LM4930 datasheet(32/33 Pages) NSC

32 / 33 page

Application Information (Continued)

Standby Mode (0001b)

The LM4930 is powered down, but outputs are still biased at

one half AVDD. This comes at some current cost, but pro-

vides a much faster turn-on time with zero "click and pop"

transients on the headphone out. Standby mode can be

toggled into and out of rapidly and is ideal for saving power

whenever continuous audio is not a requirement. All other

part functions are suspended unless PCM_ALWAYS_ON (bit

10 in BASICCONFIG register) is enabled, in which case

PCM_CLK and PCM_SYNC will continue to function.

Mono Speaker Mode (0010b)

Part is active. All analog outputs are biased. Audio from the

voiceband codec is routed to the mono speaker out. Stereo

headphone out is silent.

Headphone Call Mode (0011b)

Part is active. All analog outputs are biased. Audio from

voiceband codec is routed to the stereo headphones. Both

left and right channels are the same. Mono speaker out is

silent.

Conference Call Mode (0100b)

Part is active. All analog outputs are biased. Audio from the

voiceband codec is routed to the mono speaker out and to

the stereo headphones.

L+R Mixed to Mono Speaker (0101b)

Part is active. All analog outputs are biased. Full-range audio

from the 16bit/48kHz audio DAC is mixed together and

routed to the mono speaker out. Stereo headphones are

silent.

Headphone Stereo Audio (0110b)

Part is active. All analog outputs are biased. Full-range audio

from the 16bit/48kHz audio DAC is sent to the stereo head-

phone jack. Each channel is heard discretely. The mono

speaker is silent.

L+R Mixed to Mono Speaker + Stereo Headphone

Audio (0111b)

Part is active. All analog outputs are biased. Full-range audio

from the 16bit/48kHz audio DAC is sent discretely to the

stereo headphone jack and also mixed together and sent to

the mono speaker out.

Mixed Mode (1000b)

Part is active. All analog outputs are biased. This provides

one channel (the left channel) of full range audio to the mono

speaker out. Audio from the voiceband codec is then sent to

the stereo headphones, the same on each channel.

Mixed Mode (1001b)

Part is active. All analog outputs are biased. Mixed voice-

band and full-range audio (left channel only) is sent to the

mono speaker out. Audio from the voiceband codec only is

sent to the stereo headphones, the same on each channel.

Mixed Mode (1010b)

Part is active. All analog outputs are biased. Audio from the

voiceband codec is sent to the mono speaker out. The left

channel only of the full range audio is then sent to both the

left and right channels of the stereo headphone out.

REGISTERS

The LM4930 starts on power-up with all registers cleared in

Powerdown mode. Powerdown mode is the recommended

time to make setup changes to the digital interfaces (PCM

bus, I2S bus). Although the configuration registers can be

changed in any mode, changes made during Standby or

Powerdown prevent unwanted audio artifacts that may occur

during rapid mode changes with the outputs active. The

LM4930 also features a soft reset. This reset is enabled by

setting bit 4 of the BASICCONFIG register.

The VOICETESTCONFIG register is used to set various

configuration parameters on the voiceband and full-range

audio codecs. SIDETONE_ATTEN (bits 4:1) refers to the

level of signal from the MIC input that is fed back into the

analog audio output path (commonly used in headphone

applications and killed in hands-free applications). Setting

the AUTOSIDE bit (bit 5) automatically mutes the sidetone in

voice over mono speaker modes so feedback isn’t an issue.

Quick mute functions are also located in this register, with

bits 13:15 muting the mono speaker amp, the headphone

amp, and the mic preamp respectively.

This register also has a CLOCK_DIV bit (bit 6) which, if set,

allows for the use of a 24.576MHz clock instead of the

default 12.288MHz.

The GAINCONFIG register is used to control the gain of the

mono speaker amp , the headphone amp, and the mic

preamp. This allows flexible mono speaker gains from

-34.5dB to +12dB in 1.5dB steps, headphone amp gains of

-46.5dB to 0dB in 1.5dB steps, and mic preamp gains of

17dB to 47dB in 2dB steps. Gain levels may be modified in

any mode, but may wait for a zero cross detect in the DAC to

eliminate volume control artifacts. This wait for zero cross

may be disabled by setting the ZXD_DISABLE bit (bit 7) in

the VOICETESTCONFIG register to allow immediate

changes.

ANALOG INPUTS AND OUTPUTS

The LM4930 features an analog mono BTL output for con-

nection to an 8

Ω external speaker. This output can provide

up to 1W of power into an 8

Ω load with a 5V analog supply.

A single-ended stereo headphone output is also featured,

providing up to 30mW of power per channel into 32

Ω with a

5V analog supply.

A Headphone Sense output is provided on J6 for connection

to an external controller. This pin goes high when a hea-

phone is present (when used as shown in Figure 5) and will

function in all modes independent of other operations the

LM4930 may be currently processing.

The MIC Jack input (J3) provides for a low level analog input.

Pin 3 provides the power to the MIC and the positive input of

the LM4930. Gain for the MIC preamp is set in the GAIN-

CONFIG register.

LM4930 Datasheet(PDF) 32 Page - National Semiconductor (TI)

LM4930 Datasheet(HTML) 32 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

Datasheet Download

Link URL