The process of charging the sampling capacitance causes a voltage drop (or peak) across external input capacitor CIN. The subsequent process of charging the sampling capacitor is much slower due to this higher input impedance. The acquisition time must be properly set while considering the time constant of the sampling capacitor charging.
During the acquisition time (TAQ), the sampling capacitor (CSH) must be charged to an acceptable minimal portion of the voltage level of the measured input voltage. In general, the deviation from the measured input voltage at the end of acquisition time must not exceed 0.5 LSB of the full scale range.
The value of initial voltage across the sampling capacitor CSH depends on the specific ADC input architecture. In a case of redistribution charging architecture of SAR ADC or if a presampling circuit is used, then the initial voltage can be equal to VREFL or VREFH.
The full scale range is equal to 3.3V that is, VFSR = 3.3V. The maximum capacitance of sampling capacitor is 10pF (see CADIN in ). The sampling capacitance defined in datasheet as input capacitance CADIN represents total capacitance of the bank of capacitances implemented in SAR ADCs with redistribution charging.
The voltage across sampling capacitance is defined as: Where VCIN0 represents the initial voltage across input capacitance (this voltage is equal to the measured input voltage), VCSH0 represents initial voltage across input capacitance CIN.
Switched-capacitor circuits have four sources of noise: noise of the sampling phase, noise of the holding phase, the op-amps noise and the quantisation noise. The last source of the noise, quantisation, has been mentioned in Section 3.
Current sampling method and circuit
The invention also provides a current sampling circuit, comprising a current sampling transistor, a capacitor, an amplifier, and a switch arrangement. The capacitor arrangement is...
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A High-Accuracy Capacitor Condition Monitoring Scheme at Low …
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Methodology for designing and verifying switched‐capacitor sample …
This study presents a full methodological approach to designing and verifying differential sample and hold switched-capacitor circuits generally used in analogue-to-digital converters (ADCs). It provides a step-by-step process for translating system requirements such as signal-to-noise ratio and sampling frequency into ADC requirements and ...
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AN-742 APPLICATION NOTE
The ADC''s sample-and-hold amplifier circuit (SHA) is mainly comprised of an input switch, an input sampling capacitor, a sampling switch, and an amplifier. As Figure 1 shows, the input switch interfaces the driver circuit with the input capacitor. When the input switch is on (track mode), the driver circuit drives the input capacitor. The ...
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Texas Instruments
current sensing applications – allowing them specifically to address their unique design challenges. This e-book was created to further simplify the current sensing design process by helping you quickly and efficiently narrow down the list of potential devices that align best with your particular system''s requirements. The current sensing information featured in this e-book …
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Capacitor current loop design for dynamic characteristics …
The CL-type filters adopted in grid-connected current source inverters (CSIs) causes resonance. Capacitor voltage feedback (CVF) based active damping (AD) can suppress this resonance, and has the advantage of simple implementation. However, the amplitude of the filter capacitor voltage is much larger than the amplitude of the direct current, which leads to …
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Using ADC to measure a current source with no external components
Ground the ADC''s sampling capacitor and the input pin to discharge its parasitic capacitance. Disconnect ground from the ADC input pin so that the current source can now charge the sampling capacitor. Wait for some fixed amount of time (discussed in section 6. Determining the integration period) to allow the current to charge the capacitor.
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with capacitor-current feedback controlled LCL-type grid …
capacitor-current sampling instant towards the reference update time of PWM to reduce the digital time delay. Nevertheless, aliasing might occur if the capacitor-current sampling time is not properly located. Moreover, in addition to the method of time delay compensation that is adopted to ensure the stability of the digitally controlled LCL-type grid-connected inverter with capacitor …
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Inputs Currents for High-Resolution ADCs
This application report explains how the input sampling works and how input impedance can be calculated in the ADS1216, ADS1217, and ADS1218 family of ADCs. This family of ADCs are of the delta-sigma (∆Σ) variety that use oversampling as a means of achieving high resolution.
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Cookbook for SAR ADC Freescale Semiconductor Measurements
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How to choose the sampling capacitor for touch sensing …
Introduction Capacitors feature some non-ideal characteristics that unfortunately limit their use in some applications. The objective of this document is to help designers in selecting the right sampling capacitor (C S) for their touch sensing applications by investigating the most important undesirable characteristics.
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A High-Accuracy Capacitor Condition Monitoring Scheme at Low Sample …
The core technology of the scheme is a current integral reconstruction method based on linear fitting which improves monitoring accuracy at low sampling rates. The article begins by introducing the ac/dc converter system targeted by this scheme. It then proposes an improved current reconstruction method and a suitable equivalent capacitance ...
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Cookbook for SAR ADC Freescale Semiconductor Measurements
This interval represents the charging of sampling capacitor CSH by energy accumulated in the input capacitor (usually VCIN0 = VIN). In a steady state, no energy is transferring; the current is zero, and voltages across both capacitors are equal. A mathematical expression of steady state voltage is defined using substitution t→∞ intoEqn.1 and 2:
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High Speed ADC Sampling Transients | Analog Devices
As such, they include sampling capacitors and sampling switches. The action of these elements as they alternately track the input signal and hold its voltage produces small transient voltages and currents. These transients can introduce distortion into the circuitry that drives the ADC analog input.
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AN-742 APPLICATION NOTE
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Methodology for designing and verifying switched …
It also provides practical methods for verifying the stability of the system by using step voltage and step current techniques. A design and simulation example for a differential sample and...
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Introduction to Switched-Capacitor Circuits
Introduction to Switched-Capacitor Circuits 400 12.2 Sampling Switches 12.2.1 MOSFETS as Switches A simple sampling circuit consists of a switch and a capacitor [Fig. 12.8(a)]. A MOS transistor can serve as a switch [Fig. 12.8(b)] because (a) it can be on while carrying zero current, and (b) its C Vin Vout C Vin Vout CK (a) (b) HH M1 Figure 12.8. (a) Simple sampling circuit, …
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Capacitor-Current-Feedback Active Damping With Reduced …
To address this issue, this paper proposes a capacitor-current-feedback active damping with reduced computation delay, which is achieved by shifting the capacitor current sampling instant towards the PWM reference update instant. With this method, the virtual impedance exhibits more like a resistor in a wider frequency range, and the open-loop ...
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Methodology for designing and verifying switched-capacitor sample …
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Methodology for designing and verifying …
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SWITCHED-CAPACITOR ADC ANALOG INPUT CALCULATIONS
Switched-Capacitor ADC Analog Input Calculations 3 1 LSB 1/16 LSB VC 1 LSB VS 4567 8 0V VC(1/16 LSB) VFS tC(1/16 LSB) tc – Charge Time – TC Vc – Internal Capacitor Voltage – V Figure 2. Internal Capacitor Voltage, Vc, as a Function of the Charge Time, tc The final capacitor voltage to achieve 1/16 LSB is given by: Vc 1 16 Vs– Vs 2N 4 ...
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Inputs Currents for High-Resolution ADCs
This application report explains how the input sampling works and how input impedance can be calculated in the ADS1216, ADS1217, and ADS1218 family of ADCs. This family of ADCs are …
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A 16-bit current sample/hold circuit using a digital CMOS process
If the input is held constant over several cycles, clock feedthrough errors can be significantly reduced, but for a dynamic input, the ultimate solution has been to use a large sampling capacitor and small-switches. We propose a method of building a highly accurate oversampling current-mode sample/hold circuit using feedback architectures ...
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Methodology for designing and verifying switched‐capacitor …
If the input is held constant over several cycles, clock feedthrough errors can be significantly reduced, but for a dynamic input, the ultimate solution has been to use a large sampling …
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Methodology for designing and verifying switched‐capacitor sample …
It provides a step-by-step process for translating system requirements such as signal-to-noise ratio and sampling frequency into ADC requirements and subsequently into operational amplifier topology and specifications. It also includes the design process of a switched-capacitor common mode feedback circuit to control the common mode output voltage.
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Improved Deadbeat Predictive Current Control for CSI-Fed High …
3 · This article studies the deadbeat predictive current control for current-source-inverter-fed high-speed permanent magnet synchronous machine drive. Since the AC filter capacitors increase the order of the control system, the traditional 2-step-reaching DPCC will lead to motor current oscillations due to the excessive current change rate. To deal with this problem, a …
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