ADAU1373BCBZ-R7 datasheet(44/296 Pages) AD

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ADAU1373

Rev. 0 | Page 44 of 296

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.

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 logic change of the JACKDET pin is reported in Bit 4,

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.

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.

Table 10. Headphone/Speaker Amplifier Control Settings

JACKDET

Pin Status

Reg. 0x36,

Bit 1

Reg. 0x36,

Bit 0

Headphone

Amplifier

Status

Speaker

Amplifier

Status

No change

Power-down

No change

Power-down

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.

No change

1 X = don’t care.

The amplifier output level can be controlled using Register 0x0D

(speaker out left gain control) and Register 0x0E (speaker out

right gain control).

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

The amplifier can be set to work in mono or stereo mode using

are mixed before being output to the speaker. The summed signal

can be made available to either the left or right speaker output.

SPEAKER OUTPUT

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 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

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).

2kΩ

AINxP

2.5mm/3.5mm

MINI JACK

PCB

ADAU1373

JACK EVENT

DETECT

PROG

MIC-BIAS2

MIC-PRE2

HP-L

HP-R

JACKDET

MICBIASx

HPL

HPR

SGND

1µF

SPKVDD

100kΩ

TYP

Figure 90. Headphone Jack Detect Option 2

ADAU1373BCBZ-R7 Datasheet(PDF) 44 Page - Analog Devices

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