TDA7350 STMicroelectronics, TDA7350 Datasheet - Page 17

• Manufacturer Part Number: TDA7350
• Description: IC AMP AUDIO PWR 22W MULTIWATT11
• Manufacturer: STMicroelectronics
• Type: Class ABr

Specifications of TDA7350

• Output Type: 1-Channel (Mono) or 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 22W x 1 @ 3.2 Ohm; 11W x 2 @ 2 Ohm
• Voltage - Supply: 8 V ~ 18 V
• Features: Depop, Short-Circuit and Thermal Protection, Standby
• Mounting Type: Through Hole
• Package / Case: Multiwatt-11 (Vertical, Bent and Staggered Leads)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TURN-OFF
A turn-off pop can occur if the st-by pin goes low
with a short time constant (this can occur if other
car radio sections, preamplifiers,radio.. are sup-
plied through the same st-by switch).
This pop is due to the fast switch-off of the inter-
nal current generator of the amplifier.
If the voltage present across the load becomes
rapidly zero (due to the fast switch off) a small
pop occurs, depending also on Cout,Rload.
The parameters that set the switch off time con-
stant of the st-by pin are:
The time constant is given by :
T Csvr 2000 // Rext + Cst-by 2500 // Rext
The suggested time constants are :
T > 120ms with C
T > 170ms with C
If Rext is too low the Csvr can become too high
and a different approach may be useful (see next
section).
Figg 40, 41 show some types of electronic
switches ( P compatible) suitable for supplying
the st-by pin (it is important that Qsw is able to
saturate with V
Also for turn off pop the bridge configuration is su-
Figure 40
Figure 41
(Rext)
the st-by capacitor (Cst-by)
the SVR capacitor (Csvr)
resistors connected from st-by pin to ground
CE
out
out
150mV).
=1000 F,R
=2200 F,R
L
L
= 4ohm,stereo
= 4ohm,stereo
perior, in particular the st-by pin can go low faster.
GLOBAL APPROACH TO SOLVING POP
PROBLEM BY USING THE MUTING/TURN ON
DELAY FUNCTION
In the real case turn-on and turn-off pop problems
are generated not only by the power amplifier,but
also (very often) by preamplifiers,tone controls,ra-
dios etc. and transmitted by the power amplifier to
the loudspeaker.
A simple approach to solving these problems is to
use the mute characteristics of the TDA7350.
If the SVR pin is at a voltage below 1.5 V, the
mute attenuation (typ)is 30dB .The amplifier is in
play mode when Vsvr overcomes 3.5 V.
With the circuit of fig 42 we can mute the amplifier
for a time Ton after switch-on and for a time Toff
after switch-off.During this period the circuitry that
precedes the power amplifier can produce spuri-
ous spikes that are not transmitted to the loud-
speaker. This can give back a very simple design
of this circuitry from the pop point of view.
A timing diagram of this circuit is illustrated in fig
43. Other advantages of this circuit are:
- A reduced time constant allowance of stand-by
pin turn off.Consequently it is possible to drive all
the car-radio with the signal that drives this pin.
-A better turn-off noise with signal on the output.
To drive two stereo amplifiers with this circuit it is
possible to use the circuit of fig 44.
TDA7350
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