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参数资料
| 型号： | AD7740YRTZ-REEL7 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 10/11页 |
| 文件大小： | 144K |
| 描述： | IC CONVERTER VOLT-FREQ SOT23-8 |
| 标准包装： | 1 |
| 类型： | 电压至频率 |
| 频率 - 最大： | 1MHz |
| 全量程： | ±50ppm/°C |
| 线性： | ±0.012% |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SOT-23-8 |
| 供应商设备封装： | SOT-23-8 |
| 包装： | 标准包装 |
| 其它名称： | AD7740YRTZ-REEL7DKR |
10
Temperature Sensor Application
The AD7740 can be used with an AD22100S temperature
sensor to give a digital measure of ambient temperature. The
output voltage of the AD22100S is proportional to the tempera-
ture times the supply voltage. It uses a single 5 V supply, and its
output swings from 0.25 V at 50癈 to 4.75 V at +150癈. By
feeding its output through the AD7740, the value of ambient
temperature is converted into a digital pulse train. See Figure 12.
REFIN
AD7740
AD22100S
V+
CLKIN CLKOUT
C1
C2
FOUT
GND
BUF
0.1F
10F
0.1F
VIN
VDD
5V
10F
Figure 12. Using the AD7740 with a Temperature Sensor
Due to its ratiometric nature this application provides an
extremely cost-effective solution. The need for an external pre-
cision reference is eliminated since the 5 V power-supply is used
as a reference to both the VFC and the AD22100S.
32 kHz Operation
The AD7740 oscillator circuit will not operate at 32 kHz. If
the user wishes to use a 32 kHz watch crystal, some additional
external circuitry is required. The circuit in Figure 13 is for a
crystal with a required drive of 1 礧. Resistors R1 and R2
reduce the power to this level.
R3
1M
CLKIN
R2
100k
R1
220k
32kHz
40106
40106
Figure 13. 32 kHz Watch Crystal Circuit
Power Supply Bypassing and Grounding
In any circuit where accuracy is important, careful consideration
of the power supply and ground return layout helps to ensure
the rated performance. The printed circuit board housing the
AD7740 should be designed such that the analog and digital
sections are separated and conned to certain areas of the board.
To minimize capacitive coupling between them, digital and
analog ground planes should only be joined in one place, close
to the AD7740, and should not overlap.
Avoid running digital lines under the device, as these will couple
noise onto the die. The analog ground plane should be allowed
to run under the AD7740 to avoid noise coupling. The power
supply lines to the AD7740 should use as large a trace as pos-
sible to provide low impedance paths and reduce the effects of
glitches on the power supply line. Fast switching signals like
clocks should be shielded with digital ground to avoid radiating
noise to other parts of the board, and clock signals should never
be run near analog inputs. Avoid crossover of digital and analog
signals. Traces on opposite sides of the board should run at right
angles to each other. This reduces the effect of feedthrough
through the board. A microstrip technique is by far the best but
is not always possible with a double-sided board. In this technique,
the component side of the board is dedicated to the ground plane
while the signal traces are placed on the solder side.
Good decoupling is also important. All analog supplies should
be decoupled to GND with surface mount capacitors, 10 礔 in
parallel with 0.1 礔 located as close to the package as possible,
ideally right up against the device. The lead lengths on the by-
pass capacitor should be as short as possible. It is essential that
these capacitors be placed physically close to the AD7740 to
minimize the inductance of the PCB trace between the capacitor
and the supply pin. The 10 礔 are the tantalum bead type and
are located in the vicinity of the VFC to reduce low-frequency
ripple. The 0.1 礔 capacitors should have low Effective Series
Resistance (ESR) and Effective Series Inductance (ESI), such
as the common ceramic types, which provide a low imped-
ance path to ground at high frequencies to handle transient
currents due to internal logic switching. Additionally, it is ben-
ecial to have large capacitors (> 47 礔) located at the point
where the power connects to the PCB.
AD7740
REV. A
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD7741 | 制造商:AD 制造商全称:Analog Devices 功能描述:Single and Multichannel, Synchronous Voltage-to-Frequency Converters |
| AD7741BN | 制造商:Analog Devices 功能描述:VFC Sync 1.35MHz 8-Pin PDIP Tube 制造商:Rochester Electronics LLC 功能描述:SINGLE + MULTI-CHANNEL VFC I.C. - Bulk 制造商:Analog Devices 功能描述:IC VOLTAGE-FREQ CONVERTER |
| AD7741BNZ | 功能描述:IC CONVERTER VOLT TO FREQ 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 |
| AD7741BR | 功能描述:IC CONVERTER V TO FREQ 8-SOIC 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 |
| AD7741BR-REEL | 功能描述:IC CONVERTER V TO FREQ 8-SOIC 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 |
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