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參數(shù)資料
| 型號： | 7135CN |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | 4 1/2-DIGIT PRECISION ANALOG-TO-DIGITAL CONVERTERS |
| 中文描述： | 4 ?位精度的模擬數(shù)字轉換器 |
| 文件頁數(shù)： | 9/11頁 |
| 文件大?。?/td> | 146K |
| 代理商： | 7135CN |
ICL7135C, TLC7135C
4 1/2-DIGIT PRECISION
ANALOG-TO-DIGITAL CONVERTERS
SLAS074B – DECEMBER 1986 – REVISED MAY 1999
9
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
integrating capacitor
The product of the integrating resistor and capacitor should be selected to give the maximum voltage swing
without causing the integrating amplifier output to saturate and get too close to the power supply voltages. When
the amplifier output is within 0.3 V of either supply, saturation occurs. With
±
5-V supplies and ANLG COMMON
connected to ground, the designer should design for a
±
3.5-V to
±
4-V integrating amplifier swing. A nominal
capacitor value is 0.47
μ
F. The equation for determining the value of the integrating capacitor (C
INT
) is:
CINT
10,000
Integrator Output Voltage Swing
Clock Period
IINT
Where:
I
INT
is nominally 20
μ
A.
Capacitors with large tolerances and high dielectric absorption can induce conversion inaccuracies. A capacitor
that is too small could cause the integrating amplifier to saturate. High dielectric absorption causes the effective
capacitor value to be different during the signal integrate and deintegrate phases. Polypropylene capacitors
have very low dielectric absorption. Polystyrene and polycarbonate capacitors have higher dielectric
absorption, but also work well.
auto-zero and reference capacitor
Large capacitors tend to reduce noise in the system. Dielectric absorption is unimportant except during power
up or overload recovery. Typical values are 1
μ
F.
reference voltage
For high-accuracy absolute measurements, a high quality reference should be used.
rollover resistor and diode
The ICL7135C and TLC7135C have a small rollover error; however, it can be corrected. The correction is to
connect the cathode of any silicon diode to INT OUT and the anode to a resistor. The other end of the resistor
is connected to ANLG COMMON or ground. For the recommended operating conditions, the resistor value is
100 k
. This value may be changed to correct any rollover error that has not been corrected. In many noncritical
applications the resistor and diode are not needed.
maximum clock frequency
For most dual-slope A/D converters, the maximum conversion rate is limited by the frequency response of the
comparator. In this circuit, the comparator follows the integrator ramp with a 3-
μ
s delay. Therefore, with a
160-kHz clock frequency (6-
μ
s period), half of the first reference integrate clock period is lost in delay. Hence,
the meter reading changes from 0 to 1 with a 50-
μ
V input, 1 to 2 with a 150-
μ
V input, 2 to 3 with a 250-
μ
V input,
etc. This transition at midpoint is desirable; however, when the clock frequency is increased appreciably above
160 kHz, the instrument flashes 1 on noise peaks even when the input is shorted. The above transition points
assume a 2-V input range is equivalent to 20,000 clock cycles.
When the input signal is always of one polarity, comparator delay need not be a limitation. Clock rates of 1 MHz
are possible since nonlinearity and noise do not increase substantially with frequency. For a fixed clock
frequency, the extra count or counts caused by comparator delay are a constant and can be subtracted out
digitally.
For signals with both polarities, the clock frequency can be extended above 160 kHz without error by using a
low value resistor in series with the integrating capacitor. This resistor causes the integrator to jump slightly
towards the zero-crossing level at the beginning of the deintegrate phase, and thus compensates for the
comparator delay. This series resistor should be 10
to 50
. This approach allows clock frequencies up to
480 kHz.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| 7135N | 功能描述:烙鐵 Weller Tip/Hex Nut For 8200 Solder Gun RoHS:否 制造商:Weller 產(chǎn)品:Soldering Stations 類型:Digital, Iron, Stand, Cleaner 瓦特:50 W 最大溫度:+ 850 F 電纜類型:US Cord Included |
| 7135-P | 功能描述:SHEARS ADJUSTABLE TENSION 制造商:klein tools, inc. 系列:Heritage 零件狀態(tài):在售 特性:可調(diào)張力，軟握把 重量:0.09 磅（40.82g） 標準包裝:6 |
| 7135W | 功能描述:烙鐵 Weller Tip For 8200 Solder Gun RoHS:否 制造商:Weller 產(chǎn)品:Soldering Stations 類型:Digital, Iron, Stand, Cleaner 瓦特:50 W 最大溫度:+ 850 F 電纜類型:US Cord Included |
| 7136 | 制造商:VISUAL COMMUNICATIONS COMPANY LLC 功能描述:7136 /Custom Part |
| 7136 WAF | 制造商:Rochester Electronics LLC 功能描述: |
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