Analog Devices ADAV4601 System Design Document page 16

This is disabled in this register write, and the Vref is powered up at a gradual rate to ensure no pop is audible at the
output.
This register write powers up the Auxiliary DACs; AUXDAC1 and AUXDAC3. It also powers up the DAC internal
reference buffer and puts all DACs into normal mode.
This register write powers up the headphone 1 amplifiers as well as the headphone 1 DACs.
Note: AUXDAC4 and headphone 1 are connected together. Therefore, to use AUXDAC4, headphone 1 must be
powered up.
Note: Theses two writes power up all available DACs on the ADAV4601. In power critical applications or depending
on the number of DACs required, the user can power up the minimum number of DACs needed for operation.
This write disables the tri-state on the headphone. By default the headphone outputs are tri-stated. This register
write enables the headphone outputs for normal use.
This register write adjusts the current to the Vref charger circuit. By writing this, it changes the initial change in the
Vref charge profile to a much more gradual increase, which further decreases the chances of hearing any pops on
the output of the ADAV4601. For more information on the Vref charger circuit, refer to Figure 9.
This register write, enables the Vref charger circuitry which when set allows the gradual charging of the Vref voltage
from 0V up to 1.5V in an S shaped profile, which ensures that there are no sharp current spikes at the output of the
part, which would otherwise cause noise. See Figure 8 for more details.
ADAV4601 System Design Document
Rev.1 August 2009
Ipeak Ipeak
Vref Vref
10uF 10uF 560 560
DC blocking Cap DC blocking Cap
Figure 7: Vref powered up instantaneously
34 0005 A06F
34 0006 023F
34 000B 2020
34 0329 0400
34 008D 06BA
Analog Devices
Speaker out Speaker out
RL RL
5.6nF 5.6nF
(10K) (10K)
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