LM4930LQBD National Semiconductor, LM4930LQBD Datasheet - Page 32

• Manufacturer Part Number: LM4930LQBD
• Description: BOARD EVALUATION LM4930LQ
• Manufacturer: National Semiconductor
• Series: Boomer®r

Specifications of LM4930LQBD

• Amplifier Type: Class AB
• Output Type: 1-Channel (Mono) with Stereo Headphones
• Max Output Power X Channels @ Load: 1W x 1 @ 8 Ohm; 27mW x 2 @ 32 Ohm
• Voltage - Supply: 2.6 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Board Type: Fully Populated
• Utilized Ic / Part: LM4930
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Application Information
MIC Jack (J3)
This jack is for connection to an external microphone like the
kind typically found in mobile phones. Pin 1 is GND, pin 2 is
the negative input pin, and pin 3 is the positive pin, with
phantom voltage supplied by MIC_BIAS on the LM4930.
IRQ (J4)
This pin provides simple status updates from the LM4930 to
an external microcontroller if desired. IRQ is logic high when
the LM4930 is in a stable state and changes to low when
changing modes. This can also be useful for simple
software/driver development to monitor mode changes, or as
a simple debugging tool.
BASIC OPERATION
The LM4930 is a highly integrated audio subsystem with
many different operating modes available. These modes
may be controlled in the BASICCONFIG register in bits 3:0.
These mode settings are shown in the BASICCONFIG reg-
ister table and are described here below:
Powerdown Mode (0000b)
Part is powered down, analog outputs are not biased. This is
a minimum current mode. All part features are shut down.
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.
(Continued)
32
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 8Ω external speaker. This output can provide
up to 1W of power into an 8Ω load with a 5V analog supply.