Instruction Manual

DS882F1 75

CS42L73

4.18 Headphone High-Impedance Mode

During normal operation, the headphone output pins are driven by the CS42L73 with low impedance drivers

to support low impedance loads. While the headphone amplifier is powered down, the headphone output

pins are clamped to ground to prevent undesired transients. Systems that support headset jack–type detec-

tion with an external circuit may require the headphone output pins to be in a high-impedance state to prop-

erly detect the connected headset type. To accommodate this case, the headphone output pins can be

placed into a high-impedance state while the headphone amplifier is powered down. Once the headset type

detection has completed, the headphone output pins should be returned to the normal-impedance mode.

To enable high-impedance mode, perform the following sequence of register writes:

1. Power down the headphone amplifier by following Section 4.12.3 through Step 3.

2. Register 00h = 99h

3. Register 7Eh = 96h

4. Register 7Fh = 95h

5. Register 00h = 00h

To disable high-impedance mode, perform the following sequence of register writes:

1. Register 00h = 99h

2. Register 7Eh = 96h

3. Register 7Fh = 94h

4. Register 00h = 00h

Table 14. Start Up Transition Values

Output Path

t1 t2

Unit

Normal Mode Fast Start Mode Normal Mode Fast Start Mode

HPOUT/LINEOUT65257030ms

EAR SPKOUT 40 35 46 180 ms

SPKLINEOUT 140 45 500 500 ms

SPKOUT 140 45 700 700 ms

PDN

t = 0

Normal audioNo audio

Clipped/Ramping audio

Output

Figure 41. Start Up Transition Diagram