cm
pop
load
load
load
V
R
R
R
V
´
+
=
Rload
Rpop
Cc
Output
Driver
PAD
Analog Audio I/O
The left and right DAC channels are routed to the corresponding left and right headphone amplifier. This
configuration is also used to drive line-level loads.
The TLV320DAC3203 headphone drivers support pop-free operation. Because the HPL and HPR are
high-power drivers, pop can result due to sudden transient changes in the output drivers if care is not
taken. The most critical care is required while using the drivers as stereo single-ended capacitively-
coupled drivers as shown in
. The output drivers achieve pop-free power-up by using slow
power-up modes. Conceptually, the circuit during power-up can be visualized as
Figure 2-3. Conceptual Circuit for Pop-Free Power-up
The value of R
pop
can be chosen by setting register Page 1, Register 20, Bits D1-D0).
Table 2-3. R
pop
Values
Page 1, Register 20, Bits D1-D0)
R
pop
Value
00
2 k
Ω
01
6 k
Ω
10
25 k
Ω
To minimize audible artifacts, two parameters can be adjusted to match application requirements. The
voltage V
load
across R
load
at the beginning of slow charging should not be more than a few mV. At that time
the voltage across R
load
can be determined as:
(1)
For a typical R
load
of 32
Ω
, R
pop
of 6 k
Ω
or 25 k
Ω
will deliver good results (see
for register
settings).
According to the conceptual circuit in
, the voltage on PAD will exponentially settle to the output
common-mode voltage based on the value of R
pop
and C
c
. Thus, the output drivers must be in slow power-
up mode for time T, such that at the end of the slow power-on period, the voltage on V
pad
is very close to
the common-mode voltage. The TLV320DAC3203 allows the time T to be adjusted to allow for a wide
range of R
load
and C
c
by programming Page 1, Register 20, Bits D5-D2). For the time adjustments, the
value of C
c
is assumed to be 47
μ
F. N=5 is expected to yield good results.
Page 1, Register 20, Bits D5-
Slow Charging Time=N*Time – Constants(for R
pop
and 47
μ
F)
D2)
0000
N=0
0001
N=0.5
0010
N=0.625
0011
N=0.75
0100
N=0.875
0101
N=1.0
0110
N=2.0
0111
N=3.0
1000
N=4.0
1001
N=5.0
17
SLAU434 – May 2012
TLV320DAC3203 Application
Copyright © 2012, Texas Instruments Incorporated