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| 型号： | AD8436ACPZ-R7 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 14/24页 |
| 文件大小： | 0K |
| 描述： | IC CONV TRUE RMS-DC LP 20LFCSP |
| 产品培训模块： | Introduction to Analog RMS-to-DC Technology: Converters and Applications |
| 标准包装： | 1 |
| 电流 - 电源： | 325µA |
| 电源电压： | ±2.4 V ~ 18 V，4.8 V ~ 36 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-WFQFN 裸露焊盘，CSP |
| 供应商设备封装： | 20-LFCSP-WQ（4x4） |
| 包装： | 标准包装 |
| 其它名称： | AD8436ACPZ-R7DKR |
AD8436
capacitor of 0.1 μF and an averaging capacitor of 10 μF. The
larger capacitor serves to average the energy over long spaces
between pulses, while the CCF capacitor charges and holds the
energy within the relatively narrow pulse.
Using the FET Input Buffer
The on-chip FET input buffer is an uncommitted FET input
op amp used for driving the 8 k? I-to-V input resistor of the
rms core. Pin IBUFOUT, Pin IBUFIN?, and Pin IBUFIN+ are
the I/O, Pin IBUFINGN is an optional connection for gain in
the input buffer, and Pin IBUFV+ connects power to the
buffer. Connecting Pin IBUFV+ to the positive rail is the
only power connection required because the negative rail is
internally connected. Because the input stage is a FET and
the input impedance must be very high to prevent loading
of the source, a large value (10 M?) resistor is connected from
midsupply at Pin IGND to Pin IBUFIN+ to prevent the input
gate from floating high.
For unity gain, connect the IBUFOUT pin to the IBUFIN? pin.
and Figure 10 for large and small signal responses at the two
built-in gain options.
The offset voltage of the input buffer is ≤500 μV, depending on
grade. A capacitor connected between the buffer output pin
(IBUFOUT) and the RMS pin is recommended so that the
input buffer offset voltage does not contribute to the overall
error. Select the capacitor value for least minimum error at the
Data Sheet
Because the 10 kΩ resistors are closely matched and trimmed to
a high tolerance, the input buffer gain can be increased to several
hundred with an external resistor connected to Pin IBUFIN?.
The bandwidth diminishes at the typical rate of a decade per 20 dB
of gain, and the output voltage range is constrained. The small
signal response, shown in Figure 9, serves as a guide. For example,
suppose one wanted to detect small input signals at power line
frequencies? An external 10 ? resistor connected from IBUFIN? to
ground sets the gain to 101 and the 3 dB bandwidth to ~30 kHz,
which is more than adequate for amplifying power line frequencies.
Using the Output Buffer
The AD8436 output buffer is a precision op amp optimized for
high dc accuracy. Figure 34 shows a block diagram of the basic
amplifier and I/O pins. The amplifier is often configured as a unity
gain follower but is easily configured for gain, as a Sallen-Key low-
pass filter (in conjunction with the built-in 16 kΩ I-to-V resistor).
Note that an additional 16 k? on-chip precision resistor in series
with the inverting input of the amplifier balances output offset
voltages resulting from the bias current from the noninverting
amplifier. The output buffer is disconnected from Pin OUT for
precision core measurements.
As with the input FET buffer, the amplifier positive supply is
disconnected when not needed. In normal circumstances, the
shows the signal connections to the output buffer. Note that
the input offset voltage contribution by the bias currents are
balanced by equal value series resistors, resulting in near zero
lowest operating frequency. Figure 33 is a schematic showing
internal components and pin connections.
16
offset voltage.
OBUFIN+
OUTPUT BUFFER
+
2 RMS
IBUFV+
OBUFIN–
16k?
–
OBUFOUT
10μF
3
4
IBUFOUT
IBUFIN–
–
Figure 34. Output Buffer Block Diagram
0.47μF
5
IBUFIN+
+
10k?
CORE
OUT
9
IBIAS
12
OBUFIN+
+
OBUFOUT
10M?
10pF
16k?
13
16k?
–
14
11 IGND
OBUFIN–
6
10k?
OGND
8
IBUFGN
Figure 33. Connecting the FET Input Buffer
Capacitor coupling at the input and output of the FET buffer is
recommended to avoid transferring the buffer offset voltage to
the output. Although the FET input impedance is extremely high,
the 10 MΩ centering resistor connected to IGND must be taken
into account when selecting an input capacitor value. This is simply
an impedance calculation using the lowest desired frequency,
and finding a capacitor value based on the least attenuation desired.
Figure 35. Basic Output Buffer Connections
For applications requiring ripple suppression in addition to the
single-pole output filter described previously, the output buffer
is configurable as a two-pole Sallen-Key filter using two external
resistors and two capacitors. At just over 100 kHz, the amplifier
has enough bandwidth to function as an active filter for low
frequencies such as power line ripple. For a modest savings in
cost and complexity, the external 16 kΩ feedback resistor can be
omitted, resulting in slightly higher V OS (80 μV).
Rev. B | Page 14 of 24
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8436ACPZ-R7_PROMO | 制造商:Analog Devices 功能描述:RMS-DC CONVERTER 1MHZ 325UA |
| AD8436ACPZ-RL | 功能描述:IC CONV TRUE RMS-DC LP 20LFCSP RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| AD8436ACPZ-WP | 功能描述:IC CONV TRUE RMS-DC LP 20LFCSP RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| AD8436ARQZ | 功能描述:IC CONV TRUE RMS-DC LP 20QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| AD8436ARQZ_PROMO | 制造商:Analog Devices 功能描述:IC RMS TO DC CONV 0.5% QSOP |
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