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SYSTEM CLOCK
tw(SCKH)
tw(SCKL)
2 V
0.8 V
1/256 fS
T000510
System Clock
POWER SUPPLY ON, EXTERNAL RESET, AND POWER DOWN
PCM3052A
SLES160 – NOVEMBER 2005
THEORY OF OPERATION (continued)
The system clock for the PCM3052A must be 256 fS, where fS is the audio sampling rate, 16 kHz to 96 kHz.
Table 1 lists typical system clock frequencies, and
Figure 43 illustrates the system clock timing.
Table 1. Typical System Clock
SAMPLING RATE
SYSTEM CLOCK FREQUENCY – MHz
FREQUENCY (fS) – LRCK
256 fS
16 kHz
4.096
32 kHz
8.192
44.1 kHz
11.2896
48 kHz
12.288
96 kHz
24.576
PARAMETER
MIN
MAX
UNIT
tw(SCKH)
System clock pulse duration, HIGH
16
ns
tw(SCKL)
System clock pulse duration, LOW
16
ns
Figure 43. System Clock Timing
The PCM3052A has both an internal power-on-reset circuit and an external reset circuit. The sequences for both
resets are shown as follows.
Figure 44 is the timing chart of the internal power-on reset. Two power-on-reset circuits are implemented, one
each for for VCC1 and VDD. Initialization (reset) is performed automatically at the time when VCC1 and VDD exceed
3.9 V (typical) and 2.2 V (typical), respectively.
Internal reset is released after 1024 SCKI from power-on-reset release, and the PCM3052A begins normal
operation. VOUTL and VOUTR from the DAC are forced to the VCOM (= 0.5 VCC2) level as VCC2 rises. When
synchronization between SCKI, BCK, and LRCK is maintained, VOUTL and VOUTR go into the fade-in sequence.
Then VOUTL and VOUTR provide outputs corresponding to DIN after t(DACDLY1) = 2100/fS from power-on-reset
release. On the other hand, DOUT from the ADC provides an output corresponding to VINL and VINR after
t(ADCDLY1) = 4500/fS from power-on-reset release. If synchronization is not maintained, the internal reset is not
released, and operation is kept in the power-down mode. After resynchronization, the DAC goes into the fade-in
sequence, and the ADC goes into normal operation after internal initialization.
DOUTS can provide S/PDIF data after the power-on-reset release if the SPDIF bit is HIGH (see serial control
port for mode control section).
Figure 45 shows timing chart for external reset. The PDWN pin (pin 9) initiates external forced reset when PDWN
= LOW, and it provides the power-down mode, which is the lowest power-dissipation state in the PCM3052A.
When PDWN transitions from HIGH to LOW while SCKI, BCK, and LRCK are synchronized, VOUTL and VOUTR
are faded out and forced into VCOM (= 0.5 VCC2) level after tDACDLY1 = 2100/fS. At the same time as the internal
reset becomes LOW, DOUT becomes ZERO, the PCM3052A enters the power-down mode. To return to normal
operation, set PDWN to HIGH. Then the power-on reset sequence,
Figure 44, is performed.
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