WM8993 datasheet(37/229 Pages) WOLFSON

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Production Data

WM8993

PD, November 2010, Rev 4.0

Note that the maximum source current capability for MICBIAS1 and MICBIAS2 is 2.4mA each. The

external biasing resistance must be large enough to limit each MICBIAS current to 2.4mA across the

full microphone impedance range.

An external capacitor is required on MICBIAS1 and MICBIAS2 in order to ensure accuracy and

stability of each regulator. The recommended capacitance is 4.7

μF in each case. See

“Recommended External Components” for further details.

Note that, if the MICBIAS1 or MICBIAS2 regulator is not enabled, then no external capacitor is

required on the respective MICBIAS pin.

MICROPHONE CURRENT DETECT

A MICBIAS current detect function allows detection of accessories such as headset microphones.

When the MICBIAS load current exceeds one of two programmable thresholds, (e.g. short circuit

current or normal operating current), an interrupt or GPIO output can be generated. The current

detection circuit is enabled by the JD_ENA bit; the current thresholds are selected by the JD_THR

and JD_SCTHR register fields as described in Table 66. See “General Purpose Input/Output” for a

full description of these fields.

LINE AND VOICE CODEC INPUTS

All eight analogue input pins may be used as line inputs. Each line input has different signal path

options, providing flexibility, high performance and low power consumption for many different usage

modes.

IN1LN and IN1RN can operate as single-ended line inputs to the input PGAs IN1L and IN1R

respectively. These inputs provide a high gain path if required for low input signal levels.

IN2LN and IN2RN can operate as single-ended line inputs to the input PGAs IN2L and IN2R

respectively, providing further high gain signal paths. These pins can also be connected to either of

the output mixers MIXOUTL and MIXOUTR.

IN1LP and IN1RP can operate as single-ended line inputs to the input mixers MIXINL and MIXINR, or

to the speaker mixers SPKMIXL and SPKMIXR. These signal paths enable power consumption to be

reduced, by allowing the input PGAs and other circuits to be disabled if not required.

IN2LP/VRXN and IN2RP/VRXP can operate in three different ways:



Mono differential ’RXVOICE’ input (e.g. from an external voice CODEC) to the input mixers

MIXINL and MIXINR.



Single-ended line inputs to either of the output mixers MIXOUTL and MIXOUTR.



Ultra-low power mono differential ‘Direct Voice’ input (e.g. from an external voice CODEC)

to the ear speaker driver on HPOUT2, or to either of the speaker drivers on SPKOUTL and

SPKOUTR.

Signal path configuration to the input PGAs and input mixers is detailed later in this section. Signal

path configuration to the output mixers and speaker mixers is described in “Output Signal Path”.

The line input and voice CODEC input configurations are illustrated in Figure 10 through to Figure 13.

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