Datasheet

47:

g m s

Stereo +

Cellular

47:

g m

Cellular

g s

Stereo

g m s

Stereo +

Cellular

g m

Cellular

LM49370

www.ti.com

SNAS356D –FEBRUARY 2007–REVISED MARCH 2012

The LM49370 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

LM49370 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 LM49370 can also be programmed to raise an interrupt on the

IRQ pin when button press is sensed by setting bit 1 of DETECT (0x17h).

The LM49370 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).

Note that since the first effect of a series button press (microphone disconnected) is indistinguishable from

headset removal, the debounce time for series button press in defined by HS_DBNC_TIME.

Headset and push button detection can be enabled by setting CHIP_MODE 0; bit 0 of BASIC (0x00h). For

reliable headset / push button detection all following bits should be defined before enabling the headset detection

system:

1. the OCL-bit (AC-Coupled / Capless headphone interface (bit 6 of HP_OUTPUT (0x15h))

2. the headset insert/removal debounce settings (bit 6:3 of DETECT (0x17h))

3. the BTN_TYPE-bit (Parallel / Series push button type (bit 3 of MIC_2 (0x0Ch))

4. the parallel push button debounce settings (bit 5:4 of MIC_2 (0x0Ch))

Figure 16 shows terminal connections and jack configuration for various headsets. Care should be taken to avoid

any DC path from the MIC_DET pin to ground when a headset is not inserted.

Figure 16. Headset Configurations Supported by the LM49370

Product Folder Links: LM49370