CS4399 datasheet(28/111 Pages) CIRRUS

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DS1113F1

CS4399

4.4 Headphone Presence Detect

4.4.1

Headphone Presence Detect

The CS4399 supports headphone presence-detect capability via the HP_DETECT sense pin. HP_DETECT is debounced

to filter out brief events before being reported to the corresponding presence-detect status bit and generating an interrupt

if appropriate.

4.4.1.1 Headphone Detect Methods

CS4399 can detect the presence or absence of a plug. For a headphone-presence detect, a sense pin is connected to a

terminal on the receptacle such that, if no plug is inserted, the pin is floating. If a plug is inserted, the pin is shorted to the

tip (T) terminal. The presence detect function is accomplished by having a small current source inside the CS4399 to pull

up the pin if it is left floating (no plug). If a plug is inserted and the sense pin is shorted to headphone output, the sense

pin is shorted to the output signal and, therefore, is pulled below a certain threshold via the output stage of the HP amp.

Thus, a low level at the sense pin indicates plug inserted, and a high level at the sense pin indicates plug removed.

4.4.1.2 Headphone Detect Registers

This section describes the behavior and interaction of the headphone-detect debounce register fields. See Fig. 4-8 for

reference.

Figure 4-8. Headphone Detect Block Diagram

• HPDETECT_CTRL configures the operation of the HP detect circuit.

• HPDETECT_INV inverts the signal from the HP detect circuit.

• HPDETECT_FALL_DBC_TIME configures the HP_DETECT falling debounce time.

• HPDETECT_RISE_DBC_TIME configures the HP_DETECT rising debounce time.

• HPDETECT_PLUG_DBC shows the falling-edge-debounced version of HP_DETECT signal.

• HPDETECT_UNPLUG_DBC shows the rising-edge-debounced version of HP_DETECT signal.

• HPDETECT_PLUG_INT shows the headphone plug-in event status.

• HPDETECT_UNPLUG_INT shows the headphone unplug event status.

• HPDETECT_PLUG_INT_MASK is the interrupt mask of headphone plug-in event status.

• HPDETECT_UNPLUG_INT_MASK is the interrupt mask of headphone unplug event status.

4.4.1.3 Headphone Detect and Interrupts Setup Instructions

The following steps are required for activation of headphone-detect debounce interrupt status:

1. Ensure the I2C is ready to respond to control port command.

2. Clear the interrupt masks.

HP_DETECT

HP Detect Block

Delay

HP Detect

Plug/Unplug

Detect

HP Detect

Plug/Unplug Interrupt

Mask

HP Detect

Plug/Unplug Interrupt

Status

Interrupt Handler Block

INT

Read

Deasserts INT

FALL_DEBOUNCE

RISE DEBOUNCE

Delay

HP Detect

Debounced Status

HPDETECT_CTRL p. 89

HPDETECT_PLUG_INT

p. 90

HPDETECT_UNPLUG_

INT p. 90

HPDETECT_RISE_DBC_TIME p. 89

HPDETECT_FALL_DBC_TIME p. 89

HPDETECT_INV p. 89

HPDETECT_PLUG_DBC p. 89

HPDETECT_UNPLUG_DBC p. 90

HPDETECT_PLUG_INT_

MASK p. 92

HPDETECT_UNPLUG_

INT_MASK p. 92

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