LM4935RLEVAL datasheet(36/91 Pages) TI1

36 / 91 page

LM4935, LM4935RLEVAL

SNAS296D – OCTOBER 2005 – REVISED MARCH 2006

www.ti.com

Table 4-29. DETECT (0x17h) (continued)

Bits

Field

Description

6:3

HS_

Sets the time used for debouncing the analog signals from the detection inputs used to sense the

DBNC_TIME

insertion/removal of a headset.

HS_DBNC_TIME

Time (ms)

00002

00012

00102

00112

01002

01012

01102

01112

128

10002

192

10012

256

10102

384

10112

512

11002

768

11012

1024

11102

1536

11112

2048

4.2.29 HEADSET DETECT OVERVIEW

The LM4935 has built in monitors to automatically detect headset insertion or removal. The detection

scheme can differentiate between mono, stereo, mono-cellular and stereo-cellular headsets. Upon

detection

headset

insertion

removal,

the

LM4935

updates

read-only

bit

headset

absence/presence, bit 1- mono/stereo headset and bit 2 - headset without mic / with mic, of the STATUS

consumes no analog supply current when the headset is absent.

The LM4935 can be programmed to raise an interrupt (set the IRQ pin high) when headset insert/removal

is sensed by setting bit 0 of DETECT (0x17h). When headset detection is enabled in active mode and a

headset is not detected, the HPL_OUT and HPR_OUT amplifiers will be disabled (switched off for capless

mode and muted for AC-coupled mode) and the EXT_BIAS pin will be disconnected from the MIC_BIAS

amplifier, irrespective of control register settings.

The LM4935 also has the capability to detect button press, when a button is present on the headset

microphone. Both parallel button-type (in parallel with the headset microphone, default value) and series

button-type (in series with the headset microphone) can be detected; the button type used needs to be

defined in bit 3 of MIC_2 (0x0Ch). Button press can also be detected in stand-by mode; this consumes 10

µA of analog supply current for a series type push button and 100 µA for a parallel type push button. Upon

button press, the LM4935 updates bit 3 of STATUS (0x18h). In active OCL mode, with internal

microphone selected (INT_EXT = 0; (reg 0x0Bh)), if a parallel pushbutton headset is inserted into the

system, INT_EXT must be set high before BTN (bit 3 of STATUS (0x18h)) can be read. The LM4935 can

also be programmed to raise an interrupt on the IRQ pin when button press is sensed by setting bit 1 of

DETECT.

The

LM4935

provides

debounce

programmability

for

headset

and

button

detect.

Debounce

programmability can be used to reject glitches generated, and hence avoid false detection, while

inserting/removing a headset or pressing a button.

Headset insert/removal debounce time is defined by HS_DBNC_TIME; bits 6:3 of DETECT (0x17h).

Parallel button press debounce time is defined by BTN_DBNC_TIME; bits 5:4 of MIC_2 (0x0Ch).

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