary
Selected Mode
SENSE Voltage
Resulting VREF (V)
Resulting Differential Span (V p-p)
External Reference
AVDD
N/A
2 × External Reference
Internal Fixed Reference
VREF
0.5
1.0
Programmable Reference
0.2 V to VREF
+
×
R1
R2
1
0.5
(See Figure 41)
2 × VREF
Internal Fixed Reference
AGND to 0.2 V
1.0
2.0
External Reference Operation
The AD9444’s internal reference is trimmed to enhance the gain
accuracy of the ADC. An external reference may be more stable
over temperature, but the gain of the ADC is not likely to be
improved. Figure 36 shows the typical drift characteristics of the
internal reference in both 1 V and 0.5 V modes.
When the SENSE pin is tied to AVDD, the internal reference is
disabled, allowing the use of an external reference. An internal
reference buffer loads the external reference with an equivalent
7 k load. The internal buffer still generates the positive and
negative full-scale references, REFT and REFB, for the ADC
core. The input span is always twice the value of the reference
voltage; therefore, the external reference must be limited to a
maximum of 1 V.
Analog Inputs
As with most new high speed, high dynamic range ADCs, the
analog input to the AD9444 is differential. Differential inputs
improve on-chip performance as signals are processed through
attenuation and gain stages. Most of the improvement is a result
of differential analog stages having high rejection of even-order
harmonics. There are also benefits at the PCB level. First,
differential inputs have high common-mode rejection of stray
signals, such as ground and power noise. Second, they provide
good rejection of common-mode signals, such as local oscillator
feedthrough. The specified noise and distortion of the AD9444
cannot be realized with a single-ended analog input, so such
configurations are discouraged. Contact ADI for recommenda-
tions of other 14-bit ADCs that support single-ended analog
input configurations.
With the 1 V reference (nominal value, see the Internal Refer-
ence Trim section), the differential input range of the AD9444’s
analog input is nominally 2 V p-p or 1 V p-p on each input
(VIN+ or VIN).
3.5V
VIN+
VIN–
1Vp-p
DIGITAL OUT = ALL 1s
DIGITAL OUT = ALL 0s
05089-045
Figure 42. Differential Analog Input Range for VREF = 1 V
The AD9444 analog input voltage range is offset from ground
by 3.5 V. Each analog input connects through a 1 k resistor to
the 3.5 V bias voltage and to the input of a differential buffer.
The internal bias network on the input properly biases the
buffer for maximum linearity and range (see the Equivalent
Circuits section). Therefore, the analog source driving the
AD9444 should be ac-coupled to the input pins. The recom-
mended method for driving the analog input of the AD9444 is
to use an RF transformer to convert single-ended signals to
differential (see Figure 44). Series resistors between the output
of the transformer and the AD9444 analog inputs help isolate
the analog input source from switching transients caused by the
internal sample-and-hold circuit. The series resistors, along with
the 1 k resisters connected to the internal 3.5 V bias, must be
considered in impedance matching the transformers input. For
example, if RT were set to 51 and RS were set to 33 , along
with a 1:1 impedance ratio transformer, the input would match
a 50 source with a full-scale drive of 10.0 dBm. The 50
impedance matching can also be incorporated on the secondary
side of the transformer, as shown in the evaluation board sche-
matic (see Figure 47 and Figure 59).
05089-046
0.1
F
RT
AD9444
AIN
RS
ADT1–1WT
ANALOG
INPUT
SIGNAL
Figure 43. Transformer-Coupled Analog Input Circuit
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD9444-CMOS/PCB | 制造商:Analog Devices 功能描述:Evaluation Kit For 14-Bit, 80 MSPS, A/D Converter |
| AD9444-CMOSPCB | 制造商:AD 制造商全称:Analog Devices 功能描述:High Speed ADC USB FIFO Evaluation Kit |
| AD9444-LVDS/PCB | 制造商:Analog Devices 功能描述:14-BIT, 80 MSPS ADC PB FREE EVAL BD. - Trays |
| AD9444-LVDS/PCBZ | 制造商:Analog Devices 功能描述:LVDS Mode Evaluation Board 制造商:Analog Devices 功能描述:14-BIT, 80 MSPS ADC EVAL BD. - Bulk |
| AD9444-LVDSPCB | 制造商:AD 制造商全称:Analog Devices 功能描述:High Speed ADC USB FIFO Evaluation Kit |
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