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參數(shù)資料
| 型號： | HCPL-788J |
| 元件分類： | 運動控制電子 |
| 英文描述： | Isolation Amplifier with Short Circuit and Overload Detection(具有短路和過載保護功能的隔離放大器) |
| 中文描述： | 隔離放大器短路和過載檢測（具有短路和過載保護功能的隔離放大器） |
| 文件頁數(shù)： | 17/20頁 |
| 文件大?。?/td> | 277K |
| 代理商： | HCPL-788J |
17
1. The Basics
Historically, motor control current sense designs
have required trade-offs between signal accuracy,
response time, and the use of discrete components
to detect short circuit and overload conditions.
The HCPL-788J greatly simplifies current-sense
designs by providing an output voltage which can
connect directly to an A/D converter as well as
integrated short circuit and overload detection
(eliminating the need for external circuitry). Available
in an auto-insertable, SO-16 package, the HCPL-788J
is smaller than and has better linearity, offset vs.
temperature and Common Mode Rejection (CMR)
performance than most Hall-effect sensors.
The V
REF
input establishes the full scale output
range. V
REF
can be connected to the supply voltage
(V
DD2
) or a voltage between 4 V and V
DD2
. The nom-
inal gain of the HCPL-788J is the output full scale
range divided by 504 mV.
When 3 phases are wire-ORed together, the 3 phase
AC currents are combined to form a DC voltage with
very little ripple on it. This can be simply filtered and
used to monitor the motor load. Moderate overload
currents which don’t trip the FAULT output can thus
be detected easily.
Frequently Asked Questions about the HCPL-788J
1.1:
Why should I use the HCPL-788J for
sensing current when Hall-effect sensors
are available which don’t need an
isolated supply voltage
1.2:
What is the purpose of the V
REF
input
1.3:
What is the purpose of the rectified
(ABSVAL) output on pin 13
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-788J. 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).
This is not necessary, but it will work. If you do, be
sure to use an RC filter on both pin 1 (V
IN+
) and
pin 2 (V
IN-
) to limit the input voltage at both pads.
In PWM motor drives there are brief spikes of cur-
rent flowing in the wires leading to the motor each time
a phase voltage is switched between states. The amp-
litude and duration of these current spikes is deter-
mined by the slew rate of the power transistors and
the wiring impedances. To avoid false tripping of the
FAULT output (pin 14) the HCPL-788J includes a
blanking filter. This filter ignores over-range input
conditions shorter than 1
μ
s. For very long motor
wires, it may be necessary to increase the time con-
stant of the input RC anti-aliasing filter to keep the
peak value of the HCPL-788J inputs below
±
230 mV.
For example, a 39
, 0.047
μ
F RC filter on pin 1 will
ensure that 2
μ
s wide 500 mV pulses across the sense
resistor do not trip the FAULT output.
2.2:
Should I connect both inputs across the
sense resistor instead of grounding V
IN-
directly to pin 8
2.3:
How can I avoid false tripping of the fault
output due to cable capacitance charging
transients
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| HCPL-788J#500 | 功能描述:隔離放大器 4.5 - 5.5 SV 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-788J/EVAL | 制造商:Avago Technologies 功能描述: |
| HCPL-788J-000E | 功能描述:隔離放大器 4.5 - 5.5 SV 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-788J-500E | 功能描述:隔離放大器 4.5 - 5.5 SV 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-800J | 功能描述:緩沖器和線路驅(qū)動器 PLC Powerline DAA IC RoHS:否 制造商:Micrel 輸入線路數(shù)量:1 輸出線路數(shù)量:2 極性:Non-Inverting 電源電壓-最大:+/- 5.5 V 電源電壓-最小:+/- 2.37 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Reel |
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