参数资料
| 型号： | AD7191BRUZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 9/21页 |
| 文件大小： | 0K |
| 描述： | IC ADC 2CH 24B SD 24TSSOP |
| 产品培训模块： | Weigh Scale Introduction |
| 设计资源： | Precision Weigh Scale Design Using AD7191 with Internal PGA (CN0118) |
| 标准包装： | 62 |
| 位数： | 24 |
| 采样率（每秒）： | 120 |
| 数据接口： | MICROWIRE?，QSPI?，串行，SPI? |
| 转换器数目： | 1 |
| 电压电源： | 模拟和数字 |
| 工作温度： | -40°C ~ 105°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 24-TSSOP |
| 包装： | 管件 |
| 输入数目和类型： | 2 个差分，双极 |
| 产品目录页面： | 777 (CN2011-ZH PDF) |
AD7191
Rev. A | Page 16 of 20
TEMPERATURE SENSOR
Embedded in the AD7191 is a temperature sensor. The
temperature sensor is selected when the TEMP pin is tied
high. The TEMP pin has higher priority than the CHAN
pin; therefore, when TEMP is high, the temperature sensor
is selected irrespective of the polarity on the CHAN pin.
When the temperature sensor is selected, the device should
return a code of 0x800000 when the temperature is 0 K. A one-
point calibration is needed to get the optimum performance from
the sensor. Therefore, a conversion at 25°C should be recorded
and the sensitivity calculated. The sensitivity is 2815 codes/°C,
approximately. The equation for the temperature sensor is
Temp (K) = (Conversion 0x800000)/2815 K
Temp (°C) = Temp (K) 273
Following the one point calibration, the internal temperature
sensor has an accuracy of ±2°C, typically.
Each time the temperature sensor is selected, DOUT/RDY goes
high and remains high until the appropriate settling time
elapses. Therefore, any read operations should be completed
before selecting the temperature sensor. Otherwise, all 1s are
read back from the AD7191 as the DOUT/RDY pin is set high
following the channel change.
POWER-DOWN (PDOWN)
The PDOWN pin functions as a power-down pin and a reset
pin. When PDOWN is taken high, the AD7191 is powered
down and the DOUT/RDY pin is tristated. If the on-chip clock
is selected, it will be powered down also. If an external crystal is
being used, the on-chip oscillator circuitry remains active.
With PDOWN high, the circuitry and serial interface are also
reset. This resets the logic, the digital filter, and the analog
modulator. PDOWN must be held high for 100 ns minimum to
initiate the reset function.
When PDOWN is taken low, the AD7191 is taken out of power-
down mode. When the on-chip clock has powered up (1 ms,
typically), the modulator begins sampling the analog input, and
the DOUT/RDY pin becomes active. When an external crystal
or clock is used as the master clock source to the AD7191, the
1 ms power-up time is not required. A reset is automatically
performed on power-up.
CLOCK
The AD7191 has an internal 4.92 MHz clock that has a 4%
tolerance. The AD7191 can use the internal clock or, alterna-
tively, an external clock or crystal can be used. The CLKSEL
pin is used to select the clock source. When CLKSEL is low,
an external clock/crystal is selected. When CLKSEL is high,
the internal clock is selected. If a crystal is used, the crystal
should be connected between MCLK1 and MCLK2. The user
should refer to the crystal data sheet for details on the capacitor
values. If an external clock source is used, it should be applied
to MCLK1. MCLK2 should be left unconnected.
When the polarity of CLKSEL is changed, DOUT/RDY goes
high and remains high until the appropriate settling time elapses.
BIPOLAR CONFIGURATION
The AD7191 accepts a bipolar input range. A bipolar input
range does not imply that the part can tolerate negative voltages
with respect to system AGND. Signals on the positive analog
input pin are referenced to the voltage on the negative analog
input pin. For example, if AIN2 is 2.5 V, the analog input range
on the AIN1 input is 2.461 V to 2.539 V for a gain of 128 when
a 5 V reference is used.
DATA OUTPUT CODING
The AD7191 uses offset binary coding. Therefore, a negative
full-scale voltage results in a code of 000...000, a zero differen-
tial input voltage results in a code of 100...000, and a positive
full-scale input voltage results in a code of 111...111. The output
code for any analog input voltage can be represented as
Code = 2N – 1 × [(AIN × Gain/VREF) + 1]
where AIN is the analog input voltage (AIN1 – AIN2 or AIN3 –
AIN4), Gain is 1, 8, 64, or 128, and N = 24 for the AD7191.
BRIDGE POWER-DOWN SWITCH
The bridge power-down switch (BPDSW) is useful in battery-
powered applications where it is essential that the power
consumption of the system be optimized. A 350 Ω load cell
consumes 15 mA typically when excited with a 5 V power
supply. To minimize the current consumption, the load cell is
disconnected when it is not being used. The bridge power-
down switch can be included in series with the load cell. When
PDOWN is low, the bridge power-down switch is closed, and
the load cell measures the strain. When PDOWN is high, the
bridge power-down switch is opened so that no current flows
through the load cell. Therefore, the current consumption of
the system is minimized. The bridge power-down switch has an
on-resistance of 10 Ω maximum, and it is capable of
withstanding 30 mA of continuous current.
REFERENCE
The AD7191 has a fully differential input capability. The
common-mode range for these differential inputs is AGND to
AVDD. The reference input is unbuffered; therefore, excessive
R-C source impedances introduce gain errors. The reference
voltage REFIN (REFIN(+) REFIN()) is AVDD nominal, but
the AD7191 is functional with reference voltages of 1 V to AVDD.
In applications where the excitation (voltage or current) of the
transducer connected to the analog input also drives the refer-
ence voltage for the part, the effect of the low frequency noise in
the excitation source is removed because the application is ratio-
metric. If the AD7191 is used in a nonratiometric application,
a low noise reference should be used.
Recommended 2.5 V reference voltage sources for the AD7191
include the ADR421, which is a low noise reference. These
references have low output impedances and are, therefore,
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| AD7191BRUZ | 制造商:Analog Devices 功能描述:IC ADC 24BIT 120SPS TSSOP-24 |
| AD7191BRUZ-REEL | 功能描述:IC ADC 24BIT 2CH LN SD 24TSSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:16 采样率（每秒）:45k 数据接口:串行 转换器数目:2 功率耗散（最大）:315mW 电压电源:模拟和数字 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:28-SOIC（0.295"，7.50mm 宽） 供应商设备封装:28-SOIC W 包装:带卷 (TR) 输入数目和类型:2 个单端，单极 |
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