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| 型号： | AD652SQ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 16/28页 |
| 文件大小： | 779K |
| 描述： | IC V-F CONV SYNCH MONO 5V 16CDIP |
| 标准包装： | 1 |
| 类型： | 电压至频率 |
| 频率 - 最大： | 2MHz |
| 全量程： | ±25ppm/°C |
| 线性： | ±0.005% |
| 安装类型： | 通孔 |
| 封装/外壳： | 16-CDIP（0.300"，7.62mm） |
| 供应商设备封装： | 16-CDIP |
| 包装： | 管件 |
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AD652
Rev. C | Page 16 of 28
DECOUPLING AND GROUNDING
It is good engineering practice to use bypass capacitors on the
supply-voltage pins, and to insert small valued resistors (10 & to
100 &) in the supply lines to provide a measure of decoupling
between the various circuits in a system. Ceramic capacitors of
0.1 礔 to 1.0 礔 should be applied between the supply voltage
pins and analog signal ground for proper bypassing on the
AD652.
Additionally, a larger board-level decoupling capacitor of 1 礔
to 10 礔 should be located relatively close to the AD652 on each
power supply line. Such precautions are imperative in high
resolution data acquisition applications where one expects to
exploit the full linearity and dynamic range of the AD652.
Separate digital and analog grounds are provided on the AD652.
Only the emitter of the open-collector frequency output
transistor and the clock input threshold are returned to the
digital ground. Only the 5 V reference is connected to analog
ground. The purpose of the two separate grounds is to allow
isolation between the high precision analog signals and the
digital section of the circuitry. Much noise can be tolerated on
the digital ground without affecting the accuracy of the VFC.
Such ground noise is inevitable when switching the large
currents associated with the frequency output signal.
At high full-scale frequencies, it is necessary to use a pull-up
resistor of about 500 & in order to get the rise time fast enough
to provide well-defined output pulses. This means that from a
5 V logic supply, for example, the open collector output draws
10 mA. This much current being switched causes ringing on
long ground runs due to the self-inductance of the wires. For
instance, 20-gauge wire has an inductance of about 20 nH per
inch; a current of 10 mA being switched in 50 ns at the end of
12 inches of 20-gauge wire produces a voltage spike of 50 mV.
The separate digital ground of the AD652 easily handles these
types of switching transients.
A problem remains from interference caused by radiation of
electromagnetic energy from these fast transients. Typically, a
voltage spike is produced by inductive switching transients;
these spikes can capacitively couple into other sections of the
circuit. Another problem is ringing of ground lines and power
supply lines due to the distributed capacitance and inductance
of the wires. Such ringing can also couple interference into
sensitive analog circuits. The best solution to these problems is
proper bypassing of the logic supply at the AD652 package. A
1 礔 to 10 礔 tantalum capacitor should be connected directly
to the supply side of the pull-up resistor and to the digital
ground, Pin 12. The pull-up resistor should be connected
directly to the frequency output, Pin 11. The lead lengths on the
bypass capacitor and the pull-up resistor should be as short as
possible. The capacitor supplies (or absorbs) the current
transients, and large ac signals flow in a physically small loop
through the capacitor, pull-up resistor, and frequency output
transistor. It is important that the loop be physically small for
two reasons: first, there is less inductance if the wires are short,
and second, the loop does not radiate RFI efficiently.
The digital ground (Pin 12) should be separately connected to
the power supply ground. Note that the leads to the digital
power supply are only carrying dc current. There may be a dc
ground drop due to the difference in currents returned on the
analog and digital grounds. This does not cause a problem;
these features greatly ease power distribution and ground
manage-ment in large systems. The proper technique for
grounding requires separate digital and analog ground returns
to the power supply. Also, the signal ground must be referred
directly to the analog ground (Pin 6) at the package. More
information on proper grounding and reduction of interference
can be found in Noise Reduction Techniques in Electronic
Systems, by H.W. Ort, (John Wiley, 1976).
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD652SQ/883B | 功能描述:电压频率转换及频率电压转换 IC - SYNC V/F CONVERTER RoHS:否 制造商:Texas Instruments 全标度频率:4000 KHz 线性误差:+/- 1 % FSR 电源电压-最大: 电源电压-最小: 最大工作温度:+ 85 C 最小工作温度:- 25 C 安装风格:Through Hole 封装 / 箱体:PDIP-14 封装:Tube |
| AD652SQ/883B2 | 制造商:AD 制造商全称:Analog Devices 功能描述:Monolithic Synchronous Voltage-to-Frequency Converter |
| AD652SQ2 | 制造商:AD 制造商全称:Analog Devices 功能描述:Monolithic Synchronous Voltage-to-Frequency Converter |
| AD652SQ883B2 | 制造商:AD 制造商全称:Analog Devices 功能描述:Monolithic Synchronous Voltage-to-Frequency Converter |
| AD652SW | 制造商:AD 制造商全称:Analog Devices 功能描述:Monolithic Synchronous Voltage-to-Frequency Converter |
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