PCM1681PWPR datasheet(21/44 Pages) TI1

21 / 44 page

PCM1681, PCM1681-Q1

www.ti.com

SLES211C – FEBRUARY 2008 – REVISED JULY 2015

In serial control mode, actual mode control is performed by a register write (and read) through the I2C or SPI

compatible serial control port. In parallel H/W control mode, the specific four functions are controlled directly

through high-level/low-level control of five specific pins (see Parallel Hardware Control section), and the zero-flag

function of ZR1 is not applicable.

8.3.8.1 Parallel Hardware Control

Four functions are controlled by five pins, MSEL, FMT0, FMT1, DEMP, and MUTE in parallel hardware control

mode.

MSEL TERMINATION(1)

DESCRIPTION

Pull-down resistor to DGND

Narrow oversampling mode

Pull-up resistor to VDD

Wide oversampling mode

(1)

The MSEL termination controls the oversampling mode for all eight channels.

FMT1(1)

FMT0(1)

DESCRIPTION

LOW

24-bits right-justified format

LOW

HIGH

16 to 24-bits I2S format

HIGH

LOW

16 to 24-bits left-justified format

HIGH

24-bits I2S mode TDM format

(1)

The FMT0 and FMT1 pins control the audio interface format for all eight channels.

DEMP(1)

DESCRIPTION

LOW

De-emphasis off

HIGH

44.1-kHz De-emphasis on

(1)

The DEMP pin controls the 44.1-kHz digital de-emphasis function of all eight channels.

MUTE(1)

DESCRIPTION

LOW

Mute off (mute disable)

HIGH

Mute on (mute enable)

(1)

The MUTE pin controls all 8 channel outputs at the same time.

8.3.8.2 SPI Control Interface

The SPI control interface of the PCM1681 and PCM1681-Q1 is a 3-wire synchronous serial port that operates

asynchronously to the serial audio interface. The SPI control interface is used to program the on-chip mode

registers. The control interface includes MD (pin 4), MC (pin 3), and MS (pin 2). MD is the serial data input, used

to program the mode registers. MC is the control port for the serial bit clock, used to shift in the serial data, and

MS is the control port for mode control select, which is used to enable the mode control. The SPI control

interface is available when MSEL (pin 14) is tied with VDD and after power-on reset completion.

8.3.8.3 Analog Outputs

The PCM1681 and PCM1681-Q1 include eight independent output channels, VOUT1 through VOUT8. These are

unbalanced outputs, each capable of driving 3.75 VPP typical into a 5-kΩ ac load with VCC = 5 V. The internal

output amplifiers for VOUT1 through VOUT8 are biased to the dc common voltage, equal to 0.486 VCC.

The output amplifiers include an RC continuous-time filter, which helps to reduce the out-of-band noise energy

present at the DAC outputs due to the noise-shaping characteristics of the PCM1681 and PCM1681-Q1

ΔΣ

DACs. The frequency response of this filter is shown in Figure 12. By itself, this filter is not enough to attenuate

the out-of-band noise to an acceptable level for most applications. An external low-pass filter is required to

provide sufficient out-of-band noise rejection. Further discussion of DAC post-filter circuits is provided in the

Application and Implementation section of this data sheet.

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