
TCM37C14A, TCM37C15A
PCMCOMBO WITH PROGRAMMABLE GAIN CONTROL
SLWS018B – JUNE 1996 – REVISED MAY 1998
15
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
miscellaneous functions (continued)
gain adjustment
If gain is used on the receive side, the input PCM data levels must be properly limited to prevent saturation of
the output amplifier. Refer to the gain and dynamic range table in the electrical characteristics section.
The gain of the transmit and receive amplifiers is set by external resistors connected to the device as shown
in Figure 6 and can be adjusted using internal switching elements as shown in Table 1.
_
+
PWRO+
RIN
RS1
RS2
GSR
From Buffer
AGND
RSF
_
+
GSX
ANLGIN
TS1
TS2
AGND
RTF
RSIN
RSA
RSB
S0
S1
S0
S1
Analog Input
RTIN
RTA
RTB
Receive Gain Control Circuitry
(Gain Configuration)
Transmit Gain Control Circuitry
(Gain Configuration)
Analog Output
Figure 6. Gain Control Circuitry
Table 1. Logic Table for Programmable Gain Control
CONTROL
TERMINALS
INTERNAL SWITCH POSITION
TRANSFER FUNCTION
(GAIN)
GS0
GS1
RS1
RS2
TS1
TS2
RECEIVE
TRANSMIT
Low
Low
Power Down
Low
Hi
Open
Open
Open
Open
– RSF/RSIN
– RTF/RTIN
Hi
Low
Closed
Open
Closed
Open
– RSF/RSIN || RSA
– RTF/RTIN || RTA
Hi
Hi
Open
Closed
Open
Closed
– RSF/RSIN || RSB
– RTF/RTIN || RTB