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參數(shù)資料
| 型號： | ADS7816C |
| 英文描述： | 12-Bit High Speed Micro Power Sampling ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 12位高速微功耗采樣模擬到數(shù)字轉換器 |
| 文件頁數(shù)： | 12/13頁 |
| 文件大?。?/td> | 226K |
| 代理商： | ADS7816C |
12
ADS7816
sion, the digital output must be updated with the results of the
last bit decision, the capacitor array appropriately switched
and charged, and the input to the comparator settled to a
12-bit level all within one clock cycle.
The basic SAR architecture is sensitive to spikes on the
power supply, reference, and ground connections that occur
just prior to latching the comparator output. Thus, during
any single conversion for an n-bit SAR converter, there are
n “windows” in which large external transient voltages can
easily affect the conversion result. Such spikes might origi-
nate from switching power supplies, digital logic, and high
power devices, to name a few. This particular source of error
can be very difficult to track down if the glitch is almost
synchronous to the converter’s DCLOCK signal—as the
phase difference between the two changes with time and
temperature, causing sporadic misoperation.
With this in mind, power to the ADS7816 should be clean
and well bypassed. A 0.1
μ
F ceramic bypass capacitor should
be placed as close to the ADS7816 package as possible. In
addition, a 1 to 10
μ
F capacitor and a 10
series resistor may
be used to lowpass filter a noisy supply.
The reference should be similarly bypassed with a 0.1
μ
F
capacitor. Again, a series resistor and large capacitor can be
used to lowpass filter the reference voltage. If the reference
voltage originates from an op amp, be careful that the op-
amp can drive the bypass capacitor without oscillation (the
series resistor can help in this case). Keep in mind that while
the ADS7816 draws very little current from the reference on
average, there are higher instantaneous current demands
placed on the external reference circuitry.
Also, keep in mind that the ADS7816 offers no inherent
rejection of noise or voltage variation in regards to the
reference input. This is of particular concern when the
reference input is tied to the power supply. Any noise and
ripple from the supply will appear directly in the digital
results. While high frequency noise can be filtered out as
ADS7816
μP
DCLOCK
D
OUT
CS/SHDN
A
0
A
1
U
3
U
4
U
1
U
2
Thermocouple
ISO Thermal Block
MUX
OPA237
0.3V
0.4V
0.2V
0.1V
+5V
R
2
59k
R
4
1k
R
3
500k
R
5
500
R
7
10
C
3
0.1μF
C
4
10μF
C
5
0.1μF
R
6
1M
R
1
150k
D
1
TC
2
TC
1
TC
3
+5V
C
2
0.1μF
C
1
10μF
+5V
R
8
46k
R
9
1k
R
10
1k
R
11
1k
R
12
1k
V
REF
3-Wire
Interface
FIGURE 6. Thermocouple Application Using a MUX to Scale the Input Range of the ADS7816.
described in the previous paragraph, voltage variation due to
the line frequency (50Hz or 60Hz), can be difficult to
remove.
The GND pin on the ADS7816 should be placed on a clean
ground point. In many cases, this will be the “analog”
ground. Avoid connecting the GND pin too close to the
grounding point for a microprocessor, microcontroller, or
digital signal processor. If needed, run a ground trace di-
rectly from the converter to the power supply connection
point. The ideal layout will include an analog ground plane
for the converter and associated analog circuitry.
The –In input pin should be connected directly to ground. In
those cases where the ADS7816 is a large distance from the
signal source and/or the circuit environment contains large
EMI or RFI sources, the –In input should be connected to the
ground nearest the signal source. This should be done with
a signal trace that is adjacent to the +In input trace. If
appropriate, coax cable or twisted-pair wire can be used.
APPLICATION CIRCUITS
Figures 6, 7, and 8 show some typical application circuits for
the ADS7816. Figure 6 uses an ADS7816 and a multiplexer
to provide for a flexible data acquisition circuit. A resistor
string provides for various voltages at the multiplexer input.
The selected voltage is buffered and driven into V
REF
. As
shown in Figure 6, the input range of the ADS7816 is
programmable to 100mV, 200mV, 300mV, or 400mV. The
100mV range would be useful for sensors such as the
thermocouple shown.
Figure 7 is more complex variation of Figure 6 with in-
creased flexibility. In this circuit, a digital signal processor
designed for audio applications is put to use in running three
ADS7816s and a DAC56. The DAC56 provides a variable
voltage for V
REF
—enabling the input range of the ADS7816s
to be programmed from 100mV to 3V.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ADS7816E | 制造商:Texas Instruments 功能描述: |
| ADS7816E/250 | 功能描述:模數(shù)轉換器 - ADC 12-Bit High Speed MicroPower Sampling RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率: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 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7816E/250G4 | 功能描述:模數(shù)轉換器 - ADC 12-Bit High Speed MicroPower Sampling RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率: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 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7816E/2K5 | 功能描述:模數(shù)轉換器 - ADC 12-Bit High Speed MicroPower Sampling RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率: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 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7816E/2K5G4 | 功能描述:模數(shù)轉換器 - ADC 12-Bit High Speed MicroPower Sampling RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率: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 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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