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| 型号： | AD654 |
| 厂商： | Analog Devices, Inc. |
| 英文描述： | Low Cost Monolithic Voltage-to-Frequency Converter(低成本单片电压-频率转换器) |
| 中文描述： | 低成本单片电压频率转换器（低成本单片电压-频率转换器） |
| 文件页数： | 5/8页 |
| 文件大小： | 307K |
| 代理商： | AD654 |
AD654
REV. A
–5–
shown in Figure 5. It is also desirable not to drive +V
IN
and R
T
above +V
S
. In operation, the converter will exhibit a zero output
for inputs above (+V
S
– 3.5 V). Also, control currents above
2 mA will increase nonlinearity.
The AD654’s 80 dB dynamic range guarantees operation from a
control current of 1 mA (nominal FS) down to 100 nA (equiva-
lent to 1 mV to 10 V FS). Below 100 nA improper operation of
the oscillator may result, causing a false indication of input am-
plitude. In many cases this might be due to short-lived noise
spikes which become added to input. For example, when scaled
to accept an FS input of 1 V, the –80 dB level is only 100
μ
V, so
when the mean input is only 60 dB below FS (1 mV), noise
spikes of 0.9 mV are sufficient to cause momentary malfunction.
This effect can be minimized by using a simple low-pass filter
ahead of the converter or a guard ring around the R
T
pin. The
filter can be assembled using the bias current compensation
resistor discussed in the previous section. For an FS of 10 kHz,
a single-pole filter with a time constant of 100 ms will be suit-
able, but the optimum configuration will depend on the applica-
tion and the type of signal processing. Noise spikes are only
likely to be a cause of error when the input current remains near
its minimum value for long periods of time; above 100 nA full
integration of additive input noise occurs. Like the inputs, the
capacitor terminals are sensitive to interference from other sig-
nals. The timing capacitor should be located as close as possible
to the AD654 to minimize signal pickup in the leads. In some
cases, guard rings or shielding may be required.
DECOUPLING
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
Figure 5. Input Protection
between the various circuits in the system. Ceramic capacitors
of 0.1
μ
F to 1.0
μ
F should be applied between the supply-voltage
pins and analog signal ground for proper bypassing on the AD654.
A proper ground scheme appears in Figure 6.
Figure 6. Proper Ground Scheme
OUTPUT INTERFACING CONSIDERATION
The output stage’s design allows easy interfacing to all digital
logic families. The output NPN transistor’s emitter and collec-
tor are both uncommitted. The emitter can be tied to any volt-
age between –V
S
and 4 volts below +V
S
, and the open collector
can be pulled up to a voltage 36 volts above the emitter regard-
less of +V
S
. The high power output stage can sink over 10 mA
at a maximum saturation voltage of 0.4 V. The stage limits the
output current at 25 mA and can handle this limit indefinitely
without damaging the device.
NONLINEARITY SPECIFICATION
The preferred method of specifying nonlinearity error is in terms
of maximum deviation from the ideal relationship after calibrat-
ing the converter at full scale. This error will vary with the full
scale frequency and the mode of operation. The AD654 oper-
ates best at a 150 kHz full-scale frequency with a negative
voltage input; the linearity is typically within 0.05%. Operating
at higher frequencies or with positive inputs will degrade the lin-
earity as indicated in the Specifications Table. Typical linearity
at various temperatures is shown in Figure 7.
TWO-WIRE TEMPERATURE-TO-FREQUENCY
CONVERSION
Figure 8 shows the AD654 in a two-wire temperature-to-frequency
conversion scheme. The twisted pair transmission line serves the
dual purpose of supplying power to the device and also carrying
frequency data in the form of current modulation.
The positive supply line is fed to the remote V/F through a
140
resistor. This resistor is selected such that the quiescent
current of the AD654 will cause less than one V
BE
to be dropped.
Figure 7. Typical Nonlinearities at Different Full-Scale
Frequencies
Figure 8. Two-Wire Temperature-to-Frequency Converter
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD654JCHIPS | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Voltage-to-Frequency Converter |
| AD654JN | 功能描述:IC V-F CONVERTER MONO 8-DIP RoHS:否 类别:集成电路 (IC) >> PMIC - V/F 和 F/V 转换器 系列:- 标准包装:1 系列:- 类型:频率至电压 频率 - 最大:10kHz 全量程:- 线性:±0.3% 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:Digi-Reel® 其它名称:LM2917MX-8/NOPBDKR |
| AD654JN/+ | 制造商:Rochester Electronics LLC 功能描述:IC - LOW COST V/F CONV. - Bulk |
| AD654JNZ | 功能描述:IC V-F CONVERTER MONO 8-DIP RoHS:是 类别:集成电路 (IC) >> PMIC - V/F 和 F/V 转换器 系列:- 标准包装:1 系列:- 类型:频率至电压 频率 - 最大:10kHz 全量程:- 线性:±0.3% 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:Digi-Reel® 其它名称:LM2917MX-8/NOPBDKR |
| AD654JNZ/+ | 功能描述:IC CONV VOLT-FREQ 500KHZ 8DIP RoHS:是 类别:集成电路 (IC) >> PMIC - V/F 和 F/V 转换器 系列:- 标准包装:1 系列:- 类型:频率至电压 频率 - 最大:10kHz 全量程:- 线性:±0.3% 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:Digi-Reel® 其它名称:LM2917MX-8/NOPBDKR |
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