Performance sampled data system, low phase noise crystal oscillator to generate the sampling clock of the ADC (or DAC) hp Pavilion DV7 Accu sampling the Clock jitter modulation analog input / output signals, notebook batteries and increase noise and distortion bottom. The sampling clock generator should be isolated from digital circuitry with high noise, while grounded and decoupled to the analog ground layer and the of handling operational amplifier and ADC. , F analog input frequency, SNR perfect infinite resolution ADC's SNR, the only source of noise from the rms sampling clock jitter tj. Be seen by a simple example, Sony VGP-BPS2C/S Battery if tj = 50 ps (rms), f = 100 kHz, the SNR = 90 dB, equivalent to about 15-bit dynamic range.
Lower signal-to-noise ratio (SNR), mainly due to an external clock jitter result, measures must therefore be taken to make the sampling clock as noise-free as possible, only to have the lowest possible phase jitter. This requires that you must use the crystal oscillator. Several manufacturers offer small crystal oscillator, Toshiba PA3588U-1BRS Accu low jitter (<5 ps rms) can produce CMOS-compatible output. Ideally, the sampling clock of the crystal oscillator reference should separate grounding system of the analog ground layer. However, the the notebook battery system limit may lead to this point can not be achieved. Many cases, the higher frequency of the sampling clock must be generated from the digital ground layer.
the multipurpose system clock from the origin on the digital ground plane, and then must be transmitted to the analog ground layer on the ADC. Between the two layers of the ground noise is added directly to the clock signal, and generating excessive jitter. Reduce jitter may cause the signal-to-noise ratio, also interfere harmonic.isolate the sensitive analog parts and circuit boards. System star Acer AL10A31 Accu ground structure in connection with the position of the analog and digital ground layer mixed-signal devices.In different PCB (or even on the same PCB) having a number of the ADC or DAC system, the the notebook battery analog and digital ground layer connected in a plurality of points.