CS47L35 datasheet(159/300 Pages) CIRRUS

159 / 300 page

DS1085F3

159

CS47L35

4.12 External Accessory Detection

Note that, for typical headset detection, the choice of external resistance values must take into account the impedance of

the microphone—the detected impedance corresponds to the combined parallel resistance of the microphone and any

asserted push button.

4.12.4 Headphone Detect

The CS47L35 headphone detection circuit measures the impedance of an external headphone load. This feature can be

used to set different gain levels or to apply other configuration settings according to the type of load connected. Separate

monitor pins are provided for headphone detection on the left and right channels of HPOUT.

4.12.4.1 Headphone Detection Control

Headphone detection can be enabled on the HPDETL pin or the HPDETR pin. Under recommended configuration, these

pins provide measurement of the HPOUTL and HPOUTR loads respectively.

The headphone detect function can also be enabled on the MICDET1 pin or the MICDET2 pin. Note that, in this

configuration, any MICBIAS output that is connected to the selected MICDET pin must be disabled and floating (MICBnx_

ENA = 0, MICBnx_DISCH = 0).

The applicable headphone detection pin is selected using the ACCDET_MODE field. When MICDETn is selected

(ACCDET_MODE = 100), the applicable MICDETn pin is determined by the ACCDET_SRC bit, as described in

Table 4-80.

The CS47L35 can only support one headphone or microphone detection function at any time. When the detection function

is not in use, it is recommended to set ACCDET_MODE = 000.

Headphone detection on the selected channel is commanded by writing 1 to HP_POLL.

The impedance measurement range is configured using HP_IMPEDANCE_RANGE. This field should be set in

accordance with the expected load impedance. Note that a number of separate measurements are typically required to

determine the load impedance; the recommended control requirements are described in Section 4.12.4.2.

Note: Setting HP_IMPEDANCE_RANGE is not required for detection on the MICDETn pins (ACCDET_MODE = 100).

The impedance measurement range, and measurement accuracy, in this mode are different to the HPDETL and

HPDETR measurement modes.

For correct operation, the respective output drivers must be disabled when headphone detection is commanded on

HPOUTL or HPOUTR. The required settings are shown in Table 4-78.

When headphone detection is commanded, the CS47L35 uses an adjustable current source to determine the connected

impedance. A sweep of measurement currents is applied. The rate of this sweep can be adjusted using HP_CLK_DIV and

HP_RATE.

4.12.4.2 Measurement Output

The headphone detection process typically comprises a number of separate measurements (for different impedance

ranges). Completion of each measurement is indicated by HP_DONE. When this bit is set, the measurement result can

be read from the HP_DACVAL and HP_DACVAL_DOWN fields, and decoded as described in Eq. 4-2.

Table 4-78. Output Configuration for Headphone Detect

Description

Requirement

HPOUTL Impedance measurement

HP1L_ENA = 0

HPOUTR Impedance measurement

HP1R_ENA = 0

Note: The applicable headphone outputs configuration must be maintained until after the headphone

detection has completed. See Table 4-64 for details of the HP1L_ENA and HP1R_ENA bits.

CS47L35 датащи(PDF) 159 Page - Cirrus Logic

CS47L35 датащи(HTML) 159 Page - Cirrus Logic

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL