PCM1795 Datasheet, PDF (38/63 Pages) Texas Instruments – 32-Bit, 192-kHz Sampling, Advanced Segment, Stereo Audio Digital-to-Analog Converter

PCM1795
SLES248A – MAY 2009 – REVISED MARCH 2015
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Typical Applications (continued)
8.2.1.2 Detailed Design Procedure
The design of the application circuit is very important in order to actually realize the high S/N ratio of which the
PCM1795 device is capable, because noise and distortion that are generated in an application circuit are not
negligible.
In the third-order, low-pass filter (LPF) circuit of Figure 53, the output level of 2.1 V RMS and 123-dB signal-to-
noise ratio is achieved.
Figure 54 shows a circuit for the DSD mode, which is a fourth-order LPF in order to reduce the out-of-band
noise.
8.2.1.2.1 I/V Section
The current of the PCM1795 device on each of the output pins (I_OUTL+, I_OUTL–, I_OUTR+, I_OUTR–) is 4 mA_PP at 0
dB (full-scale). The voltage output level of the current-to-voltage (I/V) converter, V_I, is given by Equation 2.
V_I = 4 mA_PP × R_F
where
• R_F = feedback resistance of the I/V converter
(2)
An NE5534 operational amplifier is recommended for the I/V circuit to obtain the specified performance. Dynamic
performance such as the gain bandwidth, settling time, and slew rate of the operational amplifier affects the
audio dynamic performance of the I/V section.
8.2.1.2.2 Differential Section
The PCM1795 device voltage outputs are followed by differential amplifier stages that sum the differential signals
for each channel, creating a single-ended I/V op-amp output. In addition, the differential amplifiers provide a low-
pass filter function.
The operational amplifier recommended for the differential circuit is the low-noise type.
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