LTC2494
2494fd
Figure 19. Input Normal Mode Rejection, Internal
Oscillator and 50Hz Rejection Mode
Figure 20. Input Normal Mode Rejection, Internal
Oscillator and 60Hz Rejection Mode
applications inForMation
In addition to the reference sampling charge, the reference
ESDprojectiondiodeshaveatemperaturedependentleak-
age current. This leakage current, nominally 1nA (±10nA
max) results in a small gain error. A 100
Ω reference
resistance will create a 0.5V full-scale error.
Normal Mode Rejection and Anti-Aliasing
One of the advantages delta-sigma ADCs offer over
conventional ADCs is on-chip digital filtering. Combined
with a large oversample ratio, the LTC2494 significantly
simplifies anti-aliasing filter requirements. Additionally,
the input current cancellation feature allows external low
pass filtering without degrading the DC performance of
the device.
The SINC4 digital filter provides excellent normal mode
rejection at all frequencies except DC and integer multiples
of the modulator sampling frequency (fS) (see Figures
19 and 20). The modulator sampling frequency is fS =
15,360Hz while operating with its internal oscillator and
fS = FEOSC/20 when operating with an external oscillator
of frequency FEOSC.
Whenusingtheinternaloscillator,theLTC2494isdesigned
to reject line frequencies. As shown in Figure 21, rejec-
tion nulls occur at multiples of frequency fN, where fN is
determined by the input control bits FA and FB (fN = 50Hz
or 60Hz or 55Hz for simultaneous rejection). Multiples of
themodulatorsamplingrate(fS=fN256)onlyrejectnoise
to 15dB (see Figure 22), if noise sources are present at
these frequencies anti-aliasing will reduce their effects.
Figure 21. Input Normal Mode Rejection at DC
Figure 22. Input Normal Mode Rejection at fS = 256 fN
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
0 fS 2fS 3fS 4fS 5fS 6fS 7fS 8fS 9fS10fS11fS12fS
INPUT
NORMAL
MODE
REJECTION
(dB)
2494 F19
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
0
fS
INPUT
NORMAL
MODE
REJECTION
(dB)
2494 F20
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
2fS 3fS 4fS 5fS 6fS 7fS 8fS 9fS 10fS
INPUT SIGNAL FREQUENCY (Hz)
INPUT
NORMAL
MODE
REJECTION
(dB)
2494 F21
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
fN
0
2fN 3fN 4fN 5fN 6fN 7fN 8fN
fN = fEOSC/5120
INPUT SIGNAL FREQUENCY (Hz)
250fN 252fN 254fN 256fN 258fN 260fN 262fN
INPUT
NORMAL
MODE
REJECTION
(dB)
2494 F22
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
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LTC2495CUHF 制造商:Linear Technology 功能描述:ADC Single Delta-Sigma 15sps 16-bit Serial 38-Pin QFN EP
LTC2495CUHF#PBF 功能描述:IC ADC 16BIT W/PGA 38-QFN 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:16 采样率(每秒):45k 数据接口:串行 转换器数目:2 功率耗散(最大):315mW 电压电源:模拟和数字 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:28-SOIC(0.295",7.50mm 宽) 供应商设备封装:28-SOIC W 包装:带卷 (TR) 输入数目和类型:2 个单端,单极
LTC2495CUHF#TRPBF 功能描述:IC ADC 16BIT W/PGA 38-QFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:2,500 系列:- 位数:16 采样率(每秒):15 数据接口:MICROWIRE?,串行,SPI? 转换器数目:1 功率耗散(最大):480µW 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:38-WFQFN 裸露焊盘 供应商设备封装:38-QFN(5x7) 包装:带卷 (TR) 输入数目和类型:16 个单端,双极;8 个差分,双极 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494
LTC2495IUHF#PBF 功能描述:IC ADC 16BIT W/PGA 38-QFN 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
LTC2495IUHF#TRPBF 功能描述:IC ADC 16BIT W/PGA 38-QFN 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:16 采样率(每秒):45k 数据接口:串行 转换器数目:2 功率耗散(最大):315mW 电压电源:模拟和数字 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:28-SOIC(0.295",7.50mm 宽) 供应商设备封装:28-SOIC W 包装:带卷 (TR) 输入数目和类型:2 个单端,单极
LTC2496CUHF#PBF 功能描述:IC ADC 16BIT DELTA SIG 38-QFN 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
LTC2496CUHF#TRPBF 功能描述:IC ADC 16BIT DELTA SIG 38-QFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:2,500 系列:- 位数:16 采样率(每秒):15 数据接口:MICROWIRE?,串行,SPI? 转换器数目:1 功率耗散(最大):480µW 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:38-WFQFN 裸露焊盘 供应商设备封装:38-QFN(5x7) 包装:带卷 (TR) 输入数目和类型:16 个单端,双极;8 个差分,双极 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494
LTC2496IUHF#PBF 功能描述:IC ADC 16BIT DELTA SIG 38-QFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:2,500 系列:- 位数:16 采样率(每秒):15 数据接口:MICROWIRE?,串行,SPI? 转换器数目:1 功率耗散(最大):480µW 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:38-WFQFN 裸露焊盘 供应商设备封装:38-QFN(5x7) 包装:带卷 (TR) 输入数目和类型:16 个单端,双极;8 个差分,双极 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494