參數(shù)資料
MCP3021
DS21805A-page 18
2003 Microchip Technology Inc.
6.0
APPLICATIONS INFORMATION
6.1
Driving the Analog Input
The MCP3021 has a single-ended analog input (AIN).
For proper conversion results, the voltage at the AIN
pin must be kept between VSS and VDD. If the converter
has no offset error, gain error, INL or DNL errors and
the voltage level of AIN is equal to or less than
VSS + 1/2 LSB, the resultant code will be 000h. Addi-
tionally, if the voltage at AIN is equal to or greater than
VDD - 1.5 LSB, the output code will be 1FFh.
The analog input model is shown in Figure 6-1. In this
diagram, the source impedance (RSS) adds to the inter-
nal sampling switch (RS) impedance, directly affecting
the time required to charge the capacitor (CSAMPLE).
Consequently, a larger source impedance increases
the offset error, gain error and integral linearity errors of
the conversion. Ideally, the impedance of the signal
source should be near zero. This is achievable with an
operational amplifier such as the MCP6022, which has
a closed-loop output impedance of tens of ohms.
FIGURE 6-1:
Analog Input Model, AIN.
6.2
Connecting to the I2C Bus
The I2C bus is an open collector bus, requiring pull-up
resistors connected to the SDA and SCL lines. This
configuration is shown in Figure 6-2.
FIGURE 6-2:
Pull-up Resistors on I2C
Bus.
The number of devices connected to the bus is limited
only by the maximum bus capacitance of 400 pF. A
possible configuration using multiple devices is shown
FIGURE 6-3:
Multiple Devices on I2C Bus.
CPIN
VA
RSS AIN
7pF
VT = 0.6V
ILEAKAGE
Sampling
Switch
SS
RS = 1 k
CSAMPLE
= DAC capacitance
VSS
VDD
= 20 pF
±1 nA
Legend
VA = signal source
RSS = source impedance
AIN
=
analog input pad
CPIN = analog input pin capacitance
VT = threshold voltage
ILEAKAGE = leakage current at the pin
due to various junctions
SS
=
sampling switch
R
S
=
sampling switch resistor
CSAMPLE = sample/hold capacitance
PI
Cmi
cr
o
SDA
SCL
VDD
RPU
RPU is typically: 10 k for fSCL = 100 kHz
2k
for fSCL = 400 kHz
MCP3021
Analog
Input
Signal
M
icr
ocont
ro
ller
AIN
SDA SCL
PIC16F876
Microcontroller
MCP3021
10-bit ADC
TC74
Temperature
Sensor
24LC01
EEPROM
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MCP3021A4T-E/OT 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10-bit ADC I2C Single Channel RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)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(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
MCP3021A5T-E/OT 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10-bit I2C Sgl Chnl RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)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(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
MCP3021A5T-E/OT-CUT TAPE 制造商:Microchip 功能描述:Single Channel SPI Serial Interface 2.7 V 10-Bit A/D Converter SMT - SOT-23-5
MCP3021A6T-E/OT 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10-bit ADC I2C Single Channel RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)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(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
MCP3021A7T-E/OT 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 10-bit ADC I2C Single Channel RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)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(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
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