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參數(shù)資料
| 型號(hào)： | AD8555 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Zero-Drift, Digitally Programmable Sensor Signal Amplifier |
| 中文描述： | 零漂移，數(shù)字可編程傳感器信號(hào)放大器 |
| 文件頁數(shù)： | 17/28頁 |
| 文件大小： | 503K |
| 代理商： | AD8555 |
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AD8555
THEORY OF OPERATION
A1, A2, R1, R2, R3, P1, and P2 form the first gain stage of the
differential amplifier. A1 and A2 are auto-zeroed op amps that
minimize input offset errors. P1 and P2 are digital potentiome-
ters, guaranteed to be monotonic. Programming P1 and P2
allows the first stage gain to be varied from 4.0 to 6.4 with 7-bit
resolution (see Table 6 and Equation 3), giving a fine gain
adjustment resolution of 0.37%. R1, R2, R3, P1, and P2 each
have a similar temperature coefficient, so the first stage gain
temperature coefficient is lower than 100 ppm/°C.
Rev. 0 | Page 17 of 28
A3, R4, R5, R6, R7, P3, and P4 form the second gain stage of the
differential amplifier. A3 is also an auto-zeroed op amp that
minimize input offset errors. P3 and P4 are digital potentiome-
ters, allowing the second stage gain to be varied from 17.5 to
200 in eight steps (see Table 7); they allow the gain to be varied
over a wide range. R4, R5, R6, R7, P3, and P4 each have a similar
temperature coefficient, so the second stage gain temperature
coefficient is lower than 100 ppm/°C.
RF together with an external capacitor connected between
FILT/DIGOUT and VSS or VDD form a low-pass filter. The
filtered signal is buffered by A4 to give a low impedance output
at VOUT. RF is nominally 16 k, allowing a 1 kHz low-pass
filter to be implemented by connecting a 10 nF external
capacitor between FILT/DIGOUT and VSS or between
FILT/DIGOUT and VDD. If low-pass filtering is not needed,
then the FILT/DIGOUT pin must be left floating.
A5 implements a voltage buffer, which provides the positive
supply to the amplifier output buffer A4. Its function is to limit
VOUT to a maximum value, useful for driving analog-to-digital
converters (ADC) operating on supply voltages lower than
VDD. The input to A5, VCLAMP, has a very high input resis-
tance. It should be connected to a known voltage and not left
floating. However, the high input impedance allows the clamp
voltage to be set using a high impedance source, e.g., a potential
divider. If the maximum value of VOUT does not need to be
limited, VCLAMP should be connected to VDD.
A4 implements a rail-to-rail input and output unity-gain volt-
age buffer. The output stage of A4 is supplied from a buffered
version of VCLAMP instead of VDD, allowing the positive
swing to be limited. The maximum output current is limited
between 5 mA to 10 mA.
An 8-bit digital-to-analog converter (DAC) is used to generate a
variable offset for the amplifier output. This DAC is guaranteed
to be monotonic. To preserve the ratiometric nature of the input
signal, the DAC references are driven from VSS and VDD, and
the DAC output can swing from VSS (Code 0) to VDD (Code
255). The 8-bit resolution is equivalent to 0.39% of the differ-
ence between VDD and VSS, e.g., 19.5 mV with a 5 V supply.
The DAC output voltage (VDAC) is given approximately by
(
)
VSS
+
VSS
VDD
Code
VDAC
+
≈
256
5
(1)
The temperature coefficient of VDAC is lower than
200 ppm/°C.
The amplifier output voltage (VOUT) is given by
(
)
VDAC
+
VNEG
VPOS
GAIN
VOUT
=
(2)
where
GAIN
is the product of the first and second stage gains.
A3
A2
A4
A5
VDD
VDD
DAC
VSS
VSS
VDD
VSS
VDD
VDD
VSS
VCLAMP
VPOS
VSS
FILT/
DIGOUT
VOUT
A1
VDD
VSS
VNEG
R1
R3
R2
R5
R7
P4
R4
R6
RF
P3
P2
P1
0
Figure 49. AD8555 Functional Schematic
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| AD8555ACP-R2 | Zero-Drift, Digitally Programmable Sensor Signal Amplifier |
| AD8555ACP-REEL | Zero-Drift, Digitally Programmable Sensor Signal Amplifier |
| AD8561AR | Ultrafast 7 ns Single Supply Comparator |
| AD8561ARU | Ultrafast 7 ns Single Supply Comparator |
| AD8561AN | Ultrafast 7 ns Single Supply Comparator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8555_09 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Zero-Drift, Digitally Programmable Sensor Signal Amplifier |
| AD85551 | 制造商:AD 制造商全稱:Analog Devices 功能描述:10 MHz, 20 V/レs, G = 1, 10, 100, 1000 i CMOS㈢ Programmable Gain Instrumentation Amplifier |
| AD8555ACP | 制造商:Analog Devices 功能描述:SP AMP CURRENT SENSE AMP SGL R-R I/O 5.5V 16LFCSP EP - Bulk |
| AD8555ACP-R2 | 制造商:Analog Devices 功能描述:SP Amp Current Sense Amp Single R-R I/O 5.5V 16-Pin LFCSP EP T/R 制造商:Rochester Electronics LLC 功能描述:AUTO ZERO AMP W/PROGRAMMABLE GAIN/OFFSET - Bulk |
| AD8555ACP-REEL | 制造商:Analog Devices 功能描述:SP Amp Current Sense Amp Single R-R I/O 5.5V 16-Pin LFCSP EP T/R |
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