Electronic Components Datasheet Search |
|
ICL7135 Datasheet(PDF) 5 Page - Intersil Corporation |
|
ICL7135 Datasheet(HTML) 5 Page - Intersil Corporation |
5 / 15 page 5 FN3093.4 Detailed Description Analog Section Figure 3 shows the Block Diagram of the Analog Section for the ICL7135. Each measurement cycle is divided into four phases. They are (1) auto-zero (AZ), (2) signal-integrate (INT), (3) de-integrate (DE) and (4) zero-integrator (Zl). Auto-Zero Phase During auto-zero, three things happen. First, input high and low are disconnected from the pins and internally shorted to analog COMMON. Second, the reference capacitor is charged to the reference voltage. Third, a feedback loop is closed around the system to charge the auto-zero capacitor CAZ to compensate for offset voltages in the buffer amplifier, integrator, and comparator. Since the comparator is included in the loop, the AZ accuracy is limited only by the noise of the system. In any case, the offset referred to the input is less than 10 μV. Signal Integrate Phase During signal integrate, the auto-zero loop is opened, the internal short is removed, and the internal input high and low are connected to the external pins. The converter then integrates the differential voltage between IN HI and IN LO for a fixed time. This differential voltage can be within a wide common mode range; within one volt of either supply. If, on the other hand, the input signal has no return with respect to the converter power supply, IN LO can be tied to analog COMMON to establish the correct common-mode voltage. At the end of this phase, the polarity of the integrated signal is latched into the polarity F/F. De-Integrate Phase The third phase is de-integrate or reference integrate. Input low is internally connected to analog COMMON and input high is connected across the previously charged reference capacitor. Circuitry within the chip ensures that the capacitor will be connected with the correct polarity to cause the inte- grator output to return to zero. The time required for the out- put to return to zero is proportional to the input signal. Specifically the digital reading displayed is: . Zero Integrator Phase The final phase is zero integrator. First, input low is shorted to analog COMMON. Second, a feedback loop is closed around the system to input high to cause the integrator output to return to zero. Under normal condition, this phase lasts from 100 to 200 clock pulses, but after an overrange conversion, it is extended to 6200 clock pulses. Differential Input The input can accept differential voltages anywhere within the common mode range of the input amplifier; or specifically from 0.5V below the positive supply to 1V above the negative supply. In this range the system has a CMRR of 86dB typical. However, since the integrator also swings with the common mode voltage, care must be exercised to assure the integrator output does not saturate. A worst case condition would be a large positive common-mode voltage with a near full scale negative differential input voltage. The negative input signal drives the integrator positive when most of its swing has been used up by the positive common mode voltage. For these critical applications the integrator swing can be reduced to less than the recommended 4V full scale swing with some loss of accuracy. The integrator output can swing within 0.3V of either supply without loss of linearity. Analog COMMON Analog COMMON is used as the input low return during auto- zero and de-integrate. If IN LO is different from analog COMMON, a common mode voltage exists in the system and is taken care of by the excellent CMRR of the converter. However, in most applications IN LO will be set at a fixed known voltage (power supply common for instance). In this application, analog COMMON should be tied to the same point, thus removing the common mode voltage from the converter. The reference voltage is referenced to analog COMMON. Reference The reference input must be generated as a positive voltage with respect to COMMON, as shown in Figure 4. OUTPUT COUNT 10,000 VIN VREF --------------- ⎝⎠ ⎜⎟ ⎛⎞ = FIGURE 4A. FIGURE 4B. FIGURE 4. USING AN EXTERNAL REFERENCE IZ 6.8V V- ZENER REF HI ICL7135 COMMON V+ 6.8k Ω ICL8069 REF HI ICL7135 COMMON V+ V+ 20k Ω 1.2V REFERENCE ICL7135 |
Similar Part No. - ICL7135_07 |
|
Similar Description - ICL7135_07 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |