Analog Audio I/O
Page 1, Register 20, Bits D5-
Slow Charging Time=N*Time – Constants(for R
pop
and 47
μ
F)
D2)
1010
N=6.0
1011
N=7.0
1100
N=8.0
1101
N=16 (Not valid for R
pop
=25k
Ω
)
1110
N=24 (Not valid for R
pop
=25k
Ω
)
1111
N=32 (Not valid for R
pop
=25k
Ω
)
Again, for example, for R
load
=32
Ω
, C
c
=47
μ
F and common mode of 0.9V, the number of time constants
required for pop-free operation is 5 or 6. A higher or lower C
c
value will require higher or lower value for N.
During the slow-charging period, no signal is routed to the output driver. Therefore, choosing a larger than
necessary value of N results in a delay from power-up to signal at output. At the same time, choosing N to
be smaller than the optimal value results in poor pop performance at power-up.
The signals being routed to headphone drivers (e.g. DAC and IN) often have DC offsets due to less-than-
ideal processing. As a result, when these signals are routed to output drivers, the offset voltage causes a
pop. To improve the pop-performance in such situations, a feature is provided to soft-step the DC-offset.
At the beginning of the signal routing, a high-value attenuation can be applied which can be progressively
reduced in steps until the desired gain in the channel is reached. The time interval between each of these
gain changes can be controlled by programming Page 1, Register 20, Bits D7-D6). This gain soft-stepping
is applied only during the initial routing of the signal to the output driver and not during subsequent gain
changes.
Page 1, Register 20, Bits D7-D6 Soft-stepping Step Time During initial signal routing
00
0 ms (soft-stepping disabled)
01
50ms
10
100ms
11
200ms
It is recommended to use the following sequence for achieving optimal pop performance at power-up:
1. Choose the value of R
pop
, N (time constants) and soft-stepping step time for slow power-up.
2. Choose the configuration for output drivers, including common modes and output stage power
connections
3. Select the signals to be routed to headphones.
4. Power-up the blocks driving signals into HPL and HPR, but keep it muted
5. Unmute HPL and HPR and set the desired gain setting.
6. Power-on the HPL and HPR drivers.
7. Unmute the block driving signals to HPL and HPR after the Driver PGA flags are set to indicate
completion of soft-stepping after power-up. These flags can be read from Page 1, Register 63, Bits D7-
D6).
It is important to configure the Headphone Output driver depop control registers before powering up the
headphone; these register contents should not be changed when the headphone drivers are powered up.
Before powering down the HPL and HPR drivers, it is recommended that user read back the flags in Page
1, Register 63. For example. before powering down the HPL driver, ensure that bit D(7) = 1 and bit D(3) =
1 if INL is routed to HPL and bit D(1) = 1 if the Left Mixer is routed to HPL. The output driver should be
powered down only after a steady-state power-up condition has been achieved. This steady state power-
up condition also must be satisfied for changing the HPL/R driver mute control in Page 1, Register 16 and
17, Bits D7), i.e. muting and unmuting should be done after the gain and volume controls associated with
routing to HPL/R finished soft-stepping.
In the differential configuration of HPL and HPR, when no coupling capacitor is used, the slow charging
method for pop-free performance need not be used. In the differential load configuration for HPL and
HPR, it is recommended to not use the output driver MUTE feature, because a pop may result.
18
TLV320DAC3203 Application
SLAU434 – May 2012
Copyright © 2012, Texas Instruments Incorporated
