PCM5xxx

Audio DAC

Linear

Regulator

3.3V

10 F

GND

GND

SMPS

6V

GND

XSMT

110V / 220V

MCU GPIO

“mute” signal

PCM5100A, PCM5101A, PCM5102A

PCM5100A-Q1, PCM5101A-Q1, PCM5102A-Q1

SLAS859C – MAY 2012 – REVISED MAY 2015

www.ti.com

Recommended Powerdown Sequence (continued)

Figure 38. Using the XSMT Pin

11.3 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 39 )

•

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

voltage 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 40.

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 PCM510xA 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.

30

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