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| 型号： | ADS7812UB/1KE4 |
| 厂商： | Texas Instruments |
| 文件页数： | 6/24页 |
| 文件大小： | 0K |
| 描述： | IC 12BIT 35MW SER OUT ADC 16SOIC |
| 产品培训模块： | Data Converter Basics |
| 标准包装： | 1,000 |
| 位数： | 12 |
| 采样率（每秒）： | 40k |
| 数据接口： | 串行，SPI? |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 35mW |
| 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： | 16-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 16-SOIC |
| 包装： | 带卷 (TR) |
| 输入数目和类型： | 3 个单端，单极；3 个单端，双极 |
ADS7812
14
SBAS042A
www.ti.com
The range for the external reference is 2.3V to 2.7V. The
voltage on REF determines the full-scale range of the con-
verter and the corresponding LSB size. Increasing the refer-
ence voltage will increase the LSB size in relation to the
internal noise sources which, in turn, can improve signal-to-
noise ratio. Likewise, decreasing the reference voltage will
reduce the LSB size and signal-to-noise ratio.
CAP
The CAP pin is used to compensate the internal reference
buffer. A 1
F tantalum capacitor in parallel with a 0.01F
ceramic capacitor should be connected between this pin and
ground, with the ceramic capacitor placed as close as pos-
sible to the ADS7812. The total value of the capacitance on
the CAP pin is critical to optimum performance of the
ADS7812. A value larger than 2.0
F could overcompensate
the buffer while a value lower than 0.5
F may not provide
adequate compensation.
BUF
The voltage on the BUF pin is the output of the internal
reference buffer. This pin is used to provide +2.5V to the
analog input or inputs for the various input configurations.
The BUF output can provide up to 1mA of current to an
external load. The load should be constant as a variable load
could affect the conversion result by modulating the BUF
voltage. Also note that the BUF output will show significant
glitches as each bit decision is made during a conversion.
Between conversions, the BUF output is quiet.
POWER DOWN
The ADS7812 has a power-down mode that is activated by
taking CONV LOW and then PWRD HIGH. This will
power down all of the analog circuitry including the refer-
ence, reducing power dissipation to under 50
W. To exit the
power-down mode, CONV is taken HIGH and then PWRD
is taken LOW. Note that a conversion will be initiated if
PWRD is taken HIGH while CONV is LOW.
While in the power-down mode, the voltage on the capaci-
tors connected to CAP and REF will begin to leak off. The
voltage on the CAP capacitor leaks off much more rapidly
than the REF capacitor (the REF input of the ADS7812
becomes high impedance when PWDN is HIGH—this is not
true for the CAP input). When the power-down mode is
exited, these capacitors must be allowed to recharge and
settle to a 12-bit level. Figure 11 shows the amount of time
typically required to obtain a valid 12-bit result based on the
amount of time spent in power down (at room temperature).
This figure assumes that the total capacitance on the CAP
pin is 1.01
F.
Figure 12 provides a circuit which can significantly reduce
the power up time if the power down time will be fairly brief
(a few seconds or less). A low on-resistance MOSFET is
used to disconnect the capacitance on the CAP pin from the
leakage paths internal to the ADS7812. This allows the
capacitors to retain their charge for a much longer period of
time, reducing the time required to recharge them at power
up. With this circuit, the power down time can be extended
to tens or hundreds of milliseconds with almost instanta-
neous power up.
FIGURE 12. Improved Power-Up Response Circuit.
FIGURE 11. Power-Down to Power-Up Response.
POWER-DOWN TO POWER-UP RESPONSE
Power-Down Duration (ms)
Power-Up
Time
to
Rated
Accuracy
(s)
300
250
200
150
100
50
0
0.1
1
10
100
T
A = +25°C
V
S
PWRD
BUSY
CS
CONV
EXT/INT
DATA
DATACLK
R1
IN
GND
R2
IN
R3
IN
BUF
CAP
REF
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
1
2
3
4
8
7
6
5
0.01F
1F
1RF7604
+
Power-Down Signal
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相关代理商/技术参数 |
参数描述 |
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| ADS7812UBE4 | 功能描述:模数转换器 - ADC Low-Power Serial 12-Bit Sampling 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 |
| ADS7812UBG4 | 功能描述:模数转换器 - ADC Low-Pwr Serial 12B Sampling ADC 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 |
| ADS7812UE4 | 功能描述:模数转换器 - ADC Low-Power Serial 12-Bit Sampling 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 |
| ADS7812UG4 | 功能描述:模数转换器 - ADC Low-Pwr Serial 12B Sampling ADC 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 |
| ADS7813 | 制造商:BB 制造商全称:BB 功能描述:Low-Power, Serial 16-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
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