Datasheet > AD7740KRM-REEL

AD7740KRM-REEL

更新时间： 2024-02-27 01:42:50

品牌	Logo	应用领域
亚德诺 - ADI		光电二极管转换器
页数	文件大小	规格书
2页	50K
描述
IC VOLTAGE-FREQUENCY CONVERTER, 1 MHz, PDSO8, MICRO, SOIC-8, Analog Special Function Converter

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技术参数
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AD7740KRM-REEL 技术参数

是否Rohs认证：	不符合	生命周期：	Obsolete
零件包装代码：	SOIC	包装说明：	TSSOP, TSSOP8,.19
针数：	8	Reach Compliance Code：	not_compliant
ECCN代码：	EAR99	HTS代码：	8542.39.00.01
风险等级：	5.12	其他特性：	CAN ALSO OPERATE FROM 4.75V TO 5.25V SUPPLY
转换器类型：	VOLTAGE TO FREQUENCY CONVERTER	JESD-30 代码：	R-PDSO-G8
JESD-609代码：	e0	长度：	3 mm
最大线性误差 (EL)：	0.018%	湿度敏感等级：	1
功能数量：	1	端子数量：	8
最大工作频率：	1 MHz	最高工作温度：	85 °C
最低工作温度：		封装主体材料：	PLASTIC/EPOXY
封装代码：	TSSOP	封装等效代码：	TSSOP8,.19
封装形状：	RECTANGULAR	封装形式：	SMALL OUTLINE, THIN PROFILE, SHRINK PITCH
峰值回流温度（摄氏度）：	240	最大正输入电压：	3.1 V
电源：	3.3/5 V	认证状态：	Not Qualified
座面最大高度：	1.1 mm	子类别：	Analog Special Function Converters
最大压摆率：	1.5 mA	最大供电电压：	3.6 V
最小供电电压：	3 V	标称供电电压：	3.3 V
表面贴装：	YES	技术：	CMOS
温度等级：	OTHER	端子面层：	Tin/Lead (Sn85Pb15)
端子形式：	GULL WING	端子节距：	0.65 mm
端子位置：	DUAL	处于峰值回流温度下的最长时间：	30
宽度：	3 mm	Base Number Matches：	1

AD7740KRM-REEL 数据手册

2/10/00

TECHNICAL NOTE

OneTechnologyWay•P.O. Box9106•Norwood, MA02062-9106•781/329-4700•WorldWideWebSite:http://www.analog.com

Using the AD7740 in Isolation Applications

By Helen Stapleton

IN TRO D U C TIO N

In low-power circuits the AD7740 is typically clocked at

32 kHz. This corresponds to an output frequency of 3.2

kHz to 28.8 kHz for a nom inal input voltage range of 0 V

to 5 V on VIN. Hence the optocoupler used m ust have

rise- and fall-tim es which can accom m odate this fre-

quency range.

This Technical Note describes how to use an AD7740

Voltage-to-Frequency Converter in an isolated applica-

tion. Due to noise, safety requirem ents or distance it

m ay be required to isolate the AD7740 from any control-

ling circuitry. This can be easily achieved by using

optocouplers, which can provide isolation in excess of

5kV.

A disadvantage of this approach is that logic-gate

optocouplers tend to be quite expensive. Another ap-

proach is to use som e additional circuitry to speed up a

cheap and slow optocoupler. By using a differential line-

driver (e.g. ADM485) the m axim um frequency through

the optocoupler can be increased by a factor of six. See

Figure 2.

The VFC converts the analog voltage to be transm itted,

VIN, to a digital pulse train. An optocoupler circuit is

used to couple this pulse train across an isolation bar-

rier using light as the connecting m edium . The input

LED of the isolator is driven from the output of the

AD7740. At the receiver side, the output transistor is op-

erated in the photo-transistor m ode. The pulse train is

inverted and can be reconverted to an analog voltage

using a frequency-to-voltage converter; alternatively,

the pulse train can be fed into a counter to generate a

digital signal.

0.1µF

10µF

PS2502-2

VIN

FOUT

The analog and digital sections of the AD7740 have

been designed to allow operation from a single-ended

power source, sim plifying its use with isolated power

supplies.

AD7740

GND1

ADM 485

GND2

ISOLATION

BARRIER

0.1µF

10µF

FOUT

Figure 2. Using a differential line-driver to speed up an

optocoupler

VIN

FOUT

OPTO COUPLER

The scope plots in Figures 3 and 4 overleaf show that

the m axim um frequency through the PS2502-2

optocoupler has been increased from 5 kHz to 32 kHz by

the addition of a differential line-driver. Hence this cir-

cuit can handle the full FOUT range thus providing a

low-cost solution to signal isolation.

AD7740

GND1

GND2

ISOLATION

BARRIER

Figure 1. AD7740 in an Opto-Isolated Application

Figure 1 shows the AD7740 in an application where iso-

lation is achieved using a logic-gate optocoupler. A +5 V

power supply is assum ed for both the isolated (V_DD) and

local (V_CC) supplies.

When the reference pin (REFIN) is tied to V_DDthe trans-

fer-function of the AD7740 is:

FOUT = 0.1 CLKIN + 0.8 (VIN/REFIN) CLKIN

REV. 0

–1–

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与AD7740KRM-REEL相关器件

型号	品牌	获取价格	描述	数据表
AD7740KRMZ	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740KRMZ-REEL	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740KRMZ-REEL7	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740YRM	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740YRM-REEL7	ADI	获取价格	VOLTAGE-FREQUENCY CONVERTER, 1MHz, PDSO8, MICRO, SOIC-8
AD7740YRMZ	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740YRMZ-REEL	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740YRMZ-REEL7	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740YRT	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter
AD7740YRTZ-REEL7	ADI	获取价格	3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter

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