WM8959 Wolfson Microelectronics Ltd., WM8959 Datasheet - Page 78

• Manufacturer Part Number: WM8959
• Description: Mobile Multimedia DAC with Dual-mode Class AB/D Speaker Driver
• Manufacturer: Wolfson Microelectronics Ltd.

WM8959
w
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:
The register fields used to configure the MICBIAS Current Detect function are described in Table 41.
R58 (3Ah)
R23 (17h)
REGISTER
ADDRESS
•
•
•
•
•
•
•
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
7:6
5:3
2
10
BIT
MCDSCTH
[1:0]
MCDTHR
[2:0]
MCD
MICSHRT_POL
(rw)
LABEL
DEFAULT
000b
00b
0b
0b
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.
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.
MICBIAS Current and Short Circuit
Detect Enable
0 = disabled
1 = enabled
MICBIAS short circuit detect polarity
0 = Non-inverted
1 = Inverted
DESCRIPTION
PP, May 2008, Rev 3.1
Pre-Production
78