摘要:
A sigma-delta modulator for forming a digital output signal representative of a voltage level of an input signal, the sigma delta modulator having a node arranged to receive a current flow that is representative of the voltage level of the input signal and on whose voltage the digital output signal is dependent, the sigma-delta modulator comprising a plurality of capacitive elements for smoothing the current flow, each capacitive element being connected at one end to the node and at its other end to a respective switch unit and a plurality of switch units, each switch unit being arranged to connect the respective one of the capacitive elements to either a first voltage level or a second voltage level in dependence on the voltage at the node so as to provide feedback that affects the voltage at the node.
摘要:
The present invention provides a continuous-time delta-sigma modulator which is configured with an SC (SCR) feedback DA (103) for improving tolerance to jitter for a clock signal and operates stably by maintaining a certain feedback amount without being influenced by a change in a production process thereof or an operating temperature condition thereof. By adjusting a reference voltage Vref that determines an output voltage of the SC feedback DA (103), it is possible to feed back a certain amount of charge from the SC feedback DA (103) to a loop filter (101). Thereby, operation of the delta-sigma modulator is stabilized.
摘要:
An analogue-to-digital sigma-delta modulator for converting analogue input signals to digital output signals comprises a feedback path (1, 101, 201) for producing analogue feedback signals that are a function of the digital output signals (y, Y), an ' N '-stage (' N '≥2) integrator path (9 to 14, 109 to 114) for integrating analogue difference signals that are a difference function of the input signal and the analogue feedback signals, and a quantizer (3, 103) responsive to the signals integrated by the integrator means (9 to 14, 109 to 114) for producing the digital output signals (y, Y) at clock intervals. The feedback path includes 'N' feedback stages (15 to 17, 115 to 117) for respective integrator stages (9 to 14, 109 to 114). Each of the 'N' feedback stages (15 to 17, 115 to 117) comprises finite impulse response ('FIR') filters (15 to 19, 115 to 117), each of the FIR filters being of the same order 'M', where 'M' is at least two; at least the filter (15, 115) of the feedback stage that feeds back to the first integrator stage is a low pass filter. The integrator stages may be discrete-time integrators; the FIR filters reduce their sensitivity to feedback voltage step changes that would cause non-linearities due to slew-rate limitations. Alternatively, the integrator stages may be continuous-time integrators; the FIR filters reduce their sensitivity to clock pulse jitters. In the embodiment shown in Figure 11, the first integrator stage (109, 110) is a continuous-time integrator stage, and the remainder of the integrator stages (11 to 14) are discrete-time integrator stages.
摘要:
A method and apparatus for digital to analog conversion using sigma-delta modulation of the temporal spacing between digital samples. The method and apparatus of the present invention provides for sigma-delta modulation of the time base such that errors produced by nonuniform sampling are frequency-shaped to a region (i.e., shifted to higher frequencies) where they can be removed by conventional filtering techniques. In one embodiment, the digital data is interpolated by a fixed ratio and then decimated under control of a sigma-delta modulated frequency selection signal that represents, on average, the data rate of the incoming digital data stream. In another embodiment, the digital data is interpolated under control of a sigma-delta modulated frequency selection signal that represents, on average, the data rate of the incoming digital data stream and then decimated by a fixed ratio. The frequency signal selection number is modulated using an n-th order m-bit sigma-delta modulator. Data thus emerges from the interpolation/decimation process at the clock rate of the n-th order m-bit sigma-delta modulator. The method and apparatus converts the data rate of the incoming digital data stream to the data rate of the n-th order m-bit sigma-delta modulator.
摘要:
A method of Digital to Analogue conversion of an input signal Do for suppressing the effect of clock-jitter in a Delta-Sigma analogue to digital converter, or class D amplifier, comprises charging a capacitor (414) to a reference voltage value (Vref) during a first phase (φi) of a clock signal, discharging the capacitor during a second phase (φ2) of the clock signal, wherein the discharge is regulated by a biased transistor (418, 419), responsive to the voltage on the capacitor, in a first part of the second phase to provide an approximately constant discharge current, and regulated in a second part of the second phase for rapidly discharging the capacitance means before the end of the second phase; and providing an output (Ud, OUT) as a function of the discharge current and the input signal Do The output signal Ud, may be applied as a feedback signal to a loop filter in a Delta-Sigma converter Alternatively the output may represent the output of a Class D amplifier.
摘要:
Clock pulse generator apparatus comprising a clock pulse generator (CLK) for generating a train of primary clock pulses having leading and trailing edges. A delay line (14) produces a train of delayed clock pulses (CLK_D) presenting delayed edges whose timing relative to corresponding edges of the primary clock pulses (CLK) is defined by the delay line. A logic circuit (15) produces a train of combined clock pulses (CLK_JF) presenting leading and trailing edges defined alternately by one of the delayed edges and the corresponding edge of the primary clock pulse, so that the combined clock pulses comprise active clock phases (ACP) having widths defined by the delay line; the variability of the widths of the active clock phases (ACP) is smaller than the variability of the positions of the leading and trailing edges of the primary clock pulses (CLK). The active clock phases (ACP) alternate with non-active clock phases (NACP) whose widths vary as a function of variation in the positions of the primary clock pulses (CLK) and absord those variations. The delay line (14) comprises a series of cascaded, substantially identical delay elements (16). A temperature and process variation circuit (22) is also described. Application especially to continuous-time sigma-delta converters where a critical integrator (2; 10) integrates a signal over periods of time defined by the widths of the active clock phases (ACP).
摘要:
La présente invention concerne un convertisseur numérique-analogique en courant. Le convertisseur reçoit en entrée une succession de bits (y(k)) d'un signal binaire et délivre en sortie, échantillonné par un signal d'horloge (H), un courant positif (+l ref ) ou négatif (-I ref ) selon l'état du bit d'entrée. Il comporte au moins un circuit de contrôle du temps d'établissement du courant de sortie (+l ref , -I ref ) du convertisseur qui comporte une capacité (C 0 ) et un circuit de charge de cette capacité commandé par le signal d'horloge. Le temps d'établissement est contrôlé par la charge d'une capacité (C 0 ) sous un courant constant (+l 0 , -l 0 ) jusqu'à une tension de référence (+V 0 , -V 0 ). Le circuit de contrôle du temps d'établissement du courant de sortie peut comporter deux tensions de référence, la capacité étant chargée puis déchargée entre ces deux tensions. Le temps d'établissement du courant de sortie est alors la somme du temps mis pour charger la capacité et du temps mis pour décharger la capacité. On peut envoyer directement le courant de charge et décharge de la capacité dans la charge de sortie (R b , C b ) du convertisseur, au moyen de commutateurs (T1, T2, T3, T4) et de miroirs de courant (Q7, Q8, Q9, Q10). On utilise alors deux capacités (C 0 , C' 0 ) que l'on charge et décharge. Pendant que l'une des capacités se charge, l'autre se décharge. L'invention s'applique notamment pour des convertisseurs numérique-analogique du type sigma-delta.