adau1373 Analog Devices, Inc., adau1373 Datasheet - Page 44

• Manufacturer Part Number: adau1373
• Description: Low Power Codec With Speaker And Headphone Amplifier Adau1373
• Manufacturer: Analog Devices, Inc.

ADAU1373
Figure 90 shows another option for similar functionality. The
circuit in Figure 90 does not use the amplifier to pull down the
JACKDET pin (Ball G5); instead, it uses an isolated switch in
the headphone jack.
The logic change of the JACKDET pin is reported in Bit 4,
Register 0x38. In addition, the debounced version of the logic
change is provided in Register 0xE6, Bit 1. Register 0x36 can be
used to control the state of the headphone amplifier and speaker
amplifier. Table 10 lists the possible settings.
Table 10. Headphone/Speaker Amplifier Control Settings
JACKDET
Pin Status
X
1
0
1
0
1
For example, if Register 0x36, Bits[1:0] = 10 and JACKDET
is high, the headphone amplifier is shut down, and the speaker
amplifier status is unchanged. Note that the headphone or
speaker amplifier cannot be turned on automatically, based
on a JACKDET pin event. The amplifiers must be enabled via
Register 0x27, a power management register.
SPEAKER OUTPUT
The ADAU1371 provides stereo Class-D amplifier outputs to
drive the speakers directly. The three-level switching scheme
allows the speaker load to be connected directly without any
output filters; it also reduces idle power consumption and EMI by
reducing switching. The amplifier outputs are differential and use
full bridge topology. The amplifier has basic protections, such as
the output short to SPKVDD, SPKGND, and the SPKxP and
X = don’t care.
1
Reg. 0x36,
Bit 1
0
1
1
1
1
Reg. 0x36,
Bit 0
X
0
0
1
1
1
MIC-BIAS2
ADAU1373
MIC-PRE2
Headphone
Amplifier
Status
No change
Power-down
No change
Power-down
No change
HP-R
HP-L
PROG
Figure 90. Headphone Jack Detect Option 2
JACK EVENT
Speaker
Amplifier
Status
No change
No change
Power-down
Power-down
No change
DETECT
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AINxP
JACKDET
MICBIASx
HPL
HPR
SGND
1µF
2kΩ
SPKxN outputs. In addition, it monitors the junction temperature
internally and shuts down if the temperature exceeds 150°C ±
15°C. In fault situations, the amplifier is switched to high-Z
mode for safe and reliable operation.
The amplifier uses three-level PDM switching and an analog
modulator with internal feedback. This method ensures good
PSRR on the outputs. Three-level switching eliminates the need
for an external output filter for connecting the speakers. However,
it is important to ensure that the speakers be placed within 10 cm
from the ADAU1373 to reduce EMI from the switching outputs.
For best EMI performance, proper board layout is required. It is
recommended that the supply voltage pins (G1, G2, H2, and
H3) be decoupled to SPKGND (H4, H5, J1, and J5) with two
100 nF, X7R ceramic capacitors.
The high efficiency amplifier outputs reduce power dissipation;
however, thermal performance depends on layout of the board.
The amplifier receives the input from the speaker mixer and
includes a circuit to prevent pop-and-click during turn off and
turn on.
The amplifier output level can be controlled using Register 0x0D
(speaker out left gain control) and Register 0x0E (speaker out
right gain control).
The amplifier can be set to work in mono or stereo mode using
Register 0x1F. In mono mode, the left and right channel signals
are mixed before being output to the speaker. The summed signal
can be made available to either the left or right speaker output.
Register 0x1F, Bits[5:4] can be used to set the mono amplifier
mode for higher output current capability to drive low impedance
loads. In this mode, the left and right channel output FETs are
fed from one modulator only. The corresponding left and right
channel outputs must be connected externally to take advantage
of the low impedance drive capability.
The default amplifier gain is 12 dB; it can be changed to 18 dB
using Register 0x1F, Bit 3 (right channel) and Bit 2 (left channel).
SPKVDD
PCB
100kΩ
TYP
2.5mm/3.5mm
MINI JACK