TEA7530 データシートの表示（PDF） - STMicroelectronics
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TEA7530 Datasheet PDF : 11 Pages
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TEA7530
Amplifier DC Supply
In transmission mode, the supply voltage is con-
trolled by the internal shunt DC regulator. For this
reason, the TEA7530 should be supplied from a
current source (see: supply considerations).
An antidistortion system is embodied which pro-
vides AGC control to avoid loudspeaker distortion
under current-limited conditions.
AGC Circuit action
When the supply VLS is insufficient, the voltage at
pin 8, falls below the reference voltage 1.2V, re-
sulting in transistor (TR) being switched off, re-
sulting zero current flow in resistor R. This state
enables the gain control system. Under these
conditions, the shunt DC supply will switch at a
rate determined by the time constant of the RC
network on pin 2.
This switching action accomodates normal
speech characteristic under low supply condi-
tions.
The AGC will be switched ON when the level on
Pin 2 is greater than a reference voltage of 0.4V.
Supply Considerations
a) Current MODE - Pin 8 is open (VLS = VLS1) or
Figure 11
connected to ground with an external resistor
(Rext) higher than 16KΩ. The typical value of VLS
is :
VLS
The
=A1G.2CVs4e0c.t5ioK(nΩ2is7+Kw(Ωo2⁄r7k⁄KiRnΩEgX⁄ aT⁄ sR) EdXeTs)c.ribed
in
the
previous paragraph.
b) Voltage MODE - Pin 8 is shorted or connected
to GND with a resistor (REXT) lower than 16KΩ. In
this condition the circuit must be supplied with a
DC voltage of 3 to 5.5V. In this case the AGC
section is permanently ON. Pin 2 must be shorted
to GND (in voltage mode only) to avoid perma-
nent attenuation of the signal at audio input
PIN FUNCTIONS
PIN 1: GND.
PIN 2: AUTOMATIC GAIN CONTROL FILTER
The antidistortion system response is adjusted by
the R-C network on this pin.
The AGC will be switched ON when the level on
pin 2 is greater than a reference voltage of 0.4V,
the RC-network charges (current source ON) or
discharges (current source OFF) according to
supply voltage.
6/11
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