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參數資料
| 型號： | HCPL-7840 |
| 元件分類： | 運動控制電子 |
| 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） |
| 文件頁數： | 15/19頁 |
| 文件大?。?/td> | 244K |
| 代理商： | HCPL-7840 |
15
the load current should have no
impact on the measured voltage.
When laying out a PC board for
the current sensing resistors, a
couple of points should be kept
in mind. The Kelvin connections
to the resistor should be brought
together under the body of the
resistor and then run very close
to each other to the input of the
HCPL-7840; this minimizes the
loop area of the connection and
reduces the possibility of stray
magnetic fields from interfering
with the measured signal. If
the sense resistor is not located
on the same PC board as the
HCPL-7840 circuit, a tightly
twisted pair of wires can
accomplish the same thing.
Also, multiple layers of the PC
board can be used to increase
current carrying capacity.
Numerous plated-through vias
should surround each non-Kelvin
terminal of the sense resistor
to help distribute the current
between the layers of the PC
board. The PC board should use
2 or 4 oz. copper for the layers,
resulting in a current carrying
capacity in excess of 20 A.
Making the current carrying
traces on the PC board fairly
large can also improve the sense
resistor’s power dissipation
capability by acting as a heat
sink. Liberal use of vias where
the load current enters and exits
the PC board is also
recommended.
Sense Resistor Connections
The recommended method for
connecting the HCPL-7840 to the
current sensing resistor is shown
in Figure 18. V
IN+
(pin 2 of the
HPCL-7840) is connected to the
positive terminal of the sense
resistor resistor, while V
IN-
(pin
3) is shorted to GND1 (pin 4),
with the power-supply return
path functioning as the sense line
to the negative terminal of the
current sense resistor. This
allows a single pair of wires or
PC board traces to connect the
HCPL-7840 circuit to the sense
resistor. By referencing the input
circuit to the negative side of the
sense resistor, any load current
induced noise transients on the
resistor are seen as a common-
mode signal and will not interfere
with the current-sense signal.
This is important because the
large load currents flowing
through the motor drive, along
with the parasitic inductances
inherent in the wiring of the
circuit, can generate both noise
spikes and offsets that are
relatively large compared to the
small voltages that are being
measured across the current
sensing resistor.
If the same power supply is used
both for the gate drive circuit
and for the current sensing
circuit, it is very important that
the connection from GND1 of the
HCPL-7840 to the sense resistor
be the only return path for supply
current to the gate drive power
supply in order to eliminate
potential ground loop problems.
The only direct connection
between the HCPL-7840 circuit
and the gate drive circuit should
be the positive power supply line.
Output Side
The op-amp used in the external
post-amplifier circuit should be of
sufficiently high precision
so that it does not contribute
a significant amount of offset
or offset drift relative to the
contribution from the isolation
amplifier. Generally, op-amps
with bipolar input stages exhibit
better offset performance than
op-amps with JFET or MOSFET
input stages.
In addition, the op-amp should
also have enough bandwidth
and slew rate so that it does not
adversely affect the response
speed of the overall circuit. The
post-amplifier circuit includes a
pair of capacitors (C5 and C6)
that form a single-pole low-pass
filter; these capacitors allow the
bandwidth of the post-amp to
be adjusted independently of the
gain and are useful for reducing
the output noise from the isola-
tion amplifier. Many different op-
amps could be used in the circuit,
including: MC34082A (Motorola),
TLO32A, TLO52A, and TLC277
(Texas Instruments), LF412A
(National Semiconductor).
The gain-setting resistors in the
post-amp should have a tolerance
of 1% or better to ensure adequate
CMRR and adequate gain toler-
ance for the overall circuit.
Resistor networks can be used
that have much better ratio
tolerances than can be achieved
using discrete resistors. A
resistor network also reduces
the total number of components
for the circuit as well as the
required board space.
Please refer to Agilent
Applications Note 1078 for
additional information on using
Isolation Amplifiers.
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| HCPL-7850 | Hermetically Sealed Analog Isolation Amplifier(密封模擬隔離放大器) |
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| HCPL-7870 | Isolated 15-bit A/D Converter(隔離15位A/D轉換器) |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| 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 安裝風格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
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