DS_S1T2410B01 Datasheet, PDF (5/8 Pages) Samsung semiconductor – bipolar integrated circuit designed as a telephone bell replacement

TONE RINGER
S1T2410B01/B02
APPLICATION INFORMATION
The application circuit illustrates the use of the S1T2410B01/B02 devices in typical telephone or extensive tone
ringer applications.
The AC ringer signal voltage appears across the TIP and RING inputs of the circuit, and is attenuated by capacitor
C₁ and resistor R₁.
(C₁ also provides isolation from DC voltages (48V) on the exchange line).
After full wave rectification by the bridge diode, the wave form is filtered by capacitor C₄ to provide a DC supply for
the tone ringer chip.
When this voltage exceeds the initiation (V_SI), oscillation starts.
With the components shown, the output frequency chops between 512 Hz (f_H1) and 640Hz (f_H2) at a 10Hz (f_L) rate.
The loudspeaker load is coupled through a 1300Ω to 8Ω transformer.
The output coupling capacitor C₅ with transformer coupled loads is required.
When driving a piezo-ceramic transducer type load, the coupling C₅ and transformer (1300Ω :8 Ω) are not required.
However, a current limiting resistor is required.
The low frequency oscillator oscillates at a rate (f_L) controlled by an external resistor (R₂) and capacitor (C₂). The
frequency can be determined using the function f_L = 1/(1.289 R₂ • C₂). The high frequency oscillates at a f_H1, f_H2
controlled by an external resistor (R₃) and capacitor (C₃). The frequency can be determined using the function t_HI
= 1/(1.504 R₃ • C₃). Voltage remains constant independent of R_SL.
Pin 2 of the S1T2410B02 allows connection of an external resistor R_SL, which is used to program the slope of the
supply current vs supply voltage characteristics (see Fig. 2) and hence the supply current up to the initial voltage
(V_SI). This initial voltage remains constant independent of R_SL.
The supply current drawn prior to triggering is inversely proportional with R_SL, decreasing for an increasing value of
resistance.
Thus, increasing the value of R_SL, will decrease the amount of AC ringing current required to trigger the device.
Longer subscriber loops are possible since less voltage is dropped per unit length of loop wire due to the lower
current level. R_SL can also be used to compensate for smaller AC coupling capacitors (C₅ on Fig. 3) (higher
impedance) to the line which is used to alter the ringer equivalence number of a tone ringer circuit.
The graph in Fig. 2 illustrates the variation of supply current with supply voltage of the S1T2410B02. Three curves
are drawn to show the variation of the initiation current with R_SL. Curve B (R_SL = 6.8kΩ) shows the I-V
characteristic for the S1T2410B02 tone ringer. Curve A is a plot with R_SL < 6.8kΩ and shows an increase in the
current drawn up to the initiation voltage V_SI. After initiation, the I-V characteristic remain unchanged. Curve C
illustrates the effect of increasing R_SL above 6.8kΩ initiation current decreases, but is unchanged after triggering.
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