The PCM1681 and PCM1681-Q1 are CMOS monolithic integrated circuits which feature an eight-channel 24-bit audio digital-to-analog converter (DAC) and support circuitry in small 28-lead TSSOP PowerPAD packages

PCM1681

Manufacturer Part NumberPCM1681
DescriptionThe PCM1681 and PCM1681-Q1 are CMOS monolithic integrated circuits which feature an eight-channel 24-bit audio digital-to-analog converter (DAC) and support circuitry in small 28-lead TSSOP PowerPAD packages
ManufacturerTexas Instruments
PCM1681 datasheet
 


Specifications of PCM1681

# Dacs8# Inputs / # Outputs0 / 8
ArchitectureCurrent Segment DACResolution(bits)24
Sampling Rate(max)(khz)200Control InterfaceSPI, I2C,H/W
Digital Audio InterfaceL,R,I2S,TDM,DSPThd+n(typ)(%)0.002
Dac Snr(typ)(db)105Power Consumption(typ)(mw)386
Operating Temperature Range(c)-40 to 85Analog Voltage Av/dd(min)(v)4.5
Analog Voltage Av/dd(max)(v)5.5Pin/package28HTSSOP
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PCM1681
PCM1681-Q1
SLES211B – FEBRUARY 2008 – REVISED JUNE
2008....................................................................................................................................................
POWER-SUPPLY AND GROUNDING
The PCM1681 and PCM1681-Q1 require 5 V for the analog supply and 3.3 V for the digital supply. The 5-V
supply is used to power the DAC analog and output filter circuitry, and the 3.3 V supply is used to power the
digital filter and serial interface circuitry. For best performance, a 5-V supply and a 3.3-V supply with linear
regulators are recommended.
Five capacitors are required for supply bypassing, as shown in
close as possible to the PCM1681 and PCM1681-Q1 package. The 10- F capacitor should be tantalum or
aluminum electrolytic, while the three 1- F capacitors are ceramic.
D/A OUTPUT FILTER CIRCUITS
ΔΣ DACs use noise shaping techniques to improve in-band signal-to-noise ratio (SNR) performance at the
expense of generating increased out-of-band noise above the Nyquist frequency, or f
must be low-pass filtered in order to provide optimal converter performance. This is accomplished by a
combination of on-chip and external low-pass filtering.
Figure 32
and
Figure 34
show the recommended external low-pass active filter circuits for dual- and
single-supply applications. These circuits are second-order Butterworth filters using a multiple-feedback (MFB)
circuit arrangement, which reduces sensitivity to passive component variations over frequency and temperature.
For more information regarding MFB active filter design, see Dynamic Performance Testing of Digital Audio D/A
Converters (SBAA055).
Because the overall system performance is defined by the quality of the D/A converters and their associated
analog output circuitry, high-quality audio operational amplifiers are recommended for the active filters. Texas
Instruments’ OPA2353 and OPA2134 dual operational amplifiers are shown in
recommended for use with the PCM1681 and PCM1681-Q1.
R
1
+
V
IN
C
3
10 F
R
2
A
+ *
V
R
1
PCB LAYOUT GUIDELINES
A typical printed circuit board (PCB) floor plan for the PCM1681 and PCM1681-Q1 is shown in
ground plane is recommended, with the analog and digital sections being isolated from one another using a split
or cut in the circuit board. The PCM1681 and PCM1681-Q1 should be oriented with the digital I/O pins facing the
ground plane split/cut to allow for short, direct connections to the digital audio interface and control signals
originating from the digital section of the board.
Separate power supplies are recommended for the digital and analog sections of the board. This prevents the
switching noise present on the digital supply from contaminating the analog power supply and degrading the
dynamic performance of the PCM1681 and PCM1681-Q1.
The PowerPAD can be left open without being soldered to the ground plane of the PCB for the PCM1681.
However, it must be soldered to the ground plane which has low thermal resistance for the PCM1681-Q1.
34
Submit Documentation Feedback
Figure
33. These capacitors should be located as
R
C
2
1
R
3
2
R
4
1
OPA2134
3
47
C
+
2
Figure 34. Dual-Supply Filter Circuit
Product Folder Link(s):
PCM1681 PCM1681-Q1
www.ti.com
/2. The out-of-band noise
S
Figure 32
and
Figure
34, and are
Example:
R
: 5.1 k
1
R
: 8.2 k
2
R
: 560
3
C
: 470 pF
1
V
OUT
C
: 4700 pF
2
A
: −1.61
V
f
: 57 kHz
c
Figure
35. A
Copyright © 2008, Texas Instruments Incorporated