WM8994 datasheet(151/359 Pages) WOLFSON

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Production Data

WM8994

PD, April 2012, Rev 4.4

151

ACCESSORY DETECTION (MICBIAS CURRENT DETECTION)

Current detection is provided on each of the microphone bias sources MICBIAS1 and MICBIAS2.

These can be configured to detect when an external accessory (such as a microphone) has been

connected. The output voltage of each of the microphone bias sources is selectable. Two current

detection threshold levels can be set; these thresholds are applicable to both microphone bias

sources.

The logic signals from the current detect circuits may be output directly on any GPIO pin by setting

the respective GPIO registers as described in “GPIO Control”. De-bounce can be applied to these

signals using the register bits described in Table 83.

The current detection circuits are inputs to the Interrupt control circuit, after the selectable de-bounce.

An interrupt event is triggered on the rising and falling edges of the current detect signals. The

associated interrupt bits are latched once set; they can be polled at any time or used to control the

IRQ signal. See “Interrupts” for more details of the Interrupt event handling.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1 (0001h)

Power

Management

(1)

MICB2_ENA

Microphone Bias 2 Enable

0 = Disabled

1 = Enabled

MICB1_ENA

Microphone Bias 1 Enable

0 = Disabled

1 = Enabled

R58 (003Ah)

MICBIAS

7:6

MICD_SCT

HR [1:0]

MICBIAS Short Circuit Current threshold

00 = 300uA

01 = 600uA

10 = 1200uA

11 = 2400uA

These values are for AVDD1=3.0V and scale

proportionally with AVDD1.

5:3

MICD_THR

[2:0]

000

MICBIAS Current Detect threshold

00X = 150uA

01X = 300uA

10X = 600uA

11X = 1200uA

These values are for AVDD1=3.0V and scale

proportionally with AVDD1.

MICD_ENA

MICBIAS Current Detect / Short Circuit

Threshold enable

0 = Disabled

1 = Enabled

MICB2_LVL

Microphone Bias 2 Voltage Control

0 = 0.9 * AVDD1

1 = 0.65 * AVDD1

MICB1_LVL

Microphone Bias 1 Voltage Control

0 = 0.9 * AVDD1

1 = 0.65 * AVDD1

R1864

(0748h)

IRQ

Debounce

MIC2_SHRT

_DB

MICBIAS2 Short Circuit de-bounce

0 = Disabled

1 = Enabled

MIC2_DET_

MICBIAS2 Current Detect de-bounce

0 = Disabled

1 = Enabled

MIC1_SHRT

_DB

MICBIAS1 Short Circuit de-bounce

0 = Disabled

1 = Enabled

MIC1_DET_

MICBIAS1 Current Detect de-bounce

0 = Disabled

1 = Enabled

Table 83 MICBIAS Enable and GPIO/Interrupt Control

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