LA8519M Datasheet, PDF (17/29 Pages) Sanyo Semicon Device – I/O Switch/Voice Signal-Processing IC for Cordless Telephones

LA8519M
Usage Notes
Speech Network Circuit Block
• External driver transistor
Line
7.5kΩ
R3
C2
+
620Ω _220µF
48
47
VL S-VCC
51Ω
3.3kΩ
Tr
49 TOI
8200pF
8.2kΩ
82Ω R1
82Ω
1.3kΩ
R2
8.2Ω
C1
50 TOO
51 BN1
LA8519M
5.6kΩ 1.8kΩ
52 BN2
6800pF
Figure 1
A13123
Since the IC includes a built-in power amplifier, due to the allowable power dissipation limits, include a heat
dissipation transistor as shown in figure 1, and dissipate the circuit current outside the IC. Set the allowable power
dissipation for R1 and R2 according to the maximum expected circuit current. (The values shown are for reference
purposes only.)
Note: If oscillation occurs due to the load state between VL and ground, insert the capacitor C1 (about 0.1 µF)
shown in the figure.
• Changing the DC resistance
The DC resistance can be modified by using a variable resistor for R2 in figure 1. (See the figure below.)
Note: Note that changing R2 will also change the transmitter gain and the balancing network conditions.
• Determining the AC impedance
The AC impedance is basically determined by R3 (620 Ω) and C2 (220 µF) shown in figure 1 above page. Since in
actual operation there will be other AC loads in addition to the speech network, adjust the total AC impedance for
the whole system in combination with the speech network impedance.
Note: Note that if R3 is changed, the DC resistance will change as well.
Line Voltage vs. Line Current
12
Power supplied: V_CC = 5 V
11
Power supplied: R2 = 10 Ω
10
Power off: R2 = 10 Ω
9
Power supplied: R2 = 8.2 Ω
8
Power off: R2 = 8.2 Ω
7
6
Power supplied: R2 = 6.8 Ω
5
Power off: R2 = 6.8 Ω
4
3
2
10 20 30 40 50 60 70 80 90 100 110 120 130
Line current — mA
No. 6471-17/29