TCM29C13 Datasheet, PDF (18/25 Pages) Texas Instruments – COMBINED SINGLE-CHIP PCM CODEC AND FILTER

TCM29C13, TCM29C14, TCM29C16, TCM29C17,
TCM129C13, TCM129C14, TCM129C16, TCM129C17
COMBINED SINGLE-CHIP PCM CODEC AND FILTER
SCTS011H – APRIL 1986 – REVISED JULY 1996
PRINCIPLES OF OPERATION
VCC
DGND
VBB
Figure 7. Diode Configuration for Latch-Up Protection Circuitry
internal sequencing
On the transmit channel, digital outputs PCM OUT and TSX are held in the high-impedance state for
approximately four frames (500 µs) after power up or application of V_{BB or} V_CC. After this delay, PCM OUT, TSX,
and signaling are functional and occur in the proper time slot. The analog circuits on the transmit side require
approximately 60 ms to reach their equilibrium value due to the autozero circuit settling time. Therefore, valid
digital information, such as on/off hook detection, is available almost immediately while analog information is
available after some delay.
On the receive channel, the digital output SIGR is also held low for a maximum of four frames after power up
or application of V_BB or V_CC. SIGR remains low until it is updated by a signaling frame.
To further enhance system reliability, PCM OUT and TSX are placed in the high-impedance state approximately
20 µs after an interruption of CLKX. SIGR is held low approximately 20 µs after an interruption of CLKR. These
interruptions could possibly occur with some kind of fault condition.
power-down and standby operations
To minimize power consumption, a power-down mode and three standby modes are provided.
For power down, an external low signal is applied to PDN. In the absence of a signal, PDN is internally pulled
up to a high logic level and the device remains active. In the power-down mode, the average power consumption
is reduced to 5 mW.
Three standby modes give the user the options of placing the entire device on standby, placing only the transmit
channel on standby, or placing only the receive channel on standby. To place the entire device on standby, both
FSX and FSR are held low. For transmit-only operation (receive channel on standby), FSX is high and FSR is
held low. For receive-only operation (transmit section on standby), FSR is high and FSX is held low. When the
entire device is in standby mode, power consumption is reduced to an average of 3 mW. See Table 1 for
power-down and standby procedures.
Table 1. Power-Down and Standby Procedures
DEVICE STATUS
PROCEDURE
Power down
PDN low
Entire device on standby ^{FSX and FSR are low}
Only transmit on standby ^{FSX is low, FSR is high}
Only receive on standby FSR is low, FSX is high
TYPICAL POWER
CONSUMPTION
3 mW
3 mW
40 mW
30 mW
DIGITAL OUTPUT STATUS
TSX and PCM OUT are in the high-impedance state; SIGR
goes low within 10 µs.
TSX and PCM OUT are in the high-impedance state; SIGR
goes low within 300 ms.
TSX and PCM OUT are placed in the high-impedance state
within 300 ms.
SIGR is placed in the high-impedance state within 300 ms.
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