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參數(shù)資料
| 型號： | AD8200 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | High Common-Mode Voltage, Single Supply Difference Amplifier |
| 中文描述： | 高共模電壓，單電源差分放大器 |
| 文件頁數(shù)： | 8/8頁 |
| 文件大?。?/td> | 186K |
| 代理商： | AD8200 |
REV. 0
AD8200
–8–
HIGH LINE CURRENT SENSING WITH LPF AND GAIN
ADJUSTMENT
Figure 11 is another refinement of Figure 1, including gain
adjustment and low-pass filtering.
–
IN GND A1
A2
+IN
NC +V
S
OUT
AD8200
5V
OUTPUT
4V/AMP
INDUCTIVE
LOAD
POWER
DEVICE
4 TERM
SHUNT
CLAMP
DIODE
BATTERY
14V
COMMON
C
V
NULL
191k
20k
5% CALIBRATION RANGE
F
= 0.796Hz
–
F
(0.22 F FOR f = 3.6 Hz)
NC = NO CONNECT
Figure 11. High-Line Current Sensor Interface. Gain =
×
40,
Single-Pole, Low-Pass Filter
A power device that is either ‘ON’ or ‘OFF’ controls the current
in the load. The average current is proportional to the duty cycle
of the input pulse, and is sensed by a small value resistor. The
average differential voltage across the shunt is typically 100 mV,
although its peak value will be higher by an amount that depends
on the inductance of the load and the control frequency. The
common-mode voltage, on the other hand, extends from roughly
1 V above ground, when the switch is ‘ON,’ to about 1.5 V
above the battery voltage, when the device is ‘OFF,’ and the
clamp diode conducts. If the maximum battery voltage spikes
up to 20 V, the common-mode voltage at the input can be as
high as 21.5 V.
To produce a full-scale output of 4 V, a gain
×
40 is used, adjust-
able by
±
5% to absorb the tolerance in the shunt. There is
sufficient headroom to allow 10% overrange (to 4.4 V). The
roughly triangular voltage across the sense resistor is averaged
by a single-pole, low-pass filter, here set with a corner frequency
= 3.6 Hz, which provides about 30 dB of attenuation at 100 Hz.
A higher rate of attenuation can be obtained using a two-pole
filter having f
C
= 20 Hz, as shown in Figure 12. Although this
circuit uses two separate capacitors, the total capacitance is less
than half that needed for the single-pole filter.
–
IN GND A1
A2
+IN
NC +V
S
OUT
AD8200
5V
OUTPUT
INDUCTIVE
LOAD
POWER
DEVICE
4 TERM
SHUNT
CLAMP
DIODE
BATTERY
14V
COMMON
C
127k
432k
50k
F
= 1Hz
–
F
(0.05 F FOR f
C
= 20Hz)
C
NC = NO CONNECT
Figure 12. Illustration of 2-Pole Low-Pass Filtering
DRIVING CHARGE REDISTRIBUTION A/D
CONVERTERS
When driving CMOS ADCs, such as those embedded in popular
microcontrollers, the charge injection ( Q) can cause a signifi-
cant deflection in the output voltage of the AD8200. Though
generally of short duration, this deflection may persist until after
the sample period of the ADC has expired, due to the relatively
high open-loop output impedance of the AD8200. Including an
R-C network in the output can significantly reduce the effect.
The capacitor helps to absorb the transient charge, effectively
lowering the high-frequency output impedance of the AD8200.
For these applications, the output signal should be taken from the
midpoint of the R
LAG
–C
LAG
combination as shown in Figure 13.
Since the perturbations from the analog-to-digital converter are
small, the output impedance of the AD8200 will appear to be
low. The transient response will, therefore, have a time constant
governed by the product of the two LAG components, C
LAG
×
R
LAG
. For the values shown in Figure 13, this time constant is
programmed at approximately 10
μ
s. Therefore, if samples are
taken at several tens of microseconds or more, there will be
negligible charge “stack-up.”
+IN
–
IN
10k
10k
AD8200
5V
R
LAG
1k
C
0.01 F
PROCESSOR
A/D
A2
Figure 13. Recommended Circuit for Driving CMOS A/D
C
P
8-Lead SOIC Package
(SO-8)
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8
0
0.0196 (0.50)
0.0099 (0.25)
45
8
5
4
1
0.1968 (5.00)
0.1890 (4.80)
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.1574 (4.00)
0.1497 (3.80)
0.0500 (1.27)
BSC
0.0688 (1.75)
0.0532 (1.35)
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8200_03 | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Common-Mode Voltage, Single-Supply Difference Amplifier |
| AD8200CHIPS | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Common-Mode Voltage, Single Supply Difference Amplifier |
| AD8200R | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Common-Mode Voltage, Single Supply Difference Amplifier |
| AD8200YCHIPS | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Common-Mode Voltage, Single-Supply Difference Amplifier |
| AD8200YCSURF | 制造商:Analog Devices 功能描述: |
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