PCM5121 datasheet(62/121 Pages) TI2

62 / 121 page

PCM5xxx

Audio DAC

Linear

Regulator

3.3V

10 F

GND

SMPS

GND

XSMT

110V / 220V

MCU GPIO

“mute” signal

PCM5121, PCM5122

SLAS763C – AUGUST 2012 – REVISED OCTOBER 2018

www.ti.com

Product Folder Links: PCM5121 PCM5122

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Recommended Powerdown Sequence (continued)

Figure 80. Using the XSMT Pin

10.3 External Power Sense Undervoltage Protection Mode

NOTE

External Power Sense Undervoltage Protection Mode is supported only when

DVDD = 3.3 V.

The XSMT pin can also be used to monitor a system voltage, such as the 24-VDC LCD TV backlight, or 12-VDC

system supply using a voltage divider created with two resistors. (See Figure 81.)

•

If the XSMT pin makes a transition from 1 to 0 over 6 ms or more, the device switches into external

undervoltage protection mode. This mode uses two trigger levels:

–

When the XSMT pin level reaches 2 V, soft mute process begins.

–

When the XSMT pin level reaches 1.2 V, analog mute engages, regardless of digital audio level, and

analog shutdown begins. (DAC and related circuitry powers down).

If XSMT is moved from 1 to 0 in 20 ns or less, then the device will interpret it as a digital controlled request to

mute. It will perform a soft mute, then move to standby.

A timing diagram to show this is shown in Figure 82.

NOTE

The XSMT input pin voltage range is from –0.3 V to DVDD + 0.3 V. The ratio of external

resistors must produce a voltage within this input range. Any increase in power supply

(such as power supply positive noise or ripple) can pull the XSMT pin higher than DVDD +

0.3 V.

For example, if the PCM512x is monitoring a 12-V input, and dividing the voltage by 4, then the voltage at XSMT

during ideal power supply conditions is 3.3 V. A voltage spike higher than 14.4 V causes a voltage greater than

3.6 V (DVDD + 0.3) on the XSMT pin, potentially damaging the device.

Providing the divider is set appropriately, any DC voltage can be monitored.

PCM5121 Datasheet(PDF) 62 Page - Texas Instruments

PCM5121 Datasheet(HTML) 62 Page - Texas Instruments

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