The TWL6040 device is an audio coder/decoder (codec) with a high level of integration
providing analog audio codec functions for portable applications, as shown in . The device contains multiple audio analog inputs and outputs, as
well as microphone biases and accessory detection. The device is connected to the
OMAP 4 host processor through a proprietary PDM
interface for audio data communication enabling partitioning with optimized power consumption and
performance. Multichannel audio data is multiplexed to a single wire for downlink (PDML) and uplink
The OMAP4 device provides the TWL6040 device with five PDM audio-input channels
(DL0–DL4). Channels DL0–DL3 are connected to four parallel DAC channels multiplexed to stereo
headphone (HSL, HSR), stereo speaker (HFL, HFR), and earpiece (EAR) or stereo line outputs (AUXL,
The stereo headphone path has a low-power (LP) mode operating from a 32-kHz sleep clock
to enable more than 100 hours of MP3 playback time. Very-high dynamic range of 104 dBA is achieved
when using the system clock input and DAC path high-performance (HP) mode. Class-AB headphone
drivers provide a 1-Vrms capability output and are ground centered for
capless connection to a headphone, thus enabling system size and cost reduction. The earpiece
driver is a differential class-AB driver with 2 Vrms capability to a typical
32-Ω load or 1.4 Vrms to a typical 16-Ω load.
Stereo speaker path has filterless class-D outputs with 1.5-W capability per channel.
Output power maximization supply connections to an external boost is supported. Speaker drivers
also support hearing aid coil loads. For vibrator and haptic feedback support, the TWL6040 has two
PWM channels with independent input signals from DL4 or inter-integrated circuit
Vibrator drivers are differential H-bridge outputs, enabling fast acceleration and
deceleration of vibrator motor. An external driver for a hearing aid coil or a piezo speaker
requiring high voltage can be connected to line outputs.
The TWL6040 supports three differential microphone inputs (MMIC, HMIC, and SMIC) and a
stereo line-input (AFML, AFMR) multiplexed to two parallel ADCs. The PDM output from the ADCs is
transmitted to the OMAP4 processor through UL0 and UL1. AFML, AFMR inputs can also be looped to
analog outputs (LB0, LB1).
Two LDOs provide a voltage of 2.1 V to bias analog microphones (MBIAS and HBIAS). The
maximum output current is 2 mA for each analog bias, allowing up to two microphones on one bias.
Two LDOs provide a voltage of 1.8 V/1.85 V to bias digital microphones (DBIAS1 and DBIAS2). One
bias generator can bias several digital microphones at the same time, with a total maximum output
current of 10 mA.
The TWL6040 has an integrated negative charge pump (NCP) and two LDOs (HS LDO and LS
LDO) for high PSRR. The only external supply needed is 2.1 V, which is available from the 2.1-V
DC-DC of the TWL6030 power-management IC (PMIC) in the OMAP4 system. By powering audio from
low-noise 2.1-V DC-DC of low power consumption, high dynamic range and high output swing at headset
output are achieved. All other supply inputs can be directly connected to battery or system 1.8-V
Two integrated PLLs enable operation from a 12-, 19.2-, 26-, and 38.4-MHz system clock
(MCLK) or, in LP playback mode, from a 32-kHz sleep clock (CLK32K). The frequency plan is based on
a 48-kS/s audio data rate for all channels, and host processor uses sample-rate converters to
interface with different sample rates (for example, 44.1 kHz). In the specific case of low-power
audio playback, the TWL6040 supports the 44.1-kS/s and 48-kS/s rates. Transitions between sample
rates or input clocks are seamless.
Accessory plug and unplug detections are supported (PLUGDET). Some headsets have a
manual switch for submitting send/end signal to the terminal through the microphone input pin. This
feature is supported by a periodic accessory button press detection to minimize current consumption
in sleep mode. Detection cycle properties can be programmed according to system
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