DIGITAL MICROPHONE CONNECTIVITY
ANALOG FULLY DIFFERENTIAL LINE OUTPUT DRIVERS
TLV320AIC34
SLAS538A – OCTOBER 2007 – REVISED NOVEMBER 2007
The TLV320AIC34 includes support for connection of digital microphones to the device by routing the digital
signal directly into the ADC digital decimation filter, where it is filtered, downsampled, and provided to the host
processor over the audio data serial bus.
When digital microphone mode is enabled, the TLV320AIC34 provides an oversampling clock output on
GPIO1_x for use by the digital microphone to transmit its data, which is applied to the device on GPIO2_x. The
TLV320AIC34 includes the capability to latch the data on either the rising, falling, or both edges of this supplied
clock, enabling support for stereo digital microphones. Digital microphone operation is configured using page 0,
registers 98 – 99 of each partition. The the oversampling ratio is configured using page 0, register 8, and the
digital microphone and on-chip analog microphone can be selected independently for each ADC channel using
page 0, register 107. For more details on digital microphone support, see the Using the Digital Microphone
Function on TLV320AIC33 With AIC33EVM/USB-MODEVM System application report (SLAA275 ).
The TLV320AIC34 has two fully differential line output drivers, three in each partition, with each driver capable of
driving a 10-k Ω differential load. The output stage design leading to the fully differential line output drivers for one
partition is shown in Figure 33 and Figure 34 . This design includes extensive capability to adjust signal levels
independently before any mixing occurs, beyond that already provided by the PGA gain and the DAC digital
volume control.
The LINE1LP_x and LINE1LM_x signals refer to the signals that travel through the analog input bypass path to
the output stage. The PGA_L/R signals refer to the outputs of the ADC PGA stages that are similarly passed
around the ADC to the output stage. Note that because both left- and right-channel signals of each partition are
routed to all output drivers of that partition, a mono mix of any of the stereo signals can easily be obtained by
setting the volume controls of both left- and right-channel signals to – 6 dB and mixing them. Undesired signals
can also be disconnected from the mix through register control.
Copyright © 2007, Texas Instruments Incorporated Submit Documentation Feedback 45
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