 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
AD7707 Datasheet(PDF) 47 Page - Analog Devices |
|
|
|||||||||||||||||||||||||||||
AD7707 Datasheet(HTML) 47 Page - Analog Devices |
|
|
47 / 53 page  AD7707 Rev. B | Page 46 of 52 CHART RECORDERS Another area where both high and low level input channels are usually found is in chart recorder applications. Circular chart recorders generally have two requirements. The first utilizes the low level input channels of the AD7707 to measure inputs from thermocouples, RTDs, and pressure sensors. The second requirement is to be able to measure dc input voltage ranges up to ±10 V. The high level input channel is ideally suited to this measurement because there is no external signal conditioning required to accommodate these high level input signals. ACCOMMODATING VARIOUS HIGH LEVEL INPUT RANGES The high level input channel, AIN3 can accommodate input signals from −11 V to +30 V on its input. This is achieved using on-chip thin film resistors that map the signal on AIN3 into a usable range for the AD7707. The input structure is arranged so that the Σ-Δ converter sees the same impedance at its AIN(+) and AIN(−) inputs. The signal on the AIN3 input is referenced to the HICOM input and the VBIAS signal is used to adjust the common-mode voltage at the modulator input. In normal 5 V operation, VBIAS is normally connected to 2.5 V and HICOM is connected to AGND. This arrangement ensures that the voltages seen at the modulator input are within the common- mode range of the buffer. The differential voltage, AIN, seen by the AD7707 when using the high level input channel is the difference between AIN3(+) and AIN3(−), as shown in Figure 31, and must remain within the absolute common-mode range of the modulator. AIN3(+) = (AIN3 + 6 × VBIAS+ VHICOM)/8 AIN3(−) = 0.75 × VBIAS + 0.25 VHICOM AIN = (AIN3 − VHICOM)/8 AIN 5kΩ 30kΩ 15kΩ 5kΩ AIN3 VBIAS HICOM AIN3(+) AIN3(–) 30kΩ MUX Figure 31. AIN3, High Level Input Channel Structure The VBIAS and HICOM inputs are used to tailor the input range on the high level input channel to suit a variety of input ranges. Table 28 applies for operation with AVDD = 5 V, and REF(+) − REF(−) = 2.5 V. Table 29 applies for operation with AVDD = 3 V, and REF(+) − REF(−) = 1.25 V. TYPICAL INPUT CURRENTS When using the high level input channel, power dissipation is determined by the currents flowing in the AIN3, VBIAS, and HICOM inputs. The voltage level applied to these inputs determines whether the external source driving these inputs needs to sink or source current. Table 30 shows the currents associated with the ±10 V input range. These inputs should be driven from a low impedance source in all applications to prevent significant gain errors being introduced. Table 28. Configuration of AD7707 vs. Input Range on AIN3 (AVDD = 5 V, VREF = 2.5 V) AIN3 Range VBIAS HICOM Gain Buffered/Unbuffered AIN Range ±10 V 2.5 V AGND 2 Buffered/Unbuffered 1.875 V ± 1.25 V ±5 V 2.5 V AGND 4 Buffered/Unbuffered 1.875 V ± 0.625 V 0 V to 10 V 2.5 V AGND 2 Buffered/Unbuffered 1.875 V to 3.125 V 0 V to 20 V AGND AGND 1 Buffered 0 V to 2.5 V 2.5 V AGND 1 Buffered 1.875 V to 4.375 V −5 V to +10 V 2.5 V 2.5 V 2 Buffered/Unbuffered 2.5 V ± 0.9375 V Table 29. Configuration of AD7707 vs. Input Range on AIN3 (AVDD = 3 V, VREF = 1.25 V) AIN3 Range VBIAS HICOM Gain BUF/UNBUF AIN Range ±5 V 1.25 V AGND 2 Unbuffered 0.9375 V ± 0.625 V 0 V to 10 V 1.25 V AGND 1 Unbuffered 0.9375 V to 2.1875 V −5 V to +10 V 1.25 V 2.5 V 1 Unbuffered 1.5625 V ± 0.9375 V −7.5 V to +10 V 1.25 V 0 V 1 Unbuffered 0 V to 2.1875 V ±10 V 1.666 V AGND 1 Unbuffered 1.25 V ± 1.25 V Table 30. Typical Input Current vs. Voltage on AIN3 AIN3 VBIAS HICOM I (AIN3) I (VBIAS) I (HICOM) −10 V 2.5 V AGND −354 μA 500 μA −146 μA 0 V 2.5 V AGND −62 μA 250 μA −188 μA +10 V 2.5 V AGND 229 μA 0 μA −229 μA |
Similar Part No. - AD7707_17 |
|
Similar Description - AD7707_17 |
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List 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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
