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TC7116A データシート(PDF) 8 Page - Microchip Technology |
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TC7116A データシート(HTML) 8 Page - Microchip Technology |
8 / 26 page TC7116/A/TC7117/A DS21457D-page 8 2002-2012 Microchip Technology Inc. 3.0 DETAILED DESCRIPTION (All Pin Designations Refer to 40-Pin PDIP.) 3.1 Analog Section Figure 3-1 shows the block diagram of the analog sec- tion for the TC7116/TC7116A and TC7117/TC7117A. Each measurement cycle is divided into three phases: (1) Auto-Zero (AZ), (2) Signal Integrate (INT), and (3) Reference Integrate (REF), or De-integrate (DE). 3.1.1 AUTO-ZERO PHASE High and low inputs are disconnected from the pins and internally shorted to analog common. The reference capacitor is charged to the reference voltage. A feed- back loop is closed around the system to charge the auto-zero capacitor (CAZ) to compensate for offset volt- ages in the buffer amplifier, integrator, and comparator. Since the comparator is included in the loop, AZ accuracy is limited only by system noise. The offset referred to the input is less than 10 V. 3.1.2 SIGNAL INTEGRATE PHASE The auto-zero loop is opened, the internal short is removed, and the internal high and low inputs are connected to the external pins. The converter then inte- grates the differential voltages between VIN+ and VIN- for a fixed time. This differential voltage can be within a wide Common mode range: 1V of either supply. How- ever, if the input signal has no return with respect to the converter power supply, VIN- 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 determined. FIGURE 3-1: Analog Section of TC7116/TC7116A and TC7117/TC7117A 3.1.3 REFERENCE INTEGRATE PHASE The final phase is reference integrate, or de-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 integrator output to return to zero. The time required for the output to return to zero is proportional to the input signal. The digital reading displayed is: EQUATION 3-1: 3.1.4 REFERENCE The positive reference voltage (VREF+) is referred to analog common. TC7116 TC7116A TC7117 TC7117A CREF CREF+ CREF- RINT V+ CAZ Auto-Zero VINT 28 35 29 27 33 36 34 10 μA 31 AZ AZ INT AZ & DE (±) 32 30 INT 26 Integrator V+ -3V Comparator To Digital Section DE (+) DE (–) DE (+) DE (–) V+ AZ Analog Common VIN+ VIN- VBUFF CINT VREF+ Low Temp. Drift Zener VREF V- + – + – + + – 1000 = VIN VREF |
同様の部品番号 - TC7116A |
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同様の説明 - TC7116A |
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