TEA1062A Low Voltage Transmission Circuits with Dialer Interface IC

The TEA1062A is an integrated circuit that performs all voice and line interface tasks in fully electronic telephone systems. These gadgets are designed to transition between dialling and speaking via electrical switching. To allow for the usage of several telephone sets linked in parallel, the ICs function at line voltages as low as 1.6 V DC (with decreased performance.

The telephone line provides the power necessary for the IC and its peripheral circuitry. The IC regulates the supply voltage, which is obtained from the line through a dropping resistor. External circuits, such as dialling and control circuits, are likewise powered by the supply voltage VCC. A capacitor between VCC and VEE is used to decouple the supply voltage. A capacitor between REG and VEE decouples the internal voltage regulator. Meanwhile, the exchange supply voltage Vexch, the feeding bridge resistance Rexch, and the DC resistance of the telephone line Rline define the DC current flowing into the set.

A 3.6 k resistor connected between STAB and VEE controls the amount of the circuit’s inbuilt current stabiliser (see Fig.9). The surplus current is shunted to VEE through LN when the line current (Iline) is more than 0.5 mA larger than the total of the IC supply current (ICC) and the current drawn by peripheral circuitry linked to VCC (Ip). Calculate the regulated voltage on the line terminal (VLN) as follows:

VLN = Vref + ISLPE × R9

VLN = Vref + {(Iline − ICC − 0.5 × 10−3 A) − Ip} × R9

Vref is an internally generated temperature compensated reference voltage of 3.7 V and R9 is an external resistor connected between SLPE and VEE.