TCM320AC56 Datasheet, PDF (14/23 Pages) Texas Instruments – VOICE-BAND AUDIO PROCESSORS (VBAP)

TCM320AC56, TCM320AC57
VOICE-BAND AUDIO PROCESSORS (VBAP)
SLWS016A – JUNE 1996 – REVISED APRIL 1997
PRINCIPLES OF OPERATION
Table 1. Power-Down and Standby Procedures
DEVICE STATUS
Power on
Power down
Entire device on standby
mode
Only transmit channel in
standby mode
Only receive channel in
standby mode
† _{X = don’t care}
PROCEDURE
PDN = high,
FSX = pulses,
FSR = pulses
PDN = low,
FSX, FSR = X^†
FSX = low,
FSR = low,
PDN = high
FSX = low,
FSR = pulses,
PDN = high
FSR = low,
FSX = pulses,
PDN = high
TYPICAL POWER
CONSUMPTION
DIGITAL OUTPUT STATUS
40 mW
Digital outputs active but not loaded
13 mW
TSX and DOUT in the high-impedance state
5 mW
TSX and DOUT in the high-impedance state
20 mW
TSX and DOUT in the high-impedance state within five
frames
20 mW
Digital outputs active but not loaded
fixed-data-rate timing
Fixed-data-rate timing is selected by connecting DCLKR to V_CC and uses the master clock (CLK), frame
synchronization clocks (FSX and FSR), and the TSX output. FSX and FSR are inputs that set the sampling
frequency. Data is transmitted on DOUT on the positive transitions of CLK following the rising edge of FSX. Data
is received on DIN on the falling edges of CLK following FSR. A D/A conversion is performed on the received
digital word, and the resulting analog sample is held on an internal sample-and-hold capacitor until transferred
to the receive filter. The data word is eight bits long in the companded mode and 16 bits long in the linear mode.
variable-data-rate timing
Variable-data-rate timing is selected by connecting DCLKR to the receive data clock. In this mode, the master
clock (CLK) controls the switched-capacitor filters, while data transfer into DIN and out of DOUT is controlled
by DCLKR and DCLKX respectively. This allows the data to be transferred in and out of the device at any rate
up to the frequency of the master clock. DCLKR and DCLKX must be synchronous with CLK.
While the FSX input is high, data is transmitted from DOUT on consecutive positive transitions of DCLKX.
Similarly, while the FSR input is high, the data word is received at DIN on consecutive negative transitions of
DCLKR. The transmitted data word at DOUT is repeated in all remaining time slots in the frame as long as
DCLKX is pulsed and FSX is held high. This feature, which allows the data word to be transmitted more than
once per frame, is available only with variable-data-rate timing.
asynchronous operations
To avoid crosstalk problems associated with special interrupt circuits, the design includes separate converters,
filters, and voltage references on the transmit and receive sides to allow completely independent operation of
the two channels. In either timing mode, the master clock, data clock, and time-slot strobe must be synchronized
at the beginning of each frame.
precision voltage references
A precision band-gap reference voltage is generated internally and is used to supply all the references required
for operation of both the transmit and receive channels. The gain in each channel is trimmed during the
manufacturing process. This ensures very accurate, stable gain performance over variations in supply voltage
and device temperature.
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