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参数资料
| 型号： | AD8212 |
| 厂商： | Analog Devices, Inc. |
| 英文描述： | High Voltage Current Shunt Monitor |
| 中文描述： | 高压电流分流监控 |
| 文件页数： | 10/16页 |
| 文件大小： | 310K |
| 代理商： | AD8212 |
AD8212
HIGH VOLTAGE OPERATION USING AN EXTERNAL
PNP TRANSISTOR
The AD8212 offers features that simplify measuring current in
the presence of common-mode voltages greater than 65 V. This
is achieved by connecting an external PNP transistor at the
output of the AD8212 as shown in Figure 23. The V
CE
break-
down voltage of this PNP becomes the operating common-mode
range of the AD8212. PNP transistors with breakdown voltages
exceeding 300 V, are readily available, inexpensive, and available
in small packages.
Rev. 0 | Page 10 of 16
R
OUT
Q2
AD8212
BATTERY
R
SHUNT
0
1
8
5
2
3
OUTPUT
CURRENT
COMPENSATION
BIAS
CIRCUIT
L
R1
R2
A1
Q1
VOUT
R
BIAS
6
Figure 23. High Voltage Operation Using External PNP
The AD8212 features an integrated 5 V series regulator. This
regulator ensures that at all times COM (Pin 2), which is the
most negative of all the terminals, is always 5 V less than the
supply voltage (V+). Assuming a battery voltage (V+) of 100 V,
it follows that the voltage at COM (Pin 2) is
(
V
+)
– 5 V = 95 V
The base emitter junction of Transistor Q2, in addition to the
V
be
of one internal transistor, makes the collector of Transistor Q1
approximately equal to
95 V + 2(
V
be(Q2)
)
= 95 V + 1.2 V = 96.2 V
This voltage appears across external Transistor Q2. The voltage
across Transistor Q1 is
100 V – 96.2 V = 3.8 V
In this manner, Transistor Q2 withstands 95.6 V and the
internal Transistor Q1 is only subjected to voltages well below
its breakdown capability.
In this mode of operation, the supply current (I
BIAS
) of the
AD8212 circuit increases based on the supply range and the
R
BIAS
resistor chosen. For example:
if
V+ = 500 V and
R
BIAS
= 500 kΩ
I
BIAS
= (V+ 5 V)/
R
BIAS
then,
I
BIAS
= (500 – 5)/500 kΩ = 990 μA
In high voltage operation, it is recommended that I
BIAS
remain
within 200 μA to 1 mA. This ensures that the bias circuit is
turned on, allowing the device to function as expected. At the
same time, the current through the bias circuit/regulator is
limited to 1 mA. Refer to Figure 19 and Figure 21 for I
BIAS
and
V+ information when using the AD8212 in a high voltage
configuration.
When operating the AD8212, as depicted in Figure 23,
Transistor Q2 can be a FET or a bipolar PNP transistor. The
latter is much less expensive, however the magnitude of I
OUT
conducted to the output resistor (R
OUT
) is reduced by the
amount of current lost through the base of the PNP. This leads
to an error in the output voltage reading.
The AD8212 includes an integrated patented circuit, which
compensates for the output current that is lost through the base
of the external PNP transistor. This ensures that the correct
transconductance of the amplifier is maintained. The user can
opt for an inexpensive bipolar PNP, instead of a FET, while
maintaining a comparable level of accuracy.
OUTPUT CURRENT COMPENSATION CIRCUIT
The base of the external PNP, Q2, is connected to ALPHA
(Pin 6) of the AD8212. The current flowing in this path is
mirrored inside the current compensation circuit. This
current then flows in Resistor R2, which is the same value
as Resistor R1. The voltage created by this current across
Resistor R2, displaces the noninverting input of Amplifier A1
by the corresponding voltage. Amplifier A1 responds by driving
the base of Transistor Q1 so as to force a similar voltage
displacement across Resistor R1, thereby increasing I
OUT
.
Since the current generated by the output compensation circuit
is equal to the base current of Transistor Q2, and the resulting
displacements across Resistor R1 and Resistor R2 result in equal
currents, the increment of current added to the output current
is equivalent to the base current of Transistor Q2. Therefore, the
integrated output current compensation circuit has corrected
I
OUT
such that no error results from the base current lost at
Transistor Q2.
This feature of the AD8212 greatly improves I
OUT
accuracy and
allows the user to choose an inexpensive bipolar PNP (with low
beta) with which to monitor current in the presence of high
voltages (typically several hundred volts).
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8212_07 | 制造商:AD 制造商全称:Analog Devices 功能描述:High Voltage Current Shunt Monitor |
| AD8212AL/QMLR | 制造商:Analog Devices 功能描述: |
| AD8212AL-EMX | 制造商:Analog Devices 功能描述:ENGINEERING VERSION OF AD8212AL/QMLR - Rail/Tube |
| AD8212WYRMZ | 功能描述:IC CURRENT MONITOR 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳流/电流管理 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 功能:电流开关 检测方法:- 精确度:±10% 输入电压:1.7 V ~ 5.5 V 电流 - 输出:600mA 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-UFQFN 供应商设备封装:10-UTQFN（1.4x1.8） 包装:管件 |
| AD8212WYRMZ1 | 制造商:AD 制造商全称:Analog Devices 功能描述:High Voltage Current Shunt Monitor |
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