AD7715AR-5 (Analog) PDF资料下载 Datasheet(31/40 页)

您好，
买卖IC网欢迎您。
请登录
免费注册

您现在的位置：买卖IC网 > PDF目录10231 > AD7715AR-5 (Analog Devices Inc)IC ADC 16BIT 5V 16-SOIC PDF资料下载

参数资料

型号：	AD7715AR-5
厂商：	Analog Devices Inc
文件页数：	31/40页
文件大小：	0K
描述：	IC ADC 16BIT 5V 16-SOIC
标准包装：	47
位数：	16
采样率（每秒）：	500
数据接口：	DSP，MICROWIRE?，QSPI?，串行，SPI?
转换器数目：	1
功率耗散（最大）：	9.5mW
电压电源：	模拟和数字
工作温度：	-40°C ~ 85°C
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
输入数目和类型：	1 个差分，单极；1 个差分，双极
配用：	EVAL-AD7715-3EBZ-ND - BOARD EVALUATION FOR AD7715

AD7715

Rev. D | Page 37 of 40

TEMPERATURE MEASUREMENT

Another application area for the AD7715 is in temperature

measurement. Figure 15 outlines a connection from a thermo-

couple to the AD7715. In this application, the AD7715 is operated

in its buffered mode to allow large decoupling capacitors on the

front end to eliminate any noise pickup that there may have

been in the thermocouple leads. When the AD7715 is operated

in buffered mode, it has a reduced common-mode range. To place

the differential voltage from the thermocouple on a suitable

common-mode voltage, the AIN() input of the AD7715 is

biased up at the reference voltage, 2.5 V.

Figure 16 shows another temperature measurement application

for the AD7715. In this case, the transducer is an resistive tem-

perature device (RTD), a PT100. The arrangement is a 4-lead

RTD configuration. There are voltage drops across the lead

resistances RL1 and RL4, but these simply shift the common-

mode voltage. There is no voltage drop across lead resistances

RL2 and RL3 as the input current to the AD7715 is very low. The

lead resistances present a small source impedance so it would

not generally be necessary to turn on the buffer on the AD7715.

If the buffer is required, the common-mode voltage should be

set accordingly by inserting a small resistance between the bottom

end of the RTD and AGND of the AD7715. In the application

shown in Figure 16, an external 400 μA current source provides

the excitation current for the PT100 and it also generates the

reference voltage for the AD7715 via the 6.25 kΩ resistor. Varia-

tions in the excitation current do not affect the circuit as both the

input voltage and the reference voltage vary ratiometrically with

the excitation current. However, the 6.25 kΩ resistor must have

a low temperature coefficient to avoid errors in the reference

voltage over temperature.

SERIAL INTERFACE

MCLK IN

MCLK OUT

REF IN(+)

REF IN(–)

AGND

DGND

DOUT

DIN

SCLK

AD7715

AIN(+)

AIN(–)

A = 1 TO 128

PGA

BUFFER

CLOCK

GENERATION

GND

VOUT

REF192

THERMOCOUPLE

JUNCTION

+5V

+VIN

AUTO-ZEROED

Σ-

MODULATOR

CHARGE BALANCING ADC

DIGITAL

FILTER

AVDD

REGISTER BANK

DRDY

RESET

DVDD

Figure 15. Thermocouple Measurement Using the AD7715