WM8953ECSSLASHRV datasheet(45/100 Pages) WOLFSON

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Production Data

WM8953

PD, January 2009, Rev 4.0

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 24.

Current detect and short circuit detect thresholds are subject to a +/- 30% temperature, supply and

part-to-part variation. This should be factored into any application design.

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 30 for more details of the Interrupt function.

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

WM8953, the following register settings are required:

•

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 24.

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

MICSHRT_POL

(rw)

MICBIAS short circuit detect polarity

0 = Non-inverted

1 = Inverted

R23 (17h)

MICDET_POL

(rw)

MICBIAS current detect polarity

0 = Non-inverted

1 = Inverted

WM8953ECS/RV 数据表(PDF) 45 Page - Wolfson Microelectronics plc

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