24-Bit, 96kHz

BiCMOS Sign-Magnitude

DIGITAL-TO-ANALOG CONVERTER

49%

FPO

International Airport Industrial Park · Mailing Address: PO Box 11400, Tucson, AZ 85734 · Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 · Tel: (520) 746-1111 · Twx: 910-952-1111

Internet: http://www.burr-brown.com/ · FAXLine: (800) 548-6133 (US/Canada Only) · Cable: BBRCORP · Telex: 066-6491 · FAX: (520) 889-1510 · Immediate Product Info: (800) 548-6132

PCM1704

FEATURES

SAMPLING FREQUENCY (f

): 16kHz to 96kHz

8X OVERSAMPLING AT 96kHz

INPUT AUDIO DATA WORD: 20-, 24-Bit

HIGH PERFORMANCE:
Dynamic Range: K Grade = 112dB typ
SNR: 120dB typ
THD+N: K Grade = 0.0008% typ

FAST CURRENT OUTPUT:

1.2mA/200ns

GLITCH-FREE OUTPUT

PIN-PROGRAMMABLE DATA INVERSION

POWER SUPPLY:

SMALL 20-LEAD SO PACKAGE

PDS-1454C

Printed in U.S.A. February, 1999

DESCRIPTION

The PCM1704 is a precision, 24-bit digital-to-analog
converter with exceptionally high dynamic perfor-
mance. The ultra-low distortion and excellent low-
level signal performance makes the PCM1704 an ideal
candidate for high-end consumer and professional
audio applications. When used with a digital interpo-
lation filter, the PCM1704 supports 8X oversampling
at 96kHz.

The PCM1704 incorporates a BiCMOS sign-magni-
tude architecture that eliminates glitches and other
nonlinearities around bipolar zero. The PCM1704 is
precision laser-trimmed at the factory to minimize
differential linearity and gain errors.

In addition to high performance audio systems, the
PCM1704 is well-suited to waveform synthesis appli-
cations requiring very low distortion and noise.

Serial Input

and

Control Logic

Reference and Servo

REF DC SERVO DC

DGND +V

AGND

23-Bit DAC A

23-Bit DAC B

OUT

Bipolar Offset

INVERT

20-BIT

WCLK

DATA

BCLK

Power Supply

BPO DC

PCM1

704

PCM1704

SPECIFICATIONS

All specifications at T

= +25

5V, f

= 768kHz (96kHz · 8), and 24-bit data, unless otherwise noted.

PCM1704U

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

RESOLUTION

Bits

DATA FORMAT

Audio Data Interface Format

20-, 24-Bit, MSB-First

Audio Data Code

Binary Two's Complement

Sampling Frequency (f

)

kHz

Input Clock Frequency

MHz

DIGITAL INPUT/OUTPUT

Input Logic Level:

(1)

+2.0

+5.0

(1)

+0.8

(2)

3.0

(2)

5.0

4.2

Input Logic Current:

(1)

= +V

(1)

= 0V

(2)

= 0V

(2)

= V

100

DYNAMIC PERFORMANCE(3)

THD+N

= 0dB

PCM1704U

0.0025

0.0030

PCM1704U-J

0.0015

0.0025

PCM1704U-K

0.0008

0.0015

=20dB

PCM1704U

0.008

0.020

PCM1704U-J

0.007

0.015

PCM1704U-K

0.006

0.01

Dynamic Range

EIAJ, A-weighted

PCM1704U, U-J

102

110

PCM1704U-K

106

112

Signal-to-Noise Ratio

EIAJ, A-weighted

112

120

Low Level Linearity

f = 1002Hz at 90dB

0.5

DC ACCURACY

Gain Error

1.0

3.0

% of FSR

Bipolar Zero Error

0.5

1.0

% of FSR

Gain Drift

C to 70

ppm of FSR/

Bipolar Zero Error Drift

C to 70

ppm of FSR/

ANALOG OUTPUT

Output Range

1.2

Output Impedance

1.0

Settling Time

0.0003% of FSR,

1.2mA Step

200

POWER SUPPLY REQUIREMENTS

Voltage Range: +V

= +V

+4.75

+5.0

+5.25

VDC

= V

4.75

5.0

5.25

VDC

Combined Supply Current:+I

= +V

= +5.0V

= V

= 5.0V

TEMPERATURE RANGE

Operation

+85

Storage

+125

NOTES: (1) BCLK, WCLK, DATA. (2) 20BIT, INVERT. (3) Dynamic performance data is tested with 5534 I/V amp with 7.5k

feedback resistor. THD+N data is

tested by Shibasoku 725C with 30kHz external LPF, 400Hz HPF, average mode. Input signal frequency = 1.1kHz.

PCM1704

PIN ASSIGNMENTS

PIN CONFIGURATION

TOP VIEW

SOIC

PACKAGE INFORMATION

PACKAGE

TEMPERATURE

DRAWING

PRODUCT

PACKAGE

RANGE

NUMBER

(1)

PCM1704U

20-Lead SOIC

C to +85

248

NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book.

ABSOLUTE MAXIMUM RATINGS

Supply Voltage, +V

,+V

............................................................. +6.5V

Supply Voltage Differences ..............................................................

0.1V

GND Voltage Differences .................................................................

0.1V

Digital Input Voltage

(BCLK, WCLK, DATA) ............................ DGND 0.3V to (+V

+ 0.3V)

(20BIT, INVERT) .................................... V

0.3V to (DGND + 0.3V)

Input Current (any pins except supply pins) ...................................

10mA

Power Dissipation .......................................................................... 300mW
Operating Temperature Range ......................................... 25

C to +85

Storage Temperature ...................................................... 55

C to +125

Lead Temperature (soldering, 5s) ................................................. +260

Package Temperature (reflow, 10s) .............................................. +235

PIN

NAME

I/O

FUNCTION

DATA

Serial Audio Data Input.

BCLK

Bit Clock Input for Serial Audio Data.

No Connection.

Digital Power, 5V.

DGND

Digital Ground.

Digital Power, +5V.

WCLK

Data Latch Enable Input.

No Connection.

20BIT

Input Data Word Selection

(1)

INVERT

Input Data Polarity Selection

(1)

Analog Power, +5V.

BPO DC

Bipolar Offset Decoupling Capacitor.

No Connection.

OUT

Current Output for Audio Signal.

AGND

Analog Ground.

AGND

Analog Ground.

SERVO DC

Servo Amplifier Decoupling Capacitor.

No Connection.

REF DC

Band Gap Reference Decoupling Capacitor.

Analog Power, 5V.

NOTE: (1) Internal pull-up resistors. Input level must be a voltage from V

to DGND.

ELECTROSTATIC
DISCHARGE SENSITIVITY

This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.

ESD damage can range from subtle performance degradation
to complete device failure. Precision integrated circuits may
be more susceptible to damage because very small parametric
changes could cause the device not to meet its published
specifications.

PCM1704U

DATA

BCLK

DGND

WCLK

20BIT

INVERT

REF DC

SERVO DC

AGND

OUT

BPO DC

PCM1704

THEORY OF OPERATION

SIGN-MAGNITUDE ARCHITECTURE

Digital audio systems have traditionally used laser-trimmed,
current-source DACs in order to achieve sufficient accuracy.
However, even the best of these suffer from potential low-
level nonlinearity due to errors in the major carry bipolar
zero transition. Current systems have turned to oversampling
data converters, such as the popular delta-sigma architec-
tures, to correct the linearity problems. This is done, how-
ever, at the expense of signal-to-noise performance, and the
noise shaping techniques utilized by these converters creates
a considerable amount of out-of-band noise. If the outputs
are not properly filtered, dynamic performance of the overall
system will be adversely effected.

The PCM1704 employs an innovative architecture which
combines the advantages of traditional DACs (e.g., excellent
full-scale performance, high signal-to-noise ratio, and ease
of use) with superior low-level performance. This architec-
ture is referred to as sign-magnitude. Two DACs are com-
bined in a complementary arrangement to produce an ex-
tremely linear output. The two DACs share a common
reference, and a common R-2R ladder for bit current sources.
The R-2R ladder utilizes dual balanced current segments to
ensure ideal tracking under all conditions. By interleaving
the individual bits of each DAC and employing precision
laser-trimming of resistors, a highly accurate match between
the two DACs is achieved.

The sign-magnitude architecture, which steps away from
zero with small steps in both directions, avoids any glitching
or large linearity errors, and provides an absolute current
output. The low-level performance of the PCM1704 is such
that true 24-bit resolution can be realized around the critical
bipolar zero point.

DISCUSSION OF KEY
SPECIFICATIONS

TOTAL HARMONIC DISTORTION + NOISE (THD+N)

This is the key specification for the PCM1704. Digital data
words are read into the PCM1704 at eight times the standard
DVD audio sampling frequency of 96kHz (e.g., 8 x 96kHz =
768kHz) to create a sinewave output of 1100Hz. The output
of the DAC is then passed through analog signal conditioning
circuitry before being input to a distortion analyzer.

For production testing, the output of the DAC is connected
to a current-to-voltage (I/V) converter. The output of the
I/V converter is then connected to a 40kHz, 3rd-order GIC
low-pass filter. The filter output is then passed on to a
programmable gain amplifier to provide gain for low-level
test signals before being fed into an analog distortion
analyzer (Shiba Soku Model 725 or equivalent).

For the audio bandwidth, the THD+N for the PCM1704 is
essentially flat for all frequencies.

DYNAMIC RANGE

Dynamic range in data converters is specified as the measure
of THD+N at an effective output signal level of 60dBFS
(conforms to EIAJ method with A-weighting applied). Reso-
lution is commonly used as a theoretical measure of dy-
namic range, but it does not take into account the effects of
distortion and noise at low signal levels. The sign-magnitude
architecture of the PCM1704, with its ideal performance
around bipolar zero, provides a more usable dynamic range
(even with the strict audio definition) than any other previ-
ously available D/A converter.

IDLE CHANNEL SIGNAL-TO-NOISE RATIO (SNR)

Another important specification for a digital audio converter
is idle channel signal-to-noise ratio (Idle Channel SNR).
This is the ratio of the noise on the DAC output at bipolar
zero compared to the full-scale range of the D/A converter.
To make this measurement, the digital input is continually
fed the code for bipolar zero, while the output of the DAC
is band limited from 20Hz to 20kHz and A-weighting is
applied. The ideal channel SNR for the PCM1704 is typi-
cally greater than 120dB, making it ideal for low noise
applications.

OFFSET GAIN AND TEMPERATURE DRIFT

Although the PCM1704's primary application is in high
performance digital audio systems where dynamic specifica-
tions are most important, specifications are also given for
more traditional DC parameters. These include gain error,
bipolar zero offset, temperature gain and offset drift. These
specifications are important in test and measurement sys-
tems, which is the other main systems application for the
PCM1704.

PCM1704

AUDIO DATA INTERFACE

BASIC OPERATION

The audio interface of the PCM1704 accepts TTL-compat-
ible input levels. The data format at the DATA input of the
PCM1704 is Binary Two's Complement, with the most
significant bit (MSB) being first in the serial input bit steam.
Table I shows the relationship between the audio input data
and DAC output for the PCM1704. Any number of bits can
precede the 24 bits to be loaded since only the last 24 bits
will be transferred to the parallel DAC register after WCLK
(pin 7) has gone LOW (logic 0).

Maximum Bit Clock (BCLK) Rate

The maximum BCLK rate is specified as 25MHz. This is
derived from the 8X oversampling of the PCM1704. Given
a 96kHz sampling rate, an 8X oversampling input and a
32-bit frame length, we get:

96kHz · 8 · 32 = 24.576MHz

"Stopped Clock" Operation

The PCM1704 is normally operated with a continuous
BCLK input. If BCLK is stopped between input data words,
the last 24 bits shifted in are not actually transferred from the
serial register to the parallel DAC register until WCLK goes
LOW. WCLK must remain LOW until after the first BCLK
cycle of the next data word to insure proper DAC operation.
The specified setup and hold times for DATA and WCLK
must be observed.

DATA FORMAT CONTROL

Data format is controlled by two pins on the PCM1704--the
20BIT and INVERT inputs. Their functions are described in
the following paragraphs and tables.

Input Word Length

20BIT (pin 9) is used to select the input data length. Table
II shows the available selections. Pin 9 is internally pulled
up to DGND and therefore, defaults to 24-bit data.

BINARY TWO'S COMPLEMENT

INPUT DATA (Hex)

DAC OUTPUT

7FFFFF

+ Full Scale

000000

Bipolar Zero

FFFFFF

Bipoar Zero 1 LSB

800000

Full Scale

TABLE I. Digital Input/DAC Output Relationships.

Audio data is supplied to the DATA (pin 1) input. The bit
clock is used to shift data into the PCM1704 and is supplied
to BCLK (pin 2). All DAC serial input data bits are latched
into the serial input register on the rising edge of BCLK. The
serial-to-parallel data transfer to the DAC occurs on the
falling edge of WCLK. The change in the output of the DAC
occurs at the rising edge of the 2nd BCLK after the falling
edge of WCLK. Figure 1 shows the audio data input format.
Figure 2 shows the input timing relationships.

FIGURE 1. Audio Input Data Format.

BCH

BCY

BCL

WCH

WCL

1.4V

WCLK

BCLK

DATA

FIGURE 2. Audio Input Data Timing.

BCLK Pulse Cycle Time

BCY

40ns

(min)

BCLK Pulse Width HIGH

BCH

14ns

(min)

BCLK Pulse Width LOW

BCL

14ns

(min)

BCLK Rising Edge to WCLK Falling Edge

10ns

(min)

WCLK Falling Edge to BCLK Rising Edge

10ns

(min)

WCLK Pulse Width HIGH

WCH

> t

BCY

WCLK Pulse WIdth LOW

WCL

> t

BCY

DATA Set-up Time

10ns

(min)

DATA Hold Time

10ns

(min)

20BIT (Pin 9)

DATA WORD LENGTH

20BIT = H (DGND)

24-Bit Data Word

20BIT = L (V

)

20-Bit Data Word

TABLE II. Input Word Length Selection.

B1 B2 B3

B22 B23

MSB

LSB

B24

WCLK

DATA

DAC Output

BCK

DATA (20-Bit)

DATA (24-Bit)

LSB

B1 B2 B3

B18 B19

MSB

B20

PCM1704

Input Data Inversion

INVERT (pin 10) is used to select the phase of the input data
presented to the DAC. Table III shows the two options. Pin
10 is internally pulled up to DGND, and therefore defaults
to normal, or non-inverting data.

APPLICATIONS INFORMATION

POWER SUPPLIES

For this discussion, please refer to the internal connection
diagram for the PCM1704 in Figure 3. The PCM1704 only
requires a

5V supply for operation. Both positive supplies

(+V

and +V

) should be tied together at a single point

and connected to a single +5V analog power supply. Simi-
larly, both negative supplies (V

and V

) should be tied

at a single point and connected to a single 5V analog power

INVERT (Pin 10)

PHASE

INVERT = H (DGND)

Normal (non-inverted)

INVERT = L (V

)

Inverted

TABLE III. Input Data Phase Selection.

supply. No advantage is gained by using separate analog and
digital power supplies. It is more important that the analog
supplies used to drive these pins are as noise and ripple free
as possible to reduce coupling of supply noise to the output.

Power supply decoupling capacitors should be used at each
supply pin to maximize power supply rejection, as shown in
Figure 3. All ground pins (AGND and DGND) should be
connected to an analog ground plane as close to the PCM1704
as possible. The PCM1704 should reside entirely over the
analog ground plane of the printed circuit board.

Bypass and Decoupling Capacitor Requirements

Various-sized decoupling capacitors can be used, with no
special tolerances being required. Figure 5 shows typical
values used by Burr-Brown on our evaluation fixture, which
designers can use as recommended values. All capacitors
should be located as close to the appropriate pins of the
PCM1704 as possible to reduce noise pickup from sur-
rounding circuitry. Aluminum electrolytic capacitors are
recommended for larger values, while metal-film or mono-
lithic ceramic capacitors are used for smaller values.

FIGURE 3. PCM1704 Internal Connection Diagram.

Interface

Logic

and

Logic Bias

23-Bit

Segment
Switches

Reference,

Servo

and

Bipolar

Offset

Analog

Bias

Logic

Bias

23-Bit

Current

Segments

BPO

DGND

AGND

OUT

BCLK

WCLK

DATA

+5V Supply

BPO DC

SERVO DC

REF DC

5V Supply

2mA

3mA

20mA

10mA

PCM1704

FIGURE 4. Audio Interface Connections for Stereo Audio

Application.

FIGURE 5. Typical Application Circuit (one channel shown).

DOR

WCKO

BCKO

DOL

DATA

WCLK

BCLK

DATA

WCLK

BCLK

DF1704 or Other

Digital Filter

PCM1704

24-Bit

96kHz

Data

TYPICAL APPLICATION
EXAMPLES

The audio interface connections for a stereo audio applica-
tion is shown in Figure 4. The audio data is input to the
digital filter, which then oversampleS the data by a factor of
8. The audio data is then filtered digitally and output to the
PCM1704 DACs.

Figure 5 shows single channel circuit connections for a
typical PCM1704 application. It shows the PCM1704 inter-
face to the digital filter, the I/V converter, and the DAC post
filter. Selection of an appropriate op amp for the I/V con-
verter is critical for obtaining optimum dynamic perfor-
mance from the PCM1704. The OPA627 is recommended
for this application. Op amps with similar characteristics and
faster settling times may also be used.

The suggested DAC post filter is a second-order lowpass
active filter, using the multiple feedback (MFB) circuit
technique. The OPA2134 is an excellent choice for the op
amp in this circuit, since it is designed for high performance
audio applications. The post filter is used to reconstruct and
band limit the DAC output signal.

Digital

Controls

Aluminum

Electrolytics

100

0.1

4.7

OPA627

1/2

OPA2134

47pF

4.7

100

0.1

100

0.1

+5V

15V

Audio

Output

+15V

100

0.1

PCM1704U

DATA

BCLK

DGND

WCLK

20BIT

INVERT

REF DC

SERVO DC

AGND

OUT

BPO DC

Oversampling

Interpolation

Filter

2.5k

4.7k

4.7

560pF

2200pF

4.7

DAC

I/V

Post Filter

24-Bit

96kHz Data

= 4.7

= 47

= 100

= 4.7

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: PCM1704U

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: PCM1704U