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UWT1E151MNR1GS_Datasheet PDF

来源:LM317 Electronics Components编辑:Murrplastik时间:2021-06-15 15:22:58

Because cone-based equivalence checkers require the models to be represented as combinational logic, the behavioral models must be translated to a functionally equivalent state-based representation, such as RTL. This can be a difficult task, error prone at least, that imposes unnecessary restrictions on logic designers and decreases productivity. Symbolic simulation directly handles behavioral code, eliminating these restrictions.

Not only does a shielded motor power cable contain” capacitively coupled cable noise, it will provide the low-impedance return path for the motor’s own noise current. Consequently, and in violation of conventional wisdom for avoiding ground loops, the cable shield is connected to both servo amplifier power supply ground, Figure 1 , and to the motor frame as well.

UWT1E151MNR1GS_Datasheet PDF

The shield should envelop (cage) as much of the power cable as possible, and its connections to amplifier and motor should be kept short. Avoid connecting with tight-radius bends that add impedance, which can be significant at noise frequencies, to the current path.

For motors with integral encoder and Hall sensors, harmful coil-to-sensor noise coupling can occur. Capacitance between motor coils and encoder circuits is the danger. Although the degree of noise coupling for a given motor can’t be altered, it pays to select a servo motor that keeps internal signal cables well segregated from power circuits. Pay special attention to the way power and signal wires are shielded and separated as they pass through motor-frame bushing to its connection box.

Worst-Case Noise Condition Noise currents coupled into the cable shield and motor frame reach a maximum when the leading and trailing edges of all three U, V and W drive waveforms coincide. (Leading edges of the waveforms are in phase, anyway). This waveform coincidence occurs at zero load, Figure 1, when the motor is stationary. Trailing edges also approach when the motor is holding” and draws only a light load.

UWT1E151MNR1GS_Datasheet PDF

The calculations of Figure 1 determine worst-case noise for ten feet of shielded power cable. Motor PWM drive pulses have approximately 0.5V/ns rise rate. Cable-to-shield capacitance is measured at 2.5 nF. Motor coil-to-frame capacitance is about 0.5 nF. From Inoise = C dv/dt, cable current amounts to about 1.5 A peak. A noise current of this magnitude can certainly cause significant misinterpretation of a sensitive logic circuit’s ONE and ZERO values.

In contrast to Figure 1’s systematic noise reduction, Figure 2 highlights the interference-prone before.”

UWT1E151MNR1GS_Datasheet PDF

This poorly designed system lacks a safe return for path both motor and cable noise currents. For illustration’s sake, there’s also an acoustic sensor whose signal cables run in the same bundle as motor power cables. Coupling between power cable and acoustic-signal cable adds noise that undermines acoustic data integrity. Besides compromising the acoustic processor’s circuits, the interfering noise current must also complete its own return path (from acoustic processor), to the servo amplifier’s power semiconductors. In doing so, the current may well return via the machine frame, creating disturbances elsewhere in the system.

Processor and memory block The processor and memory block is the next major power consumer in the system. In a digital system, higher operating frequency implies higher switching loss and hence larger power consumption. For example, E = 0.5CV2 F, where E refers to switching power loss, C to the effective capacitance, V to the voltage, and F to the frequency.

Clock scaling refers to setting the system's clock frequency to the minimum possible value without compromising performance. This would require dynamic changes in the core, memory, and peripheral frequencies. The system must be intelligent enough to change the clock settings depending on the codec chosen by the user. Selecting the optimal clock frequencies could save around 5% of the total power.

The type of SDRAM chosen plays a key role in the power chart. Mobile SDRAMs are better suited for battery-based systems as they consume about 60% less power compared to conventional SDRAMs. SDRAM controllers allow designers to set the required drive strength. Hence, this should be set to the minimum while configuring the controller. SDRAM refresh period should be kept constant by reprogramming the refresh counter after each clock change.

Modern Multimedia processors typically come with multiple peripherals like UART, USB, I2 C, Video Encoder, and so on. The designer must take care to switch off the peripherals that aren't in use. Switching off the clocks to the respective modules can accomplish this, saving about 5% of the total power.

Some processors allow a range of supply voltages to be applied to their cores. For example, the data sheet would say core voltage could be between 1.2 and 1.3 V. It's always advisable to stick to the lowest possible voltage specified. This reduces the switching losses and hence, reduce the total power consumed by the core without hampering its performance.

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