công cụ tìm kiếm bảng dữ liệu linh kiện điện tử |
|
ADS7819 bảng dữ liệu(PDF) 10 Page - Texas Instruments |
|
ADS7819 bảng dữ liệu(HTML) 10 Page - Texas Instruments |
10 / 13 page 10 ® ADS7819 CALIBRATION The ADS7819 can be trimmed in hardware or software. The offset should be trimmed before the gain since the offset directly affects the gain. Hardware Calibration To calibrate the offset and gain of the ADS7819, install the proper resistors and potentiometers as shown in Figure 4a. The calibration range is ±12mV for bipolar zero and ±30mV for full scale. Potentiometer P1 and resistor R1 form the offset adjust circuit and P2 and R2 the gain adjust circuit. The exact values are not critical. R1 and R2 should not be made any larger than the value shown. They can easily be made smaller to provide increased adjustment range. Reducing these below 15% of the indicated values could begin to adversely affect the operation of the converter. P1 and P2 can also be made larger to reduce power dissipa- tion. However, larger resistances will push the useful adjust- ment range to the edges of the potentiometer. P1 should probably not exceed 20k Ω and P2 100kΩ in order to main- tain reasonable sensitivity. Software Calibration To calibrate the offset and gain of the ADS7819, no external resistors are required. See the No Calibration section for details on the effects of the external resistor. No Calibration See Figure 4b for circuit connections. Note that the actual voltage dropped across the 50 Ω resistor is nearly two orders of magnitude lower than the voltage dropped across the internal resistor divider network. This should be taken into consideration when choosing the accuracy and drift specifi- cations of the external resistors. In most applications, 1% metal-film resistors will be sufficient. The external 50 Ω resistor shown in Figure 4b may not be necessary in some applications. This resistor provides trim capability for the offset and compensates for a slight gain adjustment internal to the ADS7819. Not using the 50 Ω resistor will cause a small gain error but will have no effect on the inherent offset error. Figure 5 shows typical transfer function characteristics with and without the 50 Ω resistor in the circuit. REFERENCE The ADS7819 can operate with its internal 2.5V reference or an external reference. By applying an external reference to pin 3, the internal reference can be bypassed. The reference voltage at REF is buffered internally and output on CAP (pin 4). The internal reference has a 6 ppm/ °C drift (typical) and accounts for approximately 20% of the full scale error (FSE = ±0.5% for low grade, ±0.25% for high grade.) REF REF (pin 3) is an input for an external reference or the output for the internal 2.5V reference. A 0.1 µF capacitor should be connected as close to the REF pin as possible. The capacitor and the output resistance of REF create a low pass filter to band limit noise on the reference. Using a smaller value capacitor will introduce more noise to the reference degrading the SNR and SINAD. The REF pin should not be used to drive external AC or DC loads. The range for the external reference is 2.3V to 2.7V and determines the actual LSB size. Increasing the reference voltage will increase the full scale range and the LSB size of the converter which can improve the SNR. FIGURE 5. Circuit Diagram With and Without External Resistors. –2.46V –2.5V Digital Output + Full Scale Analog Input – Full Scale Typical Transfer Function with 50 Ω Resistor Typical Transfer Function Without 50 Ω Resistor 2.46V 2.5V |
Số phần tương tự - ADS7819 |
|
Mô tả tương tự - ADS7819 |
|
|
Link URL |
Chính sách bảo mật |
ALLDATASHEET.VN |
Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không? [ DONATE ] |
Alldatasheet là | Quảng cáo | Liên lạc với chúng tôi | Chính sách bảo mật | Trao đổi link | Tìm kiếm theo nhà sản xuất All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |