Datasheet

PRODUCT OVERVIEW
ANALOG OUTPUTS
VOLTAGE REFERENCE VCOM
PCM1789
SBAS451A – OCTOBER 2008 – REVISED JANUARY 2009 .............................................................................................................................................. www.ti.com
The PCM1789 is a high-performance stereo DAC targeted for consumer audio applications such as Blu-ray Disc
players and DVD players, as well as home multi-channel audio applications (such as home theater and A/V
receivers). The PCM1789 consists of a two-channel DAC. The DAC output type is fixed with a differential
configuration. The PCM1789 supports 16-/20-/24-/32-bit linear PCM input data in I
2
S and left-justified audio
formats, and 24-bit linear PCM input data in right-justified and DSP formats with various sampling frequencies
from 8 kHz to 192 kHz. The PCM1789 offers three modes for device control: two-wire I
2
C software, three-wire
SPI software, and hardware.
The PCM1789 includes a two-channel DAC, with a pair of differential voltage outputs pins. The full-scale output
voltage is (1.6 × VCC1) V
PP
in differential output mode. A dc-coupled load is allowed in addition to an ac-coupled
load, if the load resistance conforms to the specification. These balanced outputs are each capable of driving 0.8
VCC1 (4 V
PP
) typical into a 5-k Ω ac-coupled or 15-k Ω dc-coupled load with VCC1 = +5 V. The internal output
amplifiers for VOUTL and VOUTR are biased to the dc common voltage, equal to 0.5 VCC1.
The output amplifiers include an RC continuous-time filter that helps to reduce the out-of-band noise energy
present at the DAC outputs as a result of the noise shaping characteristics of the PCM1789 delta-sigma ( Δ Σ )
DACs. The frequency response of this filter is shown in the Analog Filter Characteristic (Figure 10 ) of the Typical
Characteristics . 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.
The PCM1789 includes a pin for the common-mode voltage output, VCOM. This pin should be connected to the
analog ground via a decoupling capacitor. This pin can also be used to bias external high-impedance circuits, if
they are required.
12 Submit Documentation Feedback Copyright © 2008 – 2009, Texas Instruments Incorporated
Product Folder Link(s): PCM1789