LA8519M Datasheet, PDF (22/29 Pages) Sanyo Semicon Device – I/O Switch/Voice Signal-Processing IC for Cordless Telephones

LA8519M
• VOX circuit
(1) The VOX circuit detects whether there is conversation or not. When the signal level in the VOXA input block
(when the application constants in the application circuit diagram are used) becomes over about –42 dBV, the
VOX output pin (pin 29) goes low. The detection level can be set by setting the gain of the VOX input amplifier
with resistors R1 and R2.
(2) This circuit can be used as a waveform shaping circuit if VOX-RCT (pin 16) is connected to V_CC, i.e. if pin 16 is
set to the high level. Thus this circuit can also be used to recognize a 400 Hz beep tone. In this mode, there is no
need to connect a capacitor to pin 16.
VOXA-IN
+
–
13
14
R2
R1
RECT CMP
29
VREF
15
VOX-RCT
16
+
A13134
• Power amplifier circuit applications (The component values are for reference purposes only.)
C3
PWR-VCC 28
PWR-OUT 27
PWR-GND 26
C4
+
C2
+
C5
C1
62 kΩ
PWR-NF 25
PWR-VREF 24
PWR-IN 23
PWR-MONI 22
2 kΩ
+
C6
0.22 µF
C1: 0.1 µF
SP
C2: 0.1 µF
C3: 0.1 µF
C4: 220 µF
C5: 100 to 470 µF
C6: 220 µF
SP: 8 to 32 Ω
• Voltage gain: 20 to 30 dB
• A frequency characteristics adjustment capacitor cannot
be attached to the feedback resistor.
Note: The power amplifier output goes to the high-impedance state in the muted state,
i.e. when address 3F has been set to the off state.
A13135
• Power amplifier phase compensation capacitors
Of the external components, the capacitors C1 between pin 27 (output) and pin 26 (ground) and C2 between pin 27
and pin 28 (V_CC) are power amplifier phase compensation capacitors. If these components are separated from their
pins in the PCB layout, their phase compensation effect may be reduced and high-frequency oscillation may occur.
We therefore strongly recommend using a layout in which the capacitors C1 and C2 are located as close as possible
to their respective IC pins. In particular, C1, which is connected to ground, should be given priority in positioning
close to the IC. Note that phase compensation not with capacitors alone, but with series resistors (on the order of 1
to 2.2 Ω) inserted is also possible. While this can increase the phase compensation effect, since it increases the
parts count, we recommend using capacitors only. However, we do recommend phase compensation with resistors
inserted if, due to the details of the layout, the power amplifier is subject to oscillation.
Also note that the ceramic capacitor C3 between pins 26 and 28 has only a minimal phase compensation effect on
normal power amplifiers, so is not required. However, there are cases where it does have a large effect due to the
pattern layout, so we recommend creating a dummy pattern for this capacitor and handling it as a reserve
component.
No. 6471-22/29