TLV320AIC21 datasheet(45/56 Pages) TI1

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Layout and Grounding Guidelines for TLV320AIC2x

TLV320AIC2x-to-DSP Interface

FSX

FSR

CLKX

CLKR

TMS320C54X

TMS320C6X

SCLK

TLV320AIC20

MCLK

DIN

DOUT

M/S

IOVDD

From

Oscillator

Hybrid Circuit External Connections

TLV320AIC20, TLV320AIC21

TLV320AIC24, TLV320AIC25

TLV320AIC20K, TLV320AIC24K

SLAS363D – MARCH 2002 – REVISED APRIL 2005

TLV320AIC2x has a built-in analog antialias filter, which provides rejection to external noise at high frequencies

that may couple into the device. Digital filters with high out-of-band attenuation also reject the external noise. If

the differential inputs are used for the ADC channel, then the noise in the common-mode signal is also rejected

by the high CMRR of TLV320AIC2x. Using external common-mode for microphone inputs also helps reject the

external noise. However to extract the best performance from TLV320AIC2x, care must be taken in board design

and layout to avoid coupling of external noise into the device.

TLV320AIC2x supports clock frequencies as high as 100 MHz. To avoid coupling of fast switching digital signals

to analog signals, the digital and analog sections should be separated on the board. In TLV320AIC2x the digital

and analog pins are kept separated to aid such a board layout. A separate analog ground plane must be used for

the analog section of the board. The analog and digital ground planes should be shorted at only one place as

close to TLV320AIC2x as possible. No digital trace should run under TLV320AIC2x to avoid coupling of external

digital noise into the device. It is suggested to have the analog ground plane running below the TLV320AIC2x.

The power-supplies must be decoupled close to the supply pins, preferably, with 0.1 µF ceramic capacitor and

10 µF tantalum capacitor following. The ground pin must be connected to the ground plane as close as possible

to the TLV320AIC2x, so as to minimize any inductance in the path. Since the MCLK is expected to be a very

high frequency signal, it is advisable to shield it with digital ground. For best performance of ADC in differential

input mode, the differential signals must be routed close to each other in similar fashion, so that the noise

coupling on both the signals is the same and can be rejected by the device.

Extra care has to be taken for the speaker driver outputs, as any trace resistance can cause a reduction in the

maximum swing that can be seen at the speaker.

The TLV320AIC2x interfaces gluelessly to the McBSP port of a C54x or C6x TI DSP. Figure 34 shows a single

TLV320AIC2x connected to a C54x or C6x TI DSP.

Figure 34. TLV320AIC2xs Interface to McBSP Port of C54x or C6x DSP

The TLV320AIC2x connected to the telephone line using the LINEI and LINEO hybrid circuit is shown in

Figure 35.

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