AD1853 View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD1853 Datasheet PDF : 16 Pages
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Table III. Digital Timing
Min
tCCH
CCLK HI Pulsewidth
40
tCCL
CCLK LOW Pulsewidth
40
tCSU
CDATA Setup Time
10
tCHD
CDATA Hold Time
10
tCLL
CLATCH LOW Pulsewidth
10
tCLH
CLATCH HI Pulsewidth
10
AD1853
Units
ns
ns
ns
ns
ns
ns
SPI REGISTER DEFINITIONS
VOLUME LEFT and VOLUME RIGHT Registers
The SPI port allows flexible control of many chip parameters.
It is organized around three registers; a LEFT-CHANNEL
VOLUME register, a RIGHT-CHANNEL VOLUME register
and a CONTROL register. Each WRITE operation to the
AD1853 SPI control port requires 16 bits of serial data in
MSB-first format. The bottom two bits are used to select one
E of three registers, and the top 14 bits are then written to that
register. This allows a write to one of the three registers in a
single 16-bit transaction.
T The SPI CCLK signal is used to clock in the data. The incom-
ing data should change on the falling edge of this signal. At the
end of the 16 CCLK periods, the CLATCH signal should rise
to latch the data internally into the AD1853.
E Register Addresses
The lowest two bits of the 16-bit input word are decoded as
follows to set the register into which the upper 14 bits will be
L written.
Bit 1
0
O 1
OBS 0
Bit 0
0
0
1
Register
Volume Left
Volume Right
Control Register
A write operation to the left or right volume registers will acti-
vate the “auto-ramp” clickless volume control feature of the
AD1853. This feature works as follows. The upper 10 bits of
the volume control word will be incremented or decremented by
1 at a rate equal to the input sample rate. The bottom 4 bits are
not fed into the auto-ramp circuit and thus take effect immedi-
ately. This arrangement gives a worst-case ramp time of about
1024/FS for step changes of more than 60 dB, which has been
determined by listening tests to be optimal in terms of pre-
venting the perception of a “click” sound on large volume
changes. See Figure 8 for a graphical description of how the
volume changes as a function of time.
The 14-bit volume control word is used to multiply the signal,
and therefore the control characteristic is linear, not dB. A con-
stant dB/step characteristic can be obtained by using a lookup
table in the microprocessor that is writing to the SPI port.
0
VOLUME REQUEST REGISTER
–60
0
ACTUAL VOLUME REGISTER
–60
20ms
TIME
Figure 8. Smooth Volume Control
REV. A
–9–
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