AD1847JP Analog Devices Inc, AD1847JP Datasheet - Page 23
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AD1847JP
Manufacturer Part Number
AD1847JP
Description
Manufacturer
Analog Devices Inc
Datasheet
1.AD1847JP.pdf
(28 pages)
Specifications of AD1847JP
Single Supply Voltage (typ)
5V
Single Supply Voltage (min)
4.75V
Single Supply Voltage (max)
5.25V
Package Type
PLCC
Lead Free Status / RoHS Status
Not Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
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Part Number:
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Manufacturer:
AD
Quantity:
5 510
Part Number:
AD1847JP
Manufacturer:
ADI/亚德诺
Quantity:
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REV. B
DATA FORMAT DEFINITIONS
There are four data formats supported by the AD1847: 16-bit
signed, 8-bit unsigned, 8-bit companded -law, and 8-bit com-
panded A-law. The AD1847 supports these four formats because
each of them have found wide use in important applications.
16-Bit Signed Format
The 16-bit signed format (also called 16-bit twos-complement)
is the standard method of representing 16-bit digital audio. This
format yields 96 dB of dynamic range and is common in con-
sumer compact disk audio players. This format uses the value
– 32768 (8000h) to represent minimum analog amplitude while
32767 (7FFFh) represents maximum analog amplitude. Inter-
mediate values are a linear interpolation between minimum and
maximum amplitude values.
8-Bit Unsigned Format
The 8-bit unsigned format is commonly used in the personal
computer industry. This format delivers 48 dB of dynamic
range. The value 0 (00h) is used to represent minimum analog
amplitude while 255 (FFh) is used to represent maximum ana-
log amplitude. Intermediate values are a linear interpolation be-
tween minimum and maximum amplitude values. The least
significant byte of the 16-bit internal data is truncated to create
the 8-bit output samples.
MAX
MAX
MIN
MIN
00h
8000h
Figure 12. 8-Bit Unsigned Format
Figure 11. 16-Bit Signed Format
DIGITAL VALUE
DIGITAL VALUE
0000h
7Fh
7FFFh
FFh
–23–
8-Bit Companded Formats
The 8-bit companded formats ( -law and A-law) are used in the
telecommunications industry. Both of these formats are used in
ISDN communications and workstations; -law is the standard
for the United States and Japan while A-law is used in Europe.
Companded audio allows either 64 dB or 72 dB of dynamic
range using only 8-bits per sample. This is accomplished using a
nonlinear formula which assigns more digital codes to lower am-
plitude analog signals at the expense of resolution of higher am-
plitude signals. The -law format of the AD1847 conforms to
the Bell System = 255 companding law while the A-law format
conforms to CCITT “A” law models. Figure 13 shows approxi-
mately how both the -law and A-law companding schemes be-
have. Refer to the standards mentioned above for an exact
definition.
APPLICATIONS CIRCUITS
The AD1847 Stereo Codec has been designed to require a mini-
mum of external circuitry. The recommended circuits are shown
in Figures 14 through 22. Analog Devices estimates that the to-
tal cost of all the components shown in these Figures, including
crystals, to be less than $3 in 10,000 quantities.
Industry-standard compact disc “line-levels” are 2 V
around analog ground. (For other audio equipment, “line level”
is much more loosely defined.) The AD1847 SoundPort is a
+5 V only powered device. Line level voltage swings for the
AD1847 are defined to be 1 V
0.707 V
log signals must be attenuated and either centered around the
reference voltage intermediate between 0 V and +5 V or
ac-coupled. The V
nominally 2.25 V. It has limited drive but can be used as a volt-
age datum to an op amp input. Note, however, that dc-coupled
inputs are not recommended, as they provide no performance
benefits with the AD1847 architecture. Furthermore, dc offset
differences between multiple dc-coupled inputs create the po-
tential for “clicks” when changing the input mux selection.
MAX
MIN
rms
00h
2Ah
for a sine wave DAC output. Thus, 2 V
Figure 13. 8-Bit Companded Format
REF
pin will be at this intermediate voltage,
DIGITAL VALUE
FFh
D5h
rms
for a sine wave ADC input and
AD1847
rms
AAh
80h
rms
input ana-
centered
µ-law
A-law