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1024 System Clock Periods

Required for Initialization

SCKI

Internal

Reset

0V

0V

0V

t

RST

Internal

Reset

Analog

Outputs

Outputs are On

Outputs are Muted

for 1024 SCKI Periods

Outputs are On

Outputs are Muted

Initialization

Period

HI

LO

POWER-DOWN OPERATION

PCM4104-EP

SBAS419 – JUNE 2007

Figure 6. External Reset Timing

Figure 7. Analog Output State for Reset Operations

The PCM4104 can be forced to a power-down state by applying a low level to the RST input for a minimum of

65,536 system clock cycles. In power-down mode, all internal clocks are stopped, and analog outputs are set to

a high-impedance state. The system clock can then be removed to conserve additional power. In the case of

system clock restart when exiting the power-down state, the clock should be restarted prior to a low-to-high

transition of the reset signal at the RST input. The low-to-high transition of the reset signal initiates a reset

sequence, as described in the Reset Operation section of this data sheet.

In Software mode, two additional power-down controls are provided. The PDN12 and PDN34 bits are located in

Control Register 6 and may be used to power-down channel pairs, with PDN12 corresponding to channels 1 and

2, and PDN34 corresponding to channels 3 and 4. This allows the user to conserve power when a channel pair

is not in use. The power-down function is the same as described in the previous paragraph for the

corresponding channel pair. Unlike the power-down function implemented using the RST input, setting a

power-down bit will immediately power down the corresponding channel pair.

When exiting power-down mode, either by forcing the RST input high or by setting the PDN12 or PDN34 bits

low, the analog outputs will transition from the high-impedance state to the mute state, with the output level set

to the bipolar zero voltage. There may be a small transient created by this transition, since internal capacitor

charge can initially force the output to a voltage above or below bipolar zero, or external circuitry can pull the

outputs to some other voltage level. Figure 8 illustrates the state of the analog outputs before, during, and after

a power-down event.

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