W681512
of this output amplifier can be achieved. If the transmit power amplifier is not in use, it can be powered
down by connecting PAI to V
DD
.
7.3. P
OWER
M
ANAGEMENT
7.3.1. Analog and Digital Supply
The power supply for the analog and digital parts of the W681512 must be 5V +/- 10%. This supply
voltage is connected to the V
DD
pin. The V
DD
pin needs to be decoupled to ground through a 0.1
μF
ceramic capacitor.
7.3.2. Analog Ground Reference Voltage Output
The analog ground reference voltage is available for external reference at the V
AG
pin. This voltage
needs to be decoupled to V
SS
through a 0.01
μF
to a 0.1
μF
ceramic capacitor.
7.4. PCM I
NTERFACE
The PCM interface is controlled by pins BCLKR, FSR, BCLKT & FST. The input data is received
through the PCMR pin and the output data is transmitted through the PCMT pin. The modes of
operation of the interface are shown in Table 7.3.
BCLKR
64 kHz to 4.096 MHz
V
SS
V
SS
V
DD
V
DD
FSR
8 kHz
V
SS
V
DD
V
SS
V
DD
Interface Mode
Long or Short Frame Sync
ISDN GCI with active channel B1
ISDN GCI with active channel B2
ISDN IDL with active channel B1
ISDN IDL with active channel B2
Table 7.3 PCM Interface mode selections
7.4.1. Long Frame Sync
The Long Frame Sync or Short Frame Sync interface mode can be selected by connecting the
BCLKR or BCLKT pin to a 64 kHz to 4.096 MHz clock and connecting the FSR or FST pin to the 8
kHz frame sync. The device synchronizes the data word for the PCM interface and the CODEC
sample rate on the positive edge of the Frame Sync signal. It recognizes a Long Frame Sync when
the FST pin is held HIGH for two consecutive falling edges of the bit-clock at the BCLKT pin. The
length of the Frame Sync pulse can vary from frame to frame, as long as the positive frame sync edge
occurs every 125
μsec.
During data transmission in the Long Frame Sync mode, the transmit data pin
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