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參數(shù)資料
| 型號(hào)： | HCPL-7840 |
| 元件分類： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | Isolation Amplifier(隔離放大器) |
| 中文描述： | 隔離放大器（隔離放大器） |
| 文件頁(yè)數(shù)： | 16/19頁(yè) |
| 文件大?。?/td> | 244K |
| 代理商： | HCPL-7840 |
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FREQUENTLY ASKED QUESTIONS ABOUT THE HCPL-7840
1. THE BASICS
1.1: Why should I use the HCPL-7840 for sensing current when Hall-effect sensors are available
which don’t need an isolated supply voltage
Available in an auto-insertable, 8-pin DIP package, the HCPL-7840 is smaller than and has better linearity,
offset vs. temperature and Common Mode Rejection (CMR) performance than most Hall-effect sensors.
Additionally, often the required input-side power supply can be derived from the same supply that powers
the gate-drive optocoupler.
2. SENSE RESISTOR AND INPUT FILTER
2.1: Where do I get 10 m
resistors I have never seen one that low.
Although less common than values above 10
, there are quite a few manufacturers of resistors suitable for
measuring currents up to 50 A when combined with the HCPL- 7840.
Example product information may be found at Dale’s web site (http://www.vishay.com/vishay/dale) and
Isotek’s web site (http://www.isotekcorp.com).
2.2: Should I connect both inputs across the sense resistor instead of grounding V
IN-
directly
to pin 4
This is not necessary, but it will work. If you do, be sure to use an RC filter on both pin 2 (V
IN+
) and pin 3
(V
IN-
) to limit the input voltage at both pads.
2.3: Do I really need an RC filter on the input What is it for Are other values of R and C okay
The input anti-aliasing filter (R=39
, C=0.01
μ
F) shown in the typical application circuit is recommended
for filtering fast switching voltage transients from the input signal. (This helps to attenuate higher signal
frequencies which could otherwise alias with the input sampling rate and cause higher input offset voltage.)
Some issues to keep in mind using different filter resistors or capacitors are:
1. (Filter resistor:) Input bias current for pins 2 and 3: This is on the order of 500 nA. If you are using a
single filter resistor in series with pin 2 but not pin 3 the IxR drop across this resistor will add to the offset
error of the device. As long as this IR drop is small compared to the input offset voltage there should not be
a problem. If larger-valued resistors are used in series, it is better to put half of the resistance in series with
pin 2 and half the resistance in series with pin 3. In this case, the offset voltage is due mainly to resistor
mismatch (typically less than 1% of the resistance design value) multiplied by the input bias.
2. (Filter resistor:) The equivalent input resistance for -7840 is around 500 k
. It is therefore best to
ensure that the filter resistance is not a significant percentage of this value; otherwise the offset voltage will
be increased through the resistor divider effect. [As an example, if R
filt
= 5.5 k
, then V
OS
= (Vin * 1%) =
2 mV for a maximum 200 mV input and V
OS
will vary with respect with Vin.]
3. The input bandwidth is changed as a result of this different R-C filter configuration. In fact this is one of
the main reasons for changing the input-filter R-C time constant.
4. (Filter capacitance:) The input capacitance of the -78XX is approximately 1.5 pF. For proper operation
the switching input-side sampling capacitors must be charged from a relatively fixed (low impedance)
voltage source. Therefore, if a filter capacitor is used it is best for this capacitor to be a few orders of
magnitude greater than the C
INPUT
(A value of at least 100 pF works well.)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| HCPL-7850 | Hermetically Sealed Analog Isolation Amplifier(密封模擬隔離放大器) |
| HCPL-7851 | Hermetically Sealed Analog Isolation Amplifier(密封模擬隔離放大器) |
| HCPL-7870 | Isolated 15-bit A/D Converter(隔離15位A/D轉(zhuǎn)換器) |
| HCPL-788J | Isolation Amplifier with Short Circuit and Overload Detection(具有短路和過(guò)載保護(hù)功能的隔離放大器) |
| HCPL-810J | PLC Powerline DAA IC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| HCPL-7840#060 | 功能描述:隔離放大器 4.5 - 5.5 SV 8 dB RoHS:否 制造商:Texas Instruments 輸入補(bǔ)償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
| HCPL-7840#300 | 功能描述:隔離放大器 4.5 - 5.5 SV 8 dB RoHS:否 制造商:Texas Instruments 輸入補(bǔ)償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
| HCPL-7840#360 | 功能描述:隔離放大器 4.5 - 5.5 SV 8 dB RoHS:否 制造商:Texas Instruments 輸入補(bǔ)償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
| HCPL-7840#500 | 功能描述:隔離放大器 4.5 - 5.5 SV 8 dB RoHS:否 制造商:Texas Instruments 輸入補(bǔ)償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
| HCPL-7840#560 | 功能描述:隔離放大器 4.5 - 5.5 SV 8 dB RoHS:否 制造商:Texas Instruments 輸入補(bǔ)償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
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