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| 型号： | ADS1222IPWT |
| 厂商： | Texas Instruments |
| 文件页数： | 26/26页 |
| 文件大小： | 0K |
| 描述： | IC 24BIT ADC W/2CH MUX 14-TSSOP |
| 产品培训模块： | Data Converter Basics |
| 视频文件： | Nuts and Bolts of the Delta-Sigma Converter |
| 标准包装： | 1 |
| 位数： | 24 |
| 采样率（每秒）： | 240 |
| 数据接口： | 串行 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 2.25mW |
| 电压电源： | 模拟和数字 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 14-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 14-TSSOP |
| 包装： | 标准包装 |
| 输入数目和类型： | 4 个单端，单极；2 个差分，双极 |
| 其它名称： | 296-17321-6 |
ADS1222
SBAS314B APRIL 2004 REVISED JANUARY 2009
www.ti.com
9
Analog Input Measurement without the Input Buffer
With the buffer disabled by setting the BUFEN pin low,
the ADS1222 measures the input signal using internal
capacitors
that
are
continuously
charged
and
discharged. Figure 14 shows a simplified schematic of
the ADS1222 input circuitry, with Figure 15 showing the
on/off timings of the switches. The S1 switches close
during the input sampling phase. With S1 closed, CA1
charges to AINP, CA2 charges to AINN, and CB charges
to (AINP – AINN). For the discharge phase, S1 opens
first and then S2 closes. CA1 and CA2 discharge to
approximately VDD/2 and CB discharges to 0V. This
two-phase sample/discharge cycle repeats with a
frequency of fCLK/32 (62.5kHz for fCLK = 2MHz).
Mux
VDD
VDD/2
S
1
S
1
AINN
AINP
S
2
C
A1
3pF
C
B
6pF
C
A2
3pF
VDD
ESD Protection
AINPx
AINNx
S
2
Figure 14. Simplified Input Structure with the
Buffer Turned Off
ON
OFF
ON
S
1
S
2
OFF
t
SAMPLE = 32/fCLK
Figure 15. S1 and S2 Switch Timing for Figure 14
The constant charging of the input capacitors presents
a load on the inputs that can be represented by effective
impedances. Figure 16 shows the input circuitry with
the capacitors and switches of Figure 14 replaced by
their effective impedances. These impedances scale
inversely with fCLK frequency. For example, if fCLK
frequency is reduced by a factor of 2, the impedances
will double.
Zeff
A =tSAMPLE/CA1 =6M
(1)
Zeff
B =tSAMPLE/CB =3M
(1)
Zeff
A =tSAMPLE/CA2 =6M
(1)
NOTE: (1) fCLK =2MHz.
AINPx
AINNx
VDD/2
Figure 16. Effective Analog Input Impedances
with the Buffer Off
ESD diodes protect the inputs. To keep these diodes
from turning on, make sure the voltages on the input
pins do not go below GND by more than 100mV, and
likewise do not exceed VDD by 100mV:
GND – 100mV < (AINP, AINN) < VDD + 100mV
Analog Input Measurement with the Input Buffer
When the buffer is enabled by setting the BUFEN pin
high, a low-drift, chopper-stabilized input buffer is used
to achieve very high input impedance. The buffer
charges the input sampling capacitors, thus removing
the load from the measurement. Because the input
buffer is chopper-stabilized, the charging of parasitic
capacitances causes the charge to be carried away, as
if by resistance. The input impedance can be modeled
by a single resistor, as shown in Figure 17. The
impedance scales inversely with fCLK frequency, as in
the nonbuffered case. Note that during standby mode,
the buffer must be disabled to prevent loading of the
inputs.
AINP
AINN
1.2G
(1)
NOTE: (1) f
CLK =2MHz.
Figure 17. Effective Analog Input Impedances
with the Buffer On
Note also that the analog inputs (listed in the Electrical
Characteristics table as Absolute Input Range) must
remain between GND + 0.05V to VDD 1.5V.
Exceeding this range degrades linearity and results in
performance outside the specified limits.
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相关代理商/技术参数 |
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|---|---|
| ADS1222IPWT | 制造商:Texas Instruments 功能描述:IC 24-BIT ADC 2 CH DIFF I/P MULTI |
| ADS1222IPWTG4 | 功能描述:模数转换器 - ADC 24-Bit Conv w/2-Ch Diff Input Mltplxer RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| ADS1224 | 制造商:BB 制造商全称:BB 功能描述:24-Bit Analog-to-Digital Converter with 4-Channel Differential Input Multiplexer |
| ADS1224EVM | 功能描述:数据转换 IC 开发工具 ADS1224 Eval Mod RoHS:否 制造商:Texas Instruments 产品:Demonstration Kits 类型:ADC 工具用于评估:ADS130E08 接口类型:SPI 工作电源电压:- 6 V to + 6 V |
| ADS1224IPWR | 功能描述:模数转换器 - ADC 24-bit 240SPS RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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