tp3076 National Semiconductor Corporation, tp3076 Datasheet - Page 7

• Manufacturer Part Number: tp3076
• Description: Combo Ii Programmable Pcm Codec/filter For Isdn And Digital Phone Applications
• Manufacturer: National Semiconductor Corporation

Programmable Functions
Note 8: Analog signal path is cut off, but D
codes representing idle noise.
RECEIVE GAIN INSTRUCTION BYTE 2
The receive gain can be programmed in 0.1 dB steps by
writing to the Receive Gain Register as defined in Table 1
and Table 8. Note the following restrictions on output drive
capability:
1. 0 dBm0 levels ≤ 1.96 Vrms at VF
2. 0 dBm0 levels ≤ 1.85 Vrms at VF
3. 0 dBm0 levels ≤ 1.71 Vrms at VF
To calculate the binary code for byte 2 of this instruction for
any desired output 0 dBm0 level in Vrms, take the nearest
integer to the decimal number given by:
and convert to the binary equivalent. Some examples are
given in Table 8. A complete tabulation is given in Appendix I
or AN-614.
a load of ≥ 15 kΩ to GND; Receive Gain set to 0 dB (gain
register set to all ones).
a load of ≥ 600Ω to GND; Receive Gain set to 0.5 dB.
a load of ≥ 300 Ω to GND. Receive Gain set to −1.2 dB.
7 6 5 4 3 2 1 0
1 1 1 1 1 1 1 1
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
TABLE 8. Byte 2 of Receive Gain Instruction
Bit Number
Bit Number
TABLE 7. Byte 2 of Transmit Gain
Instruction (Continued)
200 x log
10
0 dBm0 Test Level (Vrms)
0 dBm0 Test Level (Vrms)
No Output (Low Z to GND)
(V/0.1043)
X
remains active and will output
R
R
R
at VF
at VF
O may be driven into
O may be driven into
O may be driven into
1.375
0.105
R
X
O
(Continued)
I
7
Applications Information
Figure 1 shows a typical ISDN phone application of the
TP3076 together with a TP3420 ISDN Transceiver “S” Inter-
face Device and HPC16400 High-Performance Microcontrol-
ler with HDLC Controller. The TP3076 device is programmed
over its serial control interface via the HPC16400
MICROWIRE/PLUS
POWER SUPPLIES
While the pins of the TP3076 COMBO II device are well
protected against electrical misuse, it is recommended that
the standard CMOS practice of applying GND to the device
before any other connections are made should always be
followed. In applications where the printed circuit card may
be plugged into a hot socket with power and clocks already
present, an extra long ground pin on the connector should be
used and a Schottky diode connected between V
GND.
To minimize noise sources all ground connections to each
device should meet at a common point as close as possible
to the GND pin in order to prevent the interaction of ground
return currents flowing through a common bus impedance.
Power supply decoupling capacitors of 0.1 µF should be
connected from this common point to V
to the device pins as possible.
Further guidelines on PCB layout techniques are provided in
Application Note AN-614, “COMBO II
CODEC/Filter Family Application Guide”.
7 6 5 4 3 2 1 0
0 0 0 0 0 0 1 0
1 1 1 1 1 1 1 0
1 1 1 1 1 1 1 1
Bit Number
—
™
serial I/O port.
0 dBm0 Test Level (Vrms)
™
at VF
0.107
1.941
1.964
CC
Programmable PCM
—
and V
R
O
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