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| 型号： | TC7135CBU713 |
| 厂商： | Microchip Technology |
| 文件页数： | 12/28页 |
| 文件大小： | 0K |
| 描述： | IC ADC 4 1/2DGT 64-MQFP |
| 标准包装： | 250 |
| 显示器类型： | LED |
| 配置： | 7 段显示 |
| 接口： | BCD |
| 数字或字符： | A/D，4.5 位数字 |
| 电流 - 电源： | 1mA |
| 电源电压： | 4 V ~ 6 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 64-BQFP |
| 供应商设备封装： | 64-PQFP（14x14） |
| 包装： | 带卷 (TR) |
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TC7135
6.0
TYPICAL APPLICATIONS
6.1.3
AUTO-ZERO AND REFERENCE
CAPACITORS
6.1
6.1.1
Component Value Selection
INTEGRATING RESISTOR
The size of the auto-zero capacitor has some influence
on the noise of the system, with a larger capacitor
reducing the noise. The reference capacitor should be
The integrating resistor R INT is determined by the full-
scale input voltage and the output current of the buffer
used to charge the integrator capacitor (C INT ). Both the
buffer amplifier and the integrator have a class A output
stage, with 100 μA of quiescent current. A 20 μA drive
current gives negligible linearity errors. Values of 5 μA
to 40 μA give good results. The exact value of an
integrating resistor for a 20 μA current is easily
large enough such that stray capacitance to ground
from its nodes is negligible.
The dielectric absorption of the reference and auto-
zero capacitors are only important at power-on or when
the circuit is recovering from an overload. Smaller or
cheaper capacitors can be used if accurate readings
are not required for the first few seconds of recovery.
calculated.
6.1.4
REFERENCE VOLTAGE
R INT = -------------------------------------------
EQUATION 6-1:
20 μ A
6.1.2 INTEGRATING CAPACITOR ( C INT )
The product of integrating resistor and capacitor should
The analog input required to generate a full-scale
output is V IN = 2 V REF .
The stability of the reference voltage is a major factor in
the overall absolute accuracy of the converter. For this
reason, it is recommended that a high-quality reference
be used where high-accuracy absolute measurements
are being made.
be selected to give the maximum voltage swing that
ensures the tolerance build-up will not saturate the
integrator swing (approximately 0.3V from either
supply). For ±5V supplies and ANALOG COMMON tied
6.2
6.2.1
Conversion Timing
LINE FREQUENCY REJECTION
to supply ground, a ±3.5V to ±4V full scale integrator
swing is adequate. A 0.10 μF to 0.47 μF is
recommended. In general, the value of C INT is given
by:
A signal integration period at a multiple of the 60 Hz
line frequency will maximize 60 Hz “line noise”
rejection. A 100 kHz clock frequency will reject 50 Hz,
60 Hz and 400 Hz noise. This corresponds to five
readings per second (see Table 6-1 and Table 6-2 ).
EQUATION 6-2:
[ 10 , 000 × clock period ] × I INT
= ( ----------------------------------------------------------------------------- A -
C INT
= ---------------------------------------------------------------------------
integrator output voltage swing
10 , 000 ) ( clock period ) × 20 μ
integrator output voltage swing
TABLE 6-1: CONVERSION RATE VS.
CLOCK FREQUENCY
Oscillator Frequency Conversion Rate
(kHz) (Conv./Sec.)
100 2.5
A very important characteristic of the integrating
capacitor C INT is that it has low dielectric absorption to
prevent rollover or ratiometric errors. A good test for
dielectric absorption is to use the capacitor with the
input tied to the reference. This ratiometric condition
should read half scale 0.9999, with any deviation
probably due to dielectric absorption. Polypropylene
capacitors give undetectable errors at reasonable cost.
Polystyrene and polycarbonate capacitors may also be
used in less critical applications.
DS21460D-page 12
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? 2007 Microchip Technology Inc.
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| TC7135CKW | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:4-1/2 Digit A/D Converter |
| TC7135CLI | 功能描述:LED显示驱动器 4-1/2 Digit A/D BCD RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
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| TC7135CPI | 功能描述:LED显示驱动器 4-1/2 Digit A/D BCD RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
| TC7135CPL | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:4-1/2 Digit A/D Converter |
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