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参数资料
| 型号： | LMP90079MH/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PDSO28 |
| 封装： | LEAD FREE, PLASTIC, MO-153, TSSOP-28 |
| 文件页数： | 33/62页 |
| 文件大小： | 1721K |
| 代理商： | LMP90079MH/NOPB |
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17.0 Applications Information
17.1 QUICK START
This section shows step-by-step instructions to configure the
LMP900xx to perform a simple DC reading from CH0.
1.
Apply VA = VIO = VREFP1 = 5V, and ground VREFN1
2.
Apply VINP = VREF and VINN = VREF for CH0.
Thus, set CH0 = VIN = VINP - VINN = VREF
(CH0_INPUTCN register)
3.
Set gain = 1 (CH0_CONFIG: GAIN_SEL = 0x0)
4.
Exclude the buffer from the signal path (CH0_CONFIG:
BUF_EN = 1)
5.
Set the background to BgcalMode2 (BGCALCN = 0x2)
6.
Select VREF1 (CH0_INPUTCN: VREF_SEL = 0)
7.
To use the internal CLK, set CLK_EXT_DET = 1 and
CLK_SEL = 0.
8.
Follow the register read/write protocol (Figure 19) to
capture ADC_DOUT from CH0.
17.2 CONNECTING THE SUPPLIES
17.2.1 VA and VIO
Any ADC architecture is sensitive to spikes on the analog
voltage, VA, digital input/output voltage, VIO, and ground
pins. These spikes may originate from switching power sup-
plies, digital logic, high power devices, and other sources. To
diminish these spikes, the LMP900xx’s VA and VIO pins
should be clean and well bypassed. A 0.1 F ceramic bypass
capacitor and a 1 F tantalum capacitor should be used to
bypass the LMP900xx supplies, with the 0.1 F capacitor
placed as close to the LMP900xx as possible.
Since the LMP900xx has both external VA and VIO pins, the
user has two options on how to connect these pins. The first
option is to tie VA and VIO together and power them with the
same power supply. This is the most cost effective way of
powering the LMP900xx but is also the least ideal because
noise from VIO can couple into VA and negatively affect per-
formance. The second option involves powering VA and VIO
with separate power supplies. These supply voltages can
have the same amplitude or they can be different.
17.2.2 VREF
Operation with VREF below VA is also possible with slightly
diminished performance. As VREF is reduced, the range of
acceptable analog input voltages is also reduced. Reducing
the value of VREF also reduces the size of the LSB. When
the LSB size goes below the noise floor of the LMP900xx, the
noise will span an increasing number of codes and perfor-
mance will degrade. For optimal performance, VREF should
be the same as VA and sourced with a clean source that is
bypassed with a ceramic capacitor value of 0.1 F and a tan-
talum capacitor of 10 F.
LMP900xx also allows ratiometric connection for noise im-
munity reasons. A ratiometric connection is when the ADC’s
VREFP and VREFN are used to excite the input device’s (i.e.
a bridge sensor) voltage references. This type of connection
severely attenuates any VREF ripple seen the ADC output,
and is thus strongly recommended.
17.3 ADC_DOUT CALCULATION
The output code of the LMP900xx can be calculated as:
Equation 1 — Output Code
ADC_DOUT is in 16bit two's complement binary format. The
largest positive value is 0x7FFF (or 32767 in decimal), while
the largest negative value is 0x8000 (or 32768 in decimal). In
case of an over range the value is automatically clamped to
one of these two values.
Figure 30 shows the theoretical output code, ADC_DOUT, vs.
analog input voltage, VIN, using the equation above.
30169747
FIGURE 30. ADC_DOUT vs. VIN of a 16-Bit Resolution
(VREF = 5.5V, Gain = 1).
39
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LMP90080/LMP90079/LMP90078/LMP90077
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LMP90079MHX/NOPB | 功能描述:模数转换器 - 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 |
| LMP90080 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Sensor AFE System: Multi-Channel, Low-Power 16-Bit |
| LMP90080MH/NOPB | 功能描述:模数转换器 - 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 |
| LMP90080MHE/NOPB | 功能描述:模数转换器 - 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 |
| LMP90080MHX/NOPB | 功能描述:模数转换器 - 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 |
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