TS2411

The application circuit illustrates the use of the TS2411 devices in typical telephone or extension tone ringer  application. 

The AC ringer signal voltage appears across the TIP and RING inputs of the circuit and is attenuated by capacitorC1  and resistor R1.    C1 also provides isolation from DC voltages (48V) on the exchange line.  After full wave rectification by the bridge diode, the waveform is filtered by capacitor C4 to provide a DC supply  for the tone ringer chip. As this voltage exceeds the initiation voltage (VSI), oscillation starts.  With the components shown, the ouptut frequency chops between 512(fh1) and 640Hz(fh2) at a 10Hz(fL) rate.

The loudspeaker load is coupled through a 1300W to 8W transformer.

The output coupling capacitor C5 is required with transformer coupled loads.  When driving a piezo-ceramic transducer type load, the coupling C5 and transformer (1300W:8W) are not required. However, a current limiting resistor is required.

The low frequency oscillator oscillates at a rate (fL) controlled by an external resistor (R2) and capacitor (C2).

The frequency can be determined using the relation fL=1/1.289R2*C2. The high frequency oscillates at a fH1, fH2 controlled by an external resistor (R3) and capacitor (C3). The frequency can be determined using the relationH1=1/1.504R3*C3, fH2=1/1.203R3*C3. 
 
Pin 2 allows connection of an external resistor RSL, which is used to program the solpe of the supply current vs  supply voltage characteristics (see Fig2), and hence the supply current up to the initiation voltage ( VSI ). This  initiation voltage remains constant independent of RSL.

The supply current drawn prior to triggering varies inversely with RSL, decreasing for increasing value of  resistance. Thus, increasing the value of RSL will decrease the amount of AC ringing current required to trigger the  device. As such, longer sucribser loops are possible since less voltage is dropped per unit length of loop wire due to  the lower current level. RSL can also be used to compensated for smaller AC couplin capacitors (C5 on Fig 3)  (higher impedance) to the line which can be used to alter the ringer equivalence number of a tone ringer circuit.  The graph in Fig2 illustrates the variation of supply current with supply voltage. Three curves are drawn to show  the variation of initiation current with RSL. Curve B( RSL=6.8KW) shows the I-V characteristic for the TS2411 tone  ringer.

Curve A is a plot with RSL<6.8KW and shows an increase in the current drawn up to the initiation voltage VSI. The  I-V characteristic after initiation remains unchanged. Curve C illustrates the effect of increasing RSL above 6.8KW  initiation current decreases but again current after triggering is unchanged.