WM8959 datasheet(78/155 Pages) WOLFSON

78 / 155 page

WM8959

Pre-Production

PP, May 2008, Rev 3.1

MICBIAS CURRENT AND ACCESSORY DETECT

A MICBIAS current detect function is provided for accessory detection. When a microphone current

is detected (e.g. when a headset is inserted), an interrupt event can be generated and the

microphone status read back via the control interface.

The MICBIAS current detect threshold is programmable. A short-circuit current detection is also

available, with a programmable threshold. These functions are enabled by register bit MCD; the

thresholds are programmable via register fields MCDTHR and MCDSCTR as shown in Table 41.

The polarity of the current detect GPIO signals may be controlled by register bits MICDET_POL and

MICSHRT_POL. Note that these polarity inversion bits apply to the Interrupt register behaviour only;

they do not affect the direct GPIO output of the Current Detect functions. The respective interrupt

events may be masked or enabled by register bits MICDET_IRQ_ENA and MICSHRT_IRQ_ENA.

The MICBIAS current threshold status bits contained in the IRQ Register (R18) may be read at any

time or else in response to an Interrupt event. See Table 47 for more details of the Interrupt function.

If direct output of the MICBIAS current detect function is required to the external pins of the WM8959,

the following register settings are required:

•

GPIO1_ENA = 1 (only required if using GPIO1)

•

AIF_SEL = 0 (only required if using GPIO3, GPIO4 or GPIO5)

•

AIF_TRIS = 0

•

GPIOn_SEL = 1000 for the selected GPIO MICBIAS Current Detect output pin

•

GPIOn_SEL = 1001 for the selected GPIO MICBIAS Short Circuit Detect output pin

•

GPIOn_PU = 0 for the selected GPIO MICBIAS output pin or pins

•

GPIOn_PD = 0 for the selected GPIO MICBIAS output pin or pins

The register fields used to configure the MICBIAS Current Detect function are described in Table 41.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

7:6

MCDSCTH

[1:0]

00b

MICBIAS Short Circuit Detect Threshold

00 = 600uA

01 = 1200uA

10 = 1800uA

11 = 2400uA

These values are for AVDD=3.3V and

scale proportionally with AVDD.

5:3

MCDTHR

[2:0]

000b

MICBIAS Current Detect Threshold

000 = 200uA

001 = 350uA

010 = 500uA

011 = 650uA

100 = 800uA

101 = 950uA

110 = 1100uA

111 = 1250uA

These values are for AVDD=3.3V and

scale proportionally with AVDD.

R58 (3Ah)

MCD

MICBIAS Current and Short Circuit

Detect Enable

0 = disabled

1 = enabled

R23 (17h)

MICSHRT_POL

(rw)

MICBIAS short circuit detect polarity

0 = Non-inverted

1 = Inverted

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