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| 型号： | AD9225ARSRL |
| 厂商： | Analog Devices Inc |
| 文件页数： | 8/25页 |
| 文件大小： | 0K |
| 描述： | IC ADC 12BIT 25MSPS 28-SSOP |
| 标准包装： | 1,500 |
| 位数： | 12 |
| 采样率（每秒）： | 25M |
| 数据接口： | 并联 |
| 转换器数目： | 7 |
| 功率耗散（最大）： | 373mW |
| 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： | 28-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 28-SSOP |
| 包装： | 带卷 (TR) |
| 输入数目和类型： | 2 个单端，双极；1 个差分，单极 |
–16–
AD9225
REFERENCE CONFIGURATIONS
The figures associated with this section on internal and external
reference operation do not show recommended matching series
resistors for VINA and VINB for the purpose of simplicity. Refer
to the Driving the Analog Inputs and Introduction sections for a
discussion of this topic. The figures do not show the decoupling
network associated with the CAPT and CAPB pins. Refer to the
Reference Operation section for a discussion of the internal refer-
ence circuitry and the recommended decoupling network shown
in Figure 16.
USING THE INTERNAL REFERENCE
Single-Ended Input with 0 to 2 3 VREF Range
Figure 16 shows how to connect the AD9225 for a 0 V to 2 V or
0 V to 4 V input range via pin strapping the SENSE pin. An inter-
mediate input range of 0 to 2
VREF can be established using the
resistor programmable configuration in Figure 19.
In either case, both the midscale voltage and input span are directly
dependent on the value of VREF. More specifically, the midscale
voltage is equal to VREF while the input span is equal to 2
VREF.
Thus, the valid input range extends from 0 to 2
VREF. When
VINA is
0 V, the digital output will be 0x000; when VINA is
≥ 2 VREF, the digital output will be 0xFFF.
Shorting the VREF pin directly to the SENSE pin places the inter-
nal reference amplifier in unity-gain mode and the resulting VREF
output is 1 V. Therefore, the valid input range is 0 V to 2 V.
However, shorting the SENSE pin directly to the REFCOM pin
configures the internal reference amplifier for a gain of 2.0 and the
resulting VREF output is 2.0 V. Therefore, the valid input range
becomes 0 V to 4 V. The VREF pin should be bypassed to the
REFCOM pin with a 10
mF tantalum capacitor in parallel with a
low inductance 0.1
mF ceramic capacitor.
10 F
VINA
VREF
AD9225
0.1 F
VINB
2
VREF
0V
SHORT FOR 0V TO 2V
INPUT SPAN
SENSE
SHORT FOR 0V TO 4V
INPUT SPAN
REFCOM
Figure 17. Internal Reference—2 V p-p Input Span,
VCM = 1 V, or 4 V p-p Input Span
Figure 18 shows the single-ended configuration that gives good
dynamic performance (SINAD, SFDR). To optimize dynamic
specifications, center the common-mode voltage of the analog
input at approximately by 2.5 V by connecting VINB to a low
impedance 2.5 V source. As described above, shorting the VREF
pin directly to the SENSE pin results in a 1 V reference voltage
and a 2 V p-p input span. The valid range for input signals is 1.5 V
to 3.5 V. The VREF pin should be bypassed to the REFCOM pin
with a 10
mF tantalum capacitor in parallel with a low-inductance
0.1
mF ceramic capacitor.
This reference configuration could also be used for a differential
input in which VINA and VINB are driven via a transformer as
shown in Figure 13. In this case, the common-mode voltage,
VCM , is set at midsupply by connecting the transformer’s center
tap to CML of the AD9225. VREF can be configured for 1.0 V
or 2.0 V by connecting SENSE to either VREF or REFCOM,
respectively. Note that the valid input range for each of the differ-
ential inputs is one half of the single-ended input and thus becomes
VCM – VREF/2 to VCM + VREF/2.
1V
0.1 F
10 F
VINA
VINB
VREF
SENSE
REFCOM
AD9225
3.5V
1.5V
VCM
Figure 18. Internal Reference—2 V p-p Input Span,
VCM = 2.5 V
Resistor Programmable Reference
Figure 19 shows an example of how to generate a reference voltage
other than 1.0 V or 2.0 V with the addition of two external resistors
and a bypass capacitor. Use the equation
VREF = 1 V
(1 + R1/R2)
to determine appropriate values for R1 and R2. These resistors
should be in the 2 k
W to 100 kW range. For the example shown,
R1 equals 2.5 k
W and R2 equals 5 kW. From the equation above,
the resultant reference voltage on the VREF pin is 1.5 V. This
sets the input span to be 3 V p-p. To assure stability, place a 0.1
mF
ceramic capacitor in parallel with R1.
The midscale voltage can be set to VREF by connecting VINB to
VREF to provide an input span of 0 to 2
VREF. Alternatively,
the midscale voltage can be set to 2.5 V by connecting VINB to a
low impedance 2.5 V source. For the example shown, the valid
input single-ended range for VINA is 1 V to 4 V since VINB is set
to an external, low impedance 2.5 V source. The VREF pin should
be bypassed to the REFCOM pin with a 10
mF tantalum capacitor
in parallel with a low inductance 0.1
mF ceramic capacitor.
1.5V
C1
0.1 F
10 F
VINA
VINB
VREF
SENSE
REFCOM
AD9225
4V
1V
2.5V
R1
2.5k
R2
5k
0.1 F
Figure 19. Resistor Programmable Reference
3 V p-p Input Span, VCM = 2.5 V
Rev. C
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD9225ARSZ | 功能描述:IC ADC 12BIT 25MSPS 28-SSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1 系列:microPOWER™ 位数:8 采样率（每秒）:1M 数据接口:串行，SPI? 转换器数目:1 功率耗散（最大）:- 电压电源:模拟和数字 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘 供应商设备封装:24-VQFN 裸露焊盘（4x4） 包装:Digi-Reel® 输入数目和类型:8 个单端，单极 产品目录页面:892 (CN2011-ZH PDF) 其它名称:296-25851-6 |
| AD9225ARSZ | 制造商:Analog Devices 功能描述:IC 制造商:Analog Devices 功能描述:IC, ADC, 12BIT, 25MSPS, SSOP-28 |
| AD9225ARSZRL | 功能描述:IC ADC 12BIT 25MSPS 28SSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:12 采样率（每秒）:300k 数据接口:并联 转换器数目:1 功率耗散（最大）:75mW 电压电源:单电源 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-SOIC（0.295"，7.50mm 宽） 供应商设备封装:24-SOIC 包装:带卷 (TR) 输入数目和类型:1 个单端，单极；1 个单端，双极 |
| AD9225ARZ | 功能描述:IC ADC 12BIT 25MSPS 28-SOIC RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1 系列:microPOWER™ 位数:8 采样率（每秒）:1M 数据接口:串行，SPI? 转换器数目:1 功率耗散（最大）:- 电压电源:模拟和数字 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘 供应商设备封装:24-VQFN 裸露焊盘（4x4） 包装:Digi-Reel® 输入数目和类型:8 个单端，单极 产品目录页面:892 (CN2011-ZH PDF) 其它名称:296-25851-6 |
| AD9225ARZRL | 功能描述:IC ADC 12BIT 25MSPS 28SOIC RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:12 采样率（每秒）:300k 数据接口:并联 转换器数目:1 功率耗散（最大）:75mW 电压电源:单电源 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-SOIC（0.295"，7.50mm 宽） 供应商设备封装:24-SOIC 包装:带卷 (TR) 输入数目和类型:1 个单端，单极；1 个单端，双极 |
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