TDA7294S_05 Datasheet, PDF (6/16 Pages) STMicroelectronics – 100V - 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY

TDA7294S
Table 6. Application Suggestions (continued)
COMPONENTS
C4
SUGGESTED
VALUE
10µF
PURPOSE
ST-BY TIME
CONSTANT
C5
22µFXN (***)
BOOTSTRAPPING
C6, C8
C7, C9
1000µF
0.1µF
SUPPLY VOLTAGE
BYPASS
SUPPLY VOLTAGE
BYPASS
(*) R1 = R3 for pop optimization
(**) Closed Loop Gain has to be ≥ 26dB
(***) Multiply this value for the number of modular part connected
Figure 5. Slave function: pin 4 (Ref to pin 8 -V_S)
LARGER THAN
SUGGESTED
LARGER ST-BY
ON/OFF TIME
SMALLER THAN
SUGGESTED
SMALLER ST-BY ON/
ON/OFF TIME;
POP NOISE
SIGNAL
DEGRADATION AT
LOW FREQUENCY
DANGER OF
OSCILLATION
-V_S +3V
MASTER
-V_S +1V
UNDEFINED
SLAVE
-V_S
D98AU821
Note:
If in the application, the speakers are connected via long wires, it is a good rule to add between the output
and GND, a Boucherot Cell, in order to avoid dangerous spurious oscillations when the speakers terminal
are shorted. The suggested Boucherot Resistor is 3.9Ω/2W and the capacitor is 1µF.
4 Introduction
In consumer electronics, an increasing demand has arisen for very high power monolithic audio amplifiers
able to match, with a low cost, the performance obtained from the best discrete designs.
The task of realizing this linear integrated circuit in conventional bipolar technology is made extremely dif-
ficult by the occurence of 2^nd breakdown phoenomenon. It limits the safe operating area (SOA) of the pow-
er devices, and, as a consequence, the maximum attainable output power, especially in presence of highly
reactive loads. Moreover, full exploitation of the SOA translates into a substantial increase in circuit and
layout complexity due to the need of sophisticated protection circuits.
To overcome these substantial drawbacks, the use of power MOS devices, which are immune from sec-
ondary breakdown is highly desirable. The device described has therefore been developed in a mixed bi-
polar-MOS high voltage technology called BCDII 100.
4.1 Output Stage
The main design task in developping a power operational amplifier, independently of the technology used,
is that of realization of the output stage. The solution shown as a principle shematic by Fig.5 represents
the DMOS unity - gain output buffer of the TDA7294S.
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