AS3525 datasheet(131/194 Pages) AMSCO

131 / 194 page

AS3525-A/-B C22O22

Data Sheet, Confidential

www.austriamicrosystems.com

Revision 1.13

131

- 194

7.4.6

Headphone Output

7.4.6.1

General

The headphone output is designed to provide the audio signal with 2x40mW @ 16

Ω or 2x20mW @32Ω, which are typical values for headphones.

This output stage has an independent gain regulation for left and right channel with 32 steps @ 1.5dB each. The gain can be set from –43.43dB to

+1.07dB. The maximum output power of 40mW @ 16

Ω is achieved, by setting the mixer output to 1Vp and using the gain of 1.07dB.

Figure 50 Headphone Output

Headphones connected via decoupling capacitors

Headphones connected to Phantom Ground

(Common Mode)

7.4.6.2

Phantom Ground

HPCM pin is the buffered HPGND output. It can be used to drive the loads without external blocking capacitors between HPL / HPR and HPCM. If

the load is between HPR / HPL and BVSS, 100uF of de-coupling capacitors are needed. The phantom ground can be switched off to save power if

not needed.

7.4.6.3

No-Pop Function

To avoiding click and pop noise during power-up and shutdown, the output is automatically set to mute when the output stage is disabled.

HPGND pin, which needs a 100nF capacitor outside, gets charged on power-up with 2uA to AGND=1.45V. After start-up the DC level of the

following pins are the same: HPR=HPL=HPCM=HPGND=AGND=1.45V. The Start-up time before releasing mute is about 90ms. To avoid pop-

noise 150ms discharging time of HPGND after a shutdown, have to be waited before starting up again.

7.4.6.4

Over-current Protection

This output stage has an over-current protection, which disables the output for 256ms or 512ms. This value can be set in the headphone registers.

The over-current protection limit of HPR and HPL pin is typical 145mA while HPCM pin has a 210mA threshold. If needed, the over-current

condition can also be signalled via an interrupt to the controlling microprocessor.

7.4.6.5

Headphone Detection

With a control bit the headphone detection can be enabled. The detection is only working as long as the headphone stage is in power down mode

and the load is applied between HPR / HPL and HPCM. The headphone detection can also trigger a corresponding interrupt.

AS3525 Datasheet(PDF) 131 Page - ams AG