PCM1608YSLASH2K datasheet(29/46 Pages) TI1

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ANALOG OUTPUTS

f − Frequency − Hz

−100

−80

−60

−40

−20

100

10M

G019

10k

100k

VCOM OUTPUT

–

VCOM

OPA337

µF

PCM1608

S0054-03

BIAS +

PCM1608

SBAS164B – DECEMBER 2000 – REVISED JULY 2005

The PCM1608 includes eight independent output channels, VOUT1 through VOUT8. These are unbalanced

outputs, each capable of driving 3.1 Vp-p typical into a 5-k

Ω ac load with V

CC = 5 V. The internal output

amplifiers for VOUT1 through VOUT8 are dc-biased to the common-mode (or bipolar zero) voltage, equal to VCC/2.

The output amplifiers include an RC continuous-time filter, which helps to reduce the out-of-band noise energy

present at the DAC outputs due to the noise-shaping characteristics of the PCM1608 delta-sigma DACs. The

frequency response of this filter is shown in Figure 28. By itself, this filter is not enough to attenuate the

out-of-band noise to an acceptable level for most applications. An external low-pass filter is required to provide

sufficient out-of-band noise rejection. Further discussion of DAC post-filter circuits is provided in the Application

Information section of this data sheet.

Figure 28. Output-Filter Frequency Response

One unbuffered, common-mode voltage output pin, VCOM (pin 15), is brought out for decoupling purposes. This

pin is nominally biased to a dc voltage level equal to VCC/2. If this pin is to be used to bias external circuitry, a

voltage follower is required for buffering purposes. Figure 29 shows an example of using the VCOM pin for

external biasing applications.

Figure 29. Biasing External Circuits Using the VCOM Pin

PCM1608Y/2K Datasheet(PDF) 29 Page - Texas Instruments